LEE- Tekstil Mühendisliği Lisansüstü Programı

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http://hdl.handle.net/11527/19465

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Akrilik filament ipliğin tekstüre edilmesi

(Lisansüstü Eğitim Enstitüsü, 2021) Mutlu, Aras ; Demir, Ali ; 709844 ; Tekstil Mühendisliği

Akrilik elyaf, en eski sentetik tekstil elyaflarından biridir. 2000 yılında dünya elyaf kullanımının yaklaşık %5'lik kısmını akrilik elyaf oluştururken bu oran 2020 yılında %1 mertebesine gerilemiştir. Üstelik birçok elyafın kullanım miktarı artmakta olmasına rağmen akrilik elyafta düşüş trendi devam etmektedir. Tüm bu akrilik elyaf tüketimi elyaf (kesikli lif) formundadır. Filament formunda akrilik ipliğin tarihçesinin 1950'li yıllara kadar dayanmasına ve birçok üreticinin akrilik filament iplik üretimine başlamış olmasına rağmen çeşitli nedenlerle ticari olarak yaygınlaşması yakın zamana kadar mümkün olmamıştır. Bu nedenle, akrilik filament ipliğin tekstüre edilmesi üzerine yaygın bir bilimsel literatür ya da ticari bilgi bulunmamaktadır. Aslında akrilik elyaf üretimi esnasında uygulanan "kıvırcıklandırma" işlemi, termomekanik tekstüre yöntemlerinin tüm temel aşamalarına sahiptir. Tüm dünyada kişi başına düşen elyaf tüketimi artarken filament iplik üretiminde de önemli artış yaşanmaktadır. Yıllık filament iplik üretimi çok daha hızlı bir artış göstermektedir ve 2013 yılından itibaren kesik elyaftan üretilen ipliklerin üretim miktarını da geçmiştir. Filament iplik, enerji ve iş gücü yoğun, detaylı ve uzun süren iplik eğirme proseslerini ortadan kaldırmasının yanı sıra final ürüne kazandırılan mükemmel fiziksel özellikler ile de hem düşük maliyetli hem de yüksek performanslı ürünler elde edilebilmesine olanak sağlamaktadır. Ancak filament ipliklerin en önemli dezavantajlarından biri düz ve bükümlü formda parlak ve suni bir görüntüye sahip olmasıdır. Bu haliyle birçok kullanım alanı için kabul görmeyen bir ürün halindedir. Tekstüre işlemi, filament ipliklerin daha doğal görünüm ve tutuma sahip hale getirilmesi için uygulanan bir prosestir. Tarih boyunca gerçek büküm-büküm açma, yalancı-büküm, bıçak sırtı, dişli çark, örme-sökme, yığma kutusu gibi termomekanik, hava-jeti gibi mekanik ve bunların yanı sıra bikomponent, kimyasal ile tekstüre gibi yöntemler çalışılmış olsa da günümüzde en yaygın olarak kullanılan iki yöntem yalancı-büküm ve hava-jeti ile tekstüre yöntemleridir. Polyester, poliamid, polipropilen gibi termoplastik liflerin tekstüre edilmesine yönelik yaygın literatür bulunmaktadır. Akrilik filament iplik ise fiziksel, kimyasal ve termal özellikler açısından bahsi geçen termoplastik liflere göre ayrıştığı için bu malzemenin tekstüre edilmesine yönelik özel araştırmaların gerçekleştirilmesi önem kazanmaktadır. Akrilik filament iplik, diğer sentetik ipliklere kıyasla ultraviyole ışınlarına, kimyasallara ve mikroorganizmalara karşı daha iyi bir dayanım gösterirken, yüksek ışık ve hava şartlarına karşı renk haslığı, rezilyans, boyutsal kararlılık gibi özellikleriyle de ön plana çıkmaktadır. Ayrıca akrilik kesik elyaftan üretilen ipliklere göre daha yüksek mukavemet ve kumaşa dönüştürüldükten sonra daha yüksek aşınma dayanımı ve boncuklanma özelliklerine sahip olacaktır. Akrilik filament iplik halihazırda kullanıldığı bükümlü haliyle kendisine tente, halı, dikiş ipliği gibi kullanım alanları bulabilse de tekstüre edilmemiş filament ipliklere özgü suni görüntüsü nedeniyle potansiyelinin altında bir kullanımı olduğu değerlendirilmektedir. Bu iplik için uygun tekstüre proses şartlarının belirlenerek sonraki tekstil proseslerinde işlenebilir ve kabul edilebilir fiziksel özelliklere sahip akrilik filament tekstüre iplikler elde edildiğinde çok daha yaygın bir şekilde kullanımı mümkün olacaktır. Bu çalışma kapsamında, gerçek büküm-büküm açma, yalancı-büküm, örme-sökme, sıcak hava-jeti, soğuk hava-jeti ile tekstüre yöntemleri incelenmiş, tüm yöntemlerle ilgili kritik noktalar belirlendiği gibi yalancı-büküm tekstüre ve hava-jeti ile tekstüre yöntemlerinde yürütülen deney tasarımı ve sonrasında gerçekleştirilen istatistiksel analiz ile optimum proses şartları belirlenmeye çalışılmıştır. Elde edilen sonuçlar, akrilik filament iplikten yeni ticari ürünler oluşturulmasına yardımcı olacağı gibi bu iplik için zayıf olan literatür bilgisinin genişletilmesinde ve potansiyel yeni çalışmalara temel oluşturulmasında yararlı olacaktır.
Bimodal fonksiyonel dokusuz hava filtrelerinin üretimi ve geçirgenlik özelliklerinin karakterizasyonu

(Lisansüstü Eğitim Enstitüsü, 2023-12-14) Toptaş, Ali ; Kılıç, Ali ; 503192806 ; Tekstil Mühendisliği

Nüfus artışı ve hızlı sanayi gelişimi nedeniyle temiz havaya olan ihtiyaç artmaktadır. Katı partikül maddeler, organik maddeler ve salgın hastalıklara yol açan ajanları (mikrop, virüs vb) içinde barındıran kirli hava, insan sağlığı için önemli bir tehdit oluşturmaktadır. Mikro ve nano ölçekteki PM10, PM2.5, PM1.0 ve PM0.3 olarak kategorize edilen Partikül Maddeler (PM), hava kirliğinin kaynaklarıdır. Partikül maddeler solunum sisteminde alveollere kadar nüfuz edebildikleri için kanser dahil çeşitli hastalıklara yol açabilmektedir. Dünya Sağlık Örgütü'ne (DSÖ) göre, her yıl 10 mikrometreden daha küçük parçacıkları içeren kirli havaya uzun süre maruz kalan 4 milyondan fazla kişi hayatını kaybetmektedir. Bu nedenle, bu parçacıkların havadan uzaklaştırılması/filtrelenmesi gerekmektedir. Filtreleme işlemi, havanın, nano- veya mikrogözeneklere sahip filtre yüzeylerinden geçirilerek, partikül maddelerin ayrıştırılma süreci ile tanımlanmaktadır. Özellikle hastanelerdeki yoğun bakım üniteleri, ameliyathaneler ve hastaların bulunduğu tüm ortamlarda havayı filtrelemek için HEPA veya ULPA filtreler kullanılmaktadır. Bunun yanında, yüksek seviyede PM bulunan ortamlarda çalışan kişilerin yüz maskelerini kullanmaları büyük önem arz etmektedir. Nano- ve mikro gözenekli dokusuz yüzeyler, solunan havanın zararlı etkilerini en aza indirmek için filtreler ve yüz maskeleri gibi filtrasyon yüzeylerinin üretiminde kullanılmaktadır. Nanolifli yüzeylerdeki gözenek boyutları da nano seviyelerdedir, dolayısıyla bu tür filtrelerle nano boyuttaki PM'leri filtrelemek mümkündür. Bu nedenle, hava filtrelemesi için nanolifli filtreler, mikrolifli filtrelere göre daha yüksek filtrasyon verimliliği (ղ) sunarlar. Çok ince nanoliflerden (65 nm'nin altında) meydana gelen filtre yüzeyleri, nanoliflerin yoğun bir şekilde paketlenmesi ile yüksek katılık değerine ulaşabilmektedir. Bu durum, havanın filtre yüzeyinden geçmesini zorlaştıraraak basınç düşüşü değerini artırıp, filtre yüzeyinin hızla tıkanmasına ve partiküllerin etkili bir şekilde filtrelenmesine engel olmaktadır. Bu durum, filtre yüzeyinin hızla tıkanarak havanın filtre yüzeyinden kolay bir şekilde geçmesine engel olur. Filtre yüzeylerinin hızlı bir şekilde tıkanmasını ve yüksek basınç düşüşü değerleri göstermesini engellemek için, nano- ve mikroliflerin biraraya gelerek oluşturduğu bimodal (Tez başlığında yer alan bu terim tüm çalışma boyunca yaygın kullanılacak bir terimdir. Filtre yüzeyinde iki farklı ortalama kalınlığa (çapa) sahip liflerin mevcut olduğunu ifade eder.) filtre yüzeyleri ön plana çıkmaktadır. Bimodal filtre yüzeylerinin yapısında nano- ve mikroliflerin birlikte bulunmasından dolayı, hava akış değerleri geniş bir Knudsen aralığında yer almaktadır. Bu sayede filtre yüzeyinden hava akışı daha kolay gerçekleşir. Filtre yüzeyinde mukavemeti daha yüksek olan mikroliflerin varlığı filtre yüzeyinin mekanik dayanıklılığını artırmaktadır. Bimodal yapıdaki yüzeyler kullanılarak, yüksek ղ, düşük basınç düşüşü (∆P) ve yüksek mekanik dayanıklılığa sahip filtre yapıları elde edilir. Literatürdeki bimodal filtre yapısı üzerine yapılan ilk çalışmalar genellikle simülasyon veya teorik hesaplamalara dayanmaktadır. Bimodal lif üretimine yönelik ilk çalışmalar, eriyikten üfleme (MB) yöntemi kullanılarak elde edilmiştir. Eriyikten üfleme yöntemini kullanan çalışmalarda, farklı erime sıcaklıklarına ve molekül ağırlıklarına sahip iki farklı polimerin ayrı ayrı ekstrüderlerden, tek bir ekstrüderden veya iki polimerin düze deliğinde buluşmasıyla elde edilen denizde adacık (Island in the sea) tipi liflerden oluşan yüzeylerin elde edildiği gösterilmiştir. Ayrıca literatürde, bimodal yapıların, kalın lif katmanları ve ince lif katmanlarının tabakalı bir şekilde oluşturulduğu çalışmalar da bulunmaktadır. Bu konudaki en dikkat çekici olan çalışmalar, yapısında nanonet içeren çalışmalardır. Bunlara ek olarak, literatürde elektro-üretim ve melt-blowing (MB) yöntemlerinin kombinasyonuyla filtre yüzeyi oluşturan bimodal çalışmalar da bulunmaktadır. Bu çalışmalarda çeşitli polimerler kullanılmaktadır. Çözeltiden üretilen lifli yüzeyler, genellikle poliviniliden florür (PVDF), poliakrilonitril (PAN), termoplastik poliüretan (TPU), poliamid-6 (PA-6), poliamid-6.6 (PA-6.6), polivinil alkol (PVA), politetrafloroetilen (PTFE) gibi sentetik polimerlerden veya jelatin, kolajen, kitosan, karboksimetil selüloz gibi doğal kökenli polimerik malzemelerden elde edilebilir. MB yöntemi kullanılarak eriyikten elde edilen lifli yüzeyler ise polyester (PET), polipropilen (PP), polibütilen tereftalat (PBT), polilaktik asit (PLA) gibi çeşitli termoplastik polimerlerden veya cam yünü gibi doğal kökenli malzemelerden elde edilebilir. Bu çalışma kapsamında öncelikle PVDF'ten üretilen nanoliflerin malzeme ve üretim sistemi parametrelerinin optimizasyonu üzerinde durulmuş ve PVDF bazlı elektret (Bu çalışma kapsamında elektret kelimesi yaygın kullanılmaktadır. Bu terim polimerlerin yüzeylerine uygulanan harici etkenler nedeniyle polimer zincirindeki serbest uçların polimer yüzeyine yönlenmesiyle oluşan negatif veya pozitif yüklerle yüklenmesini ifade eder.) nanolifli yüzeylerin elektro-üfleme yöntemi ile üretimi optimize edilmiştir. Deneysel parametreler, Taguchi üç düzeyli L9 ortogonal tasarımı kullanılarak sistemli bir şekilde oluşturulmuş ve ANOVA ile istatistiksel olarak analiz edilmiştir. Bu bağlamda, incelenen parametreler çözelti konsantrasyonu, hava basıncı ve elektrik alan olmuştur. Bu parametreler arasında, lif çaplarını en çok etkileyen faktörlerin çözelti konsantrasyonu ve elektrik voltajı olduğu belirlenmiştir. En ince nanolifli filtre yüzeyini (124±71 nm) üreten optimum parametreler, sırasıyla %9 çözelti konsantrasyonu, 2 bar hava basıncı ve 30 kV elektrik voltajıdır. Ayrıca, numunelere uygulanan korona deşarj işlemi, kalite faktörlerinde %70'in üzerinde bir iyileşmeye neden olmuştur. Elektret filtre üretimine yöntelik araştırmalarımızda korona deşarjı ile polarizasyonunun oluşum mekanizmasını çözümlemek amacıyla yapılan bir başka çalışmada PVDF bazlı nanolif nanojeneratörler, elektro-üfleme (EB) yöntemi kullanılarak üretilmiştir. Bu çalışmada uygulanan elektrik voltajı ve hava basıncının, lif morfolojisi ve piezoelektrik özellikleri üzerindeki etkileri araştırılmıştır. 2 bar basınç altında üretilen numuneler, 3 bar basınç altında üretilen numunelerden daha ince lif çaplarına sahip olmuştur. Ayrıca, β-faz yüzdesi, uygulanan voltajın artmasıyla artmıştır. En yüksek β-faz yüzdesi, 2 bar hava basıncı ve 30 kV ile üretilmiş numunede gözlemlenmiştir. En yüksek piezoelektrik etki, 224±60 nm ortalama lif çapına sahip numuneden elde edilmiş, β-faz içeriği %88 olmuştur. Sonuç olarak elektro-üfleme yöntemi ile üretilen PVDF nanoliflerin β-faz ve piezoelektrik etkisini maksimize etmek için polarizasyonun en etkin mekanizma olduğu belirlenmiştir. Bu tez kapsamında yapılan, farklı oranlarda PVDF ve polietilen glikol (PEG) polimerlerini içeren çözeltilerden elektro-üfleme yöntemi ile nanolif/nanonet yapılı filtrelerin üretildiği bir başka çalışmada, çözelti içeriğindeki suda çözünebilir, düşük molekül ağırlıklı PEG içeriğinin artırılması ve üretilen yüzeylere, bu tez kapsamında özgün olarak tasarlanan, su banyosu işlemi uygulanarak yapıdaki PEG'in uzaklaştırılmasıyla, lif çapları azaltılmış ve daha gözenekli yapılar elde edilmiştir. En yüksek PEG içeriğine sahip PVDF:PEG (3:7) numunesi, 170 nm ve 50 nm civarında ortalama çaplara sahip öbekler halinde nanolif/nanonet benzeri yapılar sergilemiştir. Geliştirilen bu numunenin ղ değerinde, korona deşarj işlemi sonrasında %3.6'lık bir artış, kalite faktöründe ise %60'lık bir iyileşme gözlemlenmiştir. Sonuç olarak, PVDF:PEG (3:7) numunesi, çok yüksek bir ղ değeri (%99.57), oldukça düşük bir ∆P (158 Pa) ve bu sayede tercih edilen bir kalite faktörü (QF) 0.0345 sunan nanolif yapılı filtrelerin başarılı bir şekilde üretilebileceğini göstermiştir. Tez kapsamında filtre yüzeyinde nano- ve mikroliflerin homojen dağılımı veya katmanlı kullanımı yoluyla bimodal filtreler elde edilmiştir. Çalışmada, bimodal yapısal tasarımın etkisi, eriyikten üfleme (MB), çözeltiden üfleme (SB) ve elektro-üfleme (EB) yöntemleriyle üretilen çeşitli katman konfigürasyonlarında ve farklı çaplardaki liflerden oluşan yüzeylerin filtrasyon performansları karşılaştırılmıştır. Filtre numunelerinin gramajı 30 gsm olarak korunurken, 4 katmanlı filtre (4L) yapılarının kullanılması, tek katmanlı numunelere (L) kıyasla hava geçirgenliğinin artmasıyla sonuçlanmıştır. Bu şekilde oluşturulan 4L numunesi 148 Pa basınç düşüşü değeri ve en yüksek filtrasyon verimliliğine (%99,52) sahip olmuştur. Ayrıca 4L yapısındaki MB katmanının, SB nanoliflerinin MB'ye homojen bir şekilde dahil edilmesiyle elde edilen bimodal yüzeyler (BM) katmanı ile değiştirilmesi, filtrasyon verimliliğini %99,61'e yükseltmiş ve ΔP neredeyse aynı kalmıştır. PVDF:PP masterbatch kullanılarak eriyikten üfleme yöntemi ile üretilen filtre yüzeyine uygulanan korona deşarj işlemi ile, işlemi ile elde edilen bimodal yapıdaki 4BML numunesinde en yüksek filtrasyon verimliliği (%99,99) elde edilmiştir. Bu numunelerde bir ay sonrasında dahi filtrasyon verimliliği %99,90 olarak korunmuş; bu durum, elektret filtrelerinde bimodal lif dağılımının en yüksek avantaj sağladığını göstermiştir. PVDF nanoliflerin yapısına eklenen katkı malzemelerinin filtre yüzeyinin morfolojik yapısına etkisinin incelendiği çalışmada, Al(NO3)3.9H2O, NaCl, LiCl, KCl gibi katkı maddelerinin PVDF çözeltisine %1 ağırlık oranında ilave edildiği çözeltilerden nanolifli yüzeyler üretilmiştir. Al(NO3)3.9H2O katkı malzemeli numuneden en ince lif çapı ve en düzgün lif morfolojisi elde edilmiştir. Ayrıca, korona deşarjı işleminden sonra %99,95 ղ değeri ve 195 Pa ∆P değerleri elde edilmiştir. Tüm bu ölçümler sonucunda, Al(NO3)3.9H2O numunesinin ince lif çapı ve yüksek filtrasyon verimliliği ile PVDF için uygun bir katkı malzemesi olduğuna karar verilmiştir. Farklı triboelektrik serilerde yer alan PVDF ve PA-6 polimerlerinden üretilen nanoliflerinden elde edilen katmanlı yapıların incelendiği diğer bir çalışmada, triboelektrik etki ile birlikte bimodal etkinin filtrasyon performansına etkileri incelenmiştir. Ortalama 60 nm çapındaki PA-6 nanolifleri ile 176 nm çapındaki PVDF nanoliflerinden elde edilen bimodal filtre yapıları, korona deşarjı sonrasında %99,997 ղ değeri ve 193 Pa basınç düşüşü değerine ulaşmıştır. Dört hafta sonra İPA yöntemi ile deşarj işlemine tabi tutulan numuneler, filtrasyon testi sonrasında hem 0.26 kV yüzey potansiyeli hem de %99,829 ղ değeri ile yüksek filtrasyon ve yüksek triboelektrik özelliğini muhafaza ettiği kanıtlanmıştır. Erişilen bu filtrasyon değerleri tez kapsamında elde edilen ticari olarak değerlendirilebilecek en önemli çıktıyı oluşturmaktadır.
Composite nanofiber patches for topical drug delivery systems

(Graduate School, 2021-04-19) Barbak, Zarife ; Karakaş, Hale ; 503122805 ; Textile Engineering ; Tekstil Mühendisliği

Nanofibers are ultrafine, continuous, solid state textile fibers that have diameters less than 1 micrometre. Nanofibers possess remarkable properties such as high interconnected porosity, specific surface area, ability to imitate the Extra Cellular Matrix (ECM) and potential carrier for drug delivery. Due to these fascinating properties, nanofibers are attractive candidates for medical applications for instance wound dressings, tissue scaffolds and artificial blood vessels. Electrospinning is the simplest and most practical among all methods to produce fine fibers with diameters ranging from micrometres to nanometres. Basic electrospinning equipment includes a high voltage source, a solution feeding unit, a syringe with a tip and a collector. At first, high voltage is applied to the polymer solution to produce an electrical field between the tip and the collector to shape the droplet on the tip as Taylor Cone. When the electrostatic force is higher than the surface tension of the polymer solution, polymer jet is ejected from the tip to the collector. Then, polymer jet reaches to collector following a spiral way by getting longer and thinner. Finally, nanoscale fibers are obtained on the collector. Topical drug delivery systems are composed of a formulation that applied to the skin directly to heal disorders or disease of the skin which guide/target pharmacological effect of the drug to the skin surface. Different pharmaceutical dosage forms can be used in topical drug delivery such as gels, creams, ointment, liquid preparation, sprays and solid powders. Electrospun nanofibers are excellent materials for drug delivery systems due to high interconnected porosity, high surface area, ability to imitate the Extra Cellular Matrix (ECM), potential carrier for drug delivery. Utilization of nanofibers in drug delivery systems is based on the principle that the high surface area of the nanofibrous formulation increases the dissolution rate of the drug. Compared with other dosage forms such as; liposomes, micelles and hydrogels, major advantages of nanofibers are increment in drug loading efficiency and loading capacity, low systemic toxicity and excellent stability. Furthermore, several drugs can be carried within nanofibers with high local drug concentration due to their excellent targeting and drug transportation ability in a safe way. Electrospinning offers the opportunity for direct loading of drugs or biological agents for instance antibacterial molecules, antibiotics, enzymes, growth factors, proteins, peptides, vitamins, DNA into the electrospun nanofibers. Poly (ε-caprolactone) (PCL), Poly Lactic Acid (PLA) and Poly (ethylene oxide) (PEO) were used as carrier polymers for drug delivery. PEO is a highly aqueous soluble polymer, that interacts with the body fluid quickly due to its hydrophilicity resulting in dissolution. PEO is widely used in the polymer matrix to enhance bioavailability and solubility of drugs because of its high aqueous solubility and unique properties in drug delivery applications. The compatibility of PCL and PLA with different types of drugs enables uniform drug distribution in the polymer matrix and the slow degradation rate makes them favourable for prolonged drug delivery systems. In recent years, various studies were reported on the fabrication of drug delivery systems, generated by electrospinning of PCL, PEO, PLA and their blends. PCL, PEO, PLA nanofibers or their blends were loaded with different drugs and biological agents such as; Niclosamide, Silver nanoparticles, Vitamin B12, Curcumin, Lysozyme, AgNO3, Metronidazole (MNA). Polymer blending is an effective approach to prepare functional nanofibers by incorporating the favourable properties of the component polymers. Furthermore, polymer blending facilitates the manipulation of physical, mechanical or biochemical properties of nanofibers. Hydrophilic/hydrophobic polymer blends have been electrospun into nanofibers to fabricate controlled DDS. The hydrophobic polymer forms the backbone structure and it degrades slowly, creating a long term but steady-state drug release. On the other hand, the hydrophilic polymer degrades with a more rapid process, faster than hydrophobic, which accelerates the drug release. In this study, hydrophilic water-soluble PEO was selected for the polymer matrix to enhance the solubility and bioavailability of insoluble SSD. The hydrophobic character of PCL and PLA offers a long period SSD release therefore hydrophilic PEO was blended with hydrophobic PCL and PLA. Thus, PCL/ PEO and PLA/PEO composite polymer matrix was used to provide both increased solubility and controlled release of SSD. Silver sulfadiazine (SSD) is a non-ionized, water-insoluble, topical agent with a wide range of antimicrobial activity that is affected both on bacteria and fungi. SSD is a sulfonamide based drug that is formed by the reaction of sulfadiazine with silver nitrate to form complex silver salt. SSD is used extensively in the topical treatment of infected burns. Silver sulfadiazine provides a long-term release of silver ions, whereas in the case of other silver salts, such as silver nitrate, large amounts of silver ions are released all at once. Thus, the use of SSD decreases the need for frequent application. This makes SSD a desirable and favourable agent since the frequent application is not always practical or possible for patients. However, the low aqueous solubility (3.4 mg/l at pH = 6.8) restricts the drug efficiency, bioavailability and potential antimicrobial activity of SSD thus its applications are limited. Drug solubility is an important issue since efficient drug release and antimicrobial efficiency is contributed just by decomposition of SSD to sulfadiazine and silver ions. Also, the solubility problem of SSD makes it difficult to be stabilized and incorporated into the polymer matrix. The aim of the thesis is to produce a novel SSD loaded topical drug delivery system by using advantages of electrospun nanofibers. Also, a new buffer, Water/Propylene Glycol/ Phosphoric Acid (82:16:2) was utilized to investigate the dissolution and release behaviour of SSD. Thereby SSD containing PCL/PEO and PLA/PEO composite nanofiber carriers were electrospun to achieve the enhancement in solubility, effective drug release and efficient drug loading of SSD. For this purpose, initially, the water-insoluble SSD was incorporated into highly aqueous soluble PEO to increase the solubility. Afterwards, the PEO+SSD solution was blended with PCL and PLA solution to produce composite PCL/(PEO+SSD) and PLA/(PEO+SSD) nanofibers and PCL/(PEO+SSD) casting films for topical drug delivery. SEM method was used to enable the observations of fiber defects and irregularities in the nanofibers structures and to measure the average fiber diameters of the nanofibers. The morphological characterization of the casting films was carried out by SEM and Optical Profilometer. Energy dispersive spectra (EDS) analysis was performed to confirm that the composite nanofibers and casting film which contain SSD, by detecting the Silver (Ag), Nitrogen (N), Sulphur (S) content of the nanofibers. Moreover, EDS-Mapping was carried out to show the distributions of these elements in the composite nanofibers and casting films. The stability of SSD in the fiber structure and the molecular interactions in the drug-free and drug loaded nanofibers were examined by Attenuated Total Reflectance Infrared (FTIR-ATR) Spectroscopy. The crystalline structure of the SSD loaded composite electrospun nanofibers were investigated with X-ray diffraction (XRD) analysis. Atomic Force Microscopy (AFM) was used to determine the surface roughness of the composite nanofibers. 3D AFM Images show the roughness structure of nanofibers. Water contact angle measurements were performed to evaluate the wettability properties of the fabricated nanofibers and casting films surfaces. In vitro drug release media and release conditions were optimized and the controlled drug release profile was obtained for 24 hours. Drug loading efficiency of the nanofiber formulations and casting film were calculated. To understand the SSD drug release mechanisms from SSD loaded formulations; Zero Order, First Order, Higuchi, Hixon Crowell and Korsmeyer-Peppas kinetics models were applied in the drug release profiles of the formulations. Drug release studies were also verified with conductivity measurement due to the conductive nature of SSD. Antibacterial activities of the composite nanofibers against gram-positive Staphylococcus aureus (S. aureus) and gram negative Pseudomonas Aeruginosa (P. aeruginosa) Escherichia coli (E. Coli) bacteria were performed for the period of 24, 48 and 72 hours according to disc diffusion test method. Also, the antibacterial activity of commercial SSD cream was tested for comparison with nanofiber formulations. Furthermore, antibacterial activity of the SSD loaded PCL/PEO and PLA/PEO nanofibers were examined with determining MIC and MBC values. Stability studies of the composite nanofibers were done for 3 and 6 months periods. Nanofiber samples were kept both at refrigerator conditions (+4ºC) and room conditions (25ºC ±2 and 65 % ±2ºC relative humidity) to evaluate stability of nanofiber patches. Stability tests were performed with calculating drug loading amount, cumulative drug release by UV absorption measurements and analysing surface morphology by SEM analysis. Finally, the cytotoxicity studies of the drug loaded and drug-free PCL/PEO and PLA/PEO nanofiber patches were done with using the cell viability assay (MTT assay).
Design and development of pva/hydrocortisone loaded xerogel nanofibrous mat for topical drug delivery

(Graduate School, 2023) Moussa, Hissam Ali Muhammad Ali ; Kayaoğlu Karagüzel, Burçak ; 807298 ; Textile Engineering Programme

Textile materials have always been utilized in the medical field. The unique properties they offer, biocompatibility and versatility are the major reasons behind that. They can be found in applications ranging from a simple bandage to full on blood vessels. Nanofiber-based textile materials are textile materials known for their high surface area and interconnected porosity. Nanofiber- based textile materials can be fabricated with a variety of methods yet; the most dominant method is electrospinning. Furthermore, in the recent years there has been a rise of interest in different materials as well such as; aerogels. Aerogels are porous materials that have unique properties that make them good candidates for drug careering and releasing. Aerogels can be made of different materials such as polymers, biopolymers and metal oxides but the most common types of aerogels are silica, carbon and metal oxide aerogels. The process of synthesizing aerogel consists mainly of three stages; gelation, aging and drying. The process of drying aerogels affects the synthesized aerogel greatly as you can have three different types of aerogels by just using a different drying technique. Xerogel is one of the types of aerogels and it is achieved by drying aerogels at ambient pressure. This study aimed to design and develop a PVA/hydrocortisone loaded xerogel electrospun mat for topical drug delivery. The silica xerogel was synthesized using TMOS as a silica precursor, Ammonium hydroxide as a catalyst and Methanol as a co-solvent. The xerogel was ball-milled into fine powder and had its surface area, pore size and volume analyzed. In addition to that, hydrocortisone was loaded into three different samples; one consisting of only xerogel, the second of only PVA nanofibrous mat and the third consisting of both xerogel and PVA nanofibrous mat. In vitro drug release analysis was carried out for all of these samples. PVA was chosen for its biocompatible properties and stability. SEM and EDAX analyses were carried out to investigate the surface of the fibers and elements existing in the samples respectively. In addition to that, FTIR analysis was performed to identify the different materials making up the nanofibrous mats. The synthesized silica xerogel had a surface area of around 505 m²/g, pore size of around 3.8 nm and a pore volume of 0.48 cm³/g. SEM images showed the hydrocortisone loaded xerogel inside the PVA nanofibrous mat and the EDAX analysis confirmed the existence of silicone in the samples due to the existence of silica xerogel as well as a high concentration of Carbon due to hydrocortisone. The hydrocortisone loaded xerogel showed a slow sustained drug delivery release behavior and around 69.3% of the loaded hydrocortisone was released in 25 days. The PVA/xerogel/hydrocortisone nanofibrous mat showed a similar drug release behavior with a release of around 79.2% of the hydrocortisone initially loaded with PVA was released in just 30 minutes. Demonstrating a conventional or retarded drug release behavior. Meanwhile, the PVA/hydrocortisone electrospun mat showed a completely different drug release behavior. Around 98.55% of the hydrocortisone initially loaded into the PVA. In conclusion, Silica xerogel as a drug carrier was successfully synthesized. It was loaded with hydrocortisone. Hydrocortisone loaded silica xerogel drug release was investigated as well as PVA/xerogel/hydrocortisone and PVA/hydrocortisone. The result of these three different sample types were collected and compared. Both hydrocortisones loaded xerogel and PVA/xerogel/hydrocortisone showed a slow sustained drug release behavior. Meanwhile PVA/hydrocortisone showed a retarded drug release behavior. These results suggest the capability of PVA/hydrocortisone load xerogel mat to work as a sustained/controlled topical drug delivery carrier.
Detection and classification of fabric defects with an innovative model and perspective

(Graduate School, 2025-01-24) Birsen, Sinem ; Sarıçam, Canan ; 503211815 ; Textile Engineering

The global textile and ready-wear industries represent a substantial and highly competitive sector of the global market, regulated by both quality and price. Fabric defects significantly impact the quality of ready-wear items. Likewise, undetected defects during traditional quality control processes can lower the value of fabrics. Consequently, detecting and classifying fabric defects becomes crucial for companies aiming to remain competitive in the market, whether through quality leadership or price rivalry. While the literature includes various studies on fabric defect detection and classification, these often rely on open-source or custom datasets and employ well-known deep learning architectures or propose novel architectures. However, no study to date has specifically accounted for the structural differences between woven and knitted fabrics when designing models for fabric defect detection and classification. To address this gap, the present study developed two new datasets – the Woven Fabric dataset and the Knitted Fabric dataset – and designed a novel deep learning architecture using Convolutional Neural Networks (CNNs). As the study method, an open-source dataset (TILDA) was first utilized to evaluate well-known architectures (VGG19, ResNet50, InceptionV3) and inspire the design of a custom CNN model. This custom architecture was then optimized using 3-factor, 2-level factorial design experiments to refine structural parameters. The model's performance was validated on three custom datasets (Woven, Knitted, and Woven-Knitted Fabric datasets). Subsequently, the hyperparameters affecting model performance were optimized using a 4-factor, 2-level factorial design, and the model was revalidated on both open-source and custom datasets. The model was evaluated using additional metrics, including recall, precision, specificity, and F1-score, demonstrating superior performance. Training performance was analyzed using Accuracy/Loss curves, confirming no signs of overfitting. Furthermore, confusion matrixes indicated the model's effectiveness and robustness in classifying different defect classes. The final model achieved 97.37% accuracy on the TILDA dataset, 97.73% accuracy on the Woven Fabric dataset, 96.92% accuracy on the Knitted Fabric dataset, and 98.36% accuracy on the Woven-Knitted Fabric dataset. The results including recall, precision, specificity, and F1-score all suppressed the expected criteria. These results demonstrate the model's capability to detect and classify fabric defects effectively, accounting for the structural differences between fabric types. Future studies will focus on expanding the datasets to include more fabric types and design samples, aiming to enhance the model's generalization ability and performance across different fabric domains. In conclusion, this study successfully identified a custom CNN model suitable for both woven and knitted fabric types, considering their structural differences. It lays the foundation for future research and industrial implementation in automated fabric quality control.
Developing filters for laundry machines to prevent microfiber release

(Graduate School, 2025-01-27) Sakmar, Gökçe ; Eniş Yalçın, İpek ; Sezgin, Hande ; 503221806 ; Textile Engineering

Microplastics (MPs) represent one of the most pervasive environmental pollutants in the modern era, with profound implications for ecosystems and human health. Among these, microplastic fibers originating from synthetic textiles during laundering are a particularly significant source of pollution. These fibers are released during washing cycles, bypass standard wastewater treatment processes due to their small size, and accumulate in aquatic, terrestrial, and even atmospheric environments. The resulting contamination poses risks not only to marine life but also to human health, as these fibers enter food chains, water supplies, and the air creatures breathe. If current trends persist, it is projected that over 22 million tons of synthetic fibers will be discharged into the environment by 2050, making this a critical environmental and public health issue. This thesis tackles the urgent problem of microplastic fiber pollution by focusing on the design, development, and optimization of textile-based filtration systems for household washing machines. The primary objective is to prevent the release of microplastic fibers into wastewater at their source. Unlike broad strategies that target post-discharge remediation or changes in textile production, this study emphasizes source reduction through effective filtration mechanisms integrated into washing machines. By leveraging advancements in textile engineering, the research identifies optimal materials, structural configurations, and designs that maximize microplastic fiber capture without compromising the functionality of washing machines. The thesis commences with a comprehensive review of the literature, which underscores the environmental significance of microplastics, particularly those derived from textiles. Microplastic fibers, which account for 34.8% of global microplastic pollution, are released during the washing of synthetic garments, such as polyester and polyamide, which constitute a significant portion of global textile production. A single wash cycle can shed hundreds of thousands to millions of fibers, which subsequently evade conventional wastewater treatment and infiltrate natural environments. These fibers are not only ingested by marine and terrestrial organisms but have also been detected in human food sources, drinking water, and the air, posing significant health risks such as oxidative stress, hormonal disruption, and even cancer. The environmental review also highlights the limitations of existing filtration systems. While some commercially available products, such as Guppyfriend bags and Cora Balls, capture a fraction of the fibers during laundering, they are insufficient to address the magnitude of the problem. Similarly, current wastewater treatment plants are only partially effective in removing microplastic fibers, especially the smallest particles. Consequently, integrating filtration systems directly into washing machines emerges as a practical and impactful solution. The experimental section of this thesis focuses on developing and testing woven textile-based filters designed specifically for household washing machines. Key variables examined include yarn structure, number of filaments, weave pattern, and weft density. These parameters were selected for their significant impact on filtration efficiency, durability, and compatibility with washing machine operations. Twelve fabric samples were produced using three different types of polyester yarns (monofilament, 36-filament multifilament, and 96-filament multifilament) and assessed for physical and functional properties, including basis weight, thickness, tensile strength, tear strength, stiffness, air permeability, and vacuum filtration efficiency. The samples were manufactured with plain and 2/2 twill weaves at two different weft densities (33 and 17 picks/cm). Additionally, surface morphologies were examined using scanning electron microscope (SEM). The results showed that increasing weft density led to higher basis weight and thickness across all samples. While twill weave fabrics generally exhibited slightly higher basis weight than plain weaves, the differences were not statistically significant. Twill weave fabrics consistently demonstrated greater thickness than plain weaves, attributed to the float structure in twill weaves that creates a looser and bulkier fabric. For tensile strength, plain weaves outperformed twill weaves due to their higher interlacing points, and an increase in yarn count further enhanced tensile strength. Regarding tear strength, loosely constructed fabrics with fewer interlacing points exhibited higher resistance in twill weaves as yarns moved and bunched together under force. Twill weave structures also had higher air permeability due to their more open structure. This research also explored broader considerations in filter design, including the influence of yarn type (monofilament vs. multifilament). Monofilament yarns, characterized by their smooth surfaces, exhibited advantages in terms of durability but were less effective at capturing smaller particles. In contrast, multifilament yarns, with their higher surface areas, demonstrated greater filtration efficiency but were prone to clogging and reduced throughput. The study concluded that an optimal filter design would likely involve a hybrid approach that combines the strengths of both yarn types. Stiffness tests confirmed that monofilament yarns exhibited greater rigidity than multifilament yarns, while air permeability tests showed higher values for twill weave and monofilament fabrics. These findings underscore the critical influence of fabric structure, yarn type, and weft density on both filtration efficiency and physical durability. Vacuum filtration tests revealed that plain weave fabrics had superior microplastic retention compared to twill weaves, owing to their compact structure and smaller pore sizes. The highest filtration efficiency, 96.60%, was achieved by the plain weave sample P36T-33-P, made with 36-filament yarns at a weft density of 33 picks/cm. This was followed by its twill counterpart P36T-33-T (92.87%) and the plain weave sample P36T-17-P (92.30%). Monofilament fabrics generally demonstrated filtration efficiencies below 90%. Results of the experiments revealed that woven filters with tighter structures and higher densities demonstrated superior microfiber retention capabilities. However, these configurations also may pose challenges such as increased pressure drop and reduced mechanical durability, necessitating a careful balance between filtration efficiency and operational practicality. The thesis further contextualizes its findings within the broader landscape of microplastic pollution mitigation. The research also emphasizes the need for regulatory action to mandate the inclusion of effective filtration systems in new washing machines, as proposed by the European Union's recent initiatives on plastic pollution. In addition to its scientific contributions, this thesis underscores the potential for academia-industry partnerships in addressing global environmental challenges. The research was conducted in collaboration with industry stakeholders, leveraging their resources and expertise to develop practical, scalable solutions. The findings are not only relevant to the academic community but also offer actionable insights for manufacturers, policymakers, and environmental organizations working to mitigate the impacts of microplastic pollution. In conclusion, this thesis marks an important progress in addressing microplastic pollution by presenting a scientifically supported and practical approach to a critical environmental challenge. By integrating textile engineering principles with real-world applications, the research offers a pathway for reducing microfiber emissions at their source, thereby contributing to the broader goal of preserving environmental and public health. The innovative filtration systems proposed in this study have the potential to transform household laundry practices and set a new standard for sustainable textile management.
Development of a novel drying algorithm for reducing dimensional change on cotton textiles during tumble drying

(Graduate School, 2023-01-20) Sükuti Acır, Ayşin ; Şahin, Umut Kıvanç ; 503191805 ; Textile Engineering

With the development of technology, the need for drying machines, which entered our lives, is increasing day by day as people are more involved in working life. People who want to save time and space and want to spend less effort for washing-drying processes are more attracted to this machine. Although the dryer appears to be a useful product in theory, it is a product that people use hesitantly. The main reason for this feeling is that drying machines shrink certain types of textiles, especially cotton-containing textiles. Within the scope of this study, a survey was conducted in order to determine the main source of the problem and to get to know the laundry habits of the users in daily life. According to the results of the survey, the shrinkage problem was determined and a phased experiment plan was designed by procuring fabric samples to simulate the textile products that the users most frequently observed shrinkage in daily life. Drying machines of different brands and models specified in the questionnaire were purchased and detailed algorithm analysis and shrinkage tests were applied. This study was carried out as a preliminary study and as a result, it was seen that there was no obvious difference between the shrinkage rates of the dryers available in the market, and all of them caused shrinkage at similar rates. It has been determined that slow drum rotation and high drum inlet temperature are the parameters that partially affect the shrinkage positively. Then, the test plan was designed considering the user conditions and the ½ Fractional Factorial Design of Experiment (DOE) study was planned. All data obtained as a result of experimental design tests and preliminary study were collected to form a mathematical model. The mathematical model was developed using the R program. By feeding 111 test data directly to the model, it is aimed to predict the shrinkage regardless of the dryer brand and model. The created model can make predictions with an accuracy rate of 97.5%. While creating the mathematical model, the importance and degree of influence of the parameters added to the model were determined and it was determined that the most important parameter affecting the shrinkage was the drum speed and drying time. Before the algorithm was designed, the shrinkage rates of the test samples were measured at different capacities periodically every 20 minutes in order to understand the development of shrinkage in the dryer and its relationship with humidity. By graphing the obtained data, it has been determined that there is a point where shrinkage gives the best results from the beginning of drying. This point is called the "Critical Moisture Point". In the periodic follow-up tests, it was determined that cotton textiles were not affected by any mechanical action and did not show shrinkage until the critical moisture point. On the contrary, it has been determined that when the textile, which comes from the washing machine with a certain amount of shrinkage, is put into the dryer, it releases itself and expands in size until it reaches the critical moisture point. It has been observed that when drying is continued after the critical moisture point, the textile starts to shrink and shrinks until the drying is complete. By combining the findings obtained as a result of all the experiments, an algorithm was designed to reduce the shrinkage rate during tumble drying of cotton textiles. Since the most important criterion in the algorithm design is the drum rotation, various iterations have been made by constructing drum stop and rotation durations at low speed and high speed. The purpose of the design is providing minimum mechanical drum movement. After drying in the 2800 RPM configuration until the critical humidity level, the configuration where the drum is slowed down to 1800 RPM and rotated for 2,5 minutes, then stopped for 7,5 minutes gives the lowest shrinkage rate among all trials. In order to ensure homogeneity and faster drying in the determined algorithm design, the system was supported with an additional heater. In the preliminary studies and as a result of the DOE tests, since the drying time directly affects the shrinkage, the shrinkage rate is further improved with the addition of an additional heater. While the lengthwise shrinkage rate of the reference Cotton Economic program was 9,2% in the knitted test sample and 2,1% in the woven test sample, the lengthwise shrinkage rate was measured as 6,6% in the knitted test sample and 1.6% in the woven test sample after the innovative algorithm design was developed. As a result of the new algorithm design, the lengthwise shrinkage rate has been improved by 28% in knitted textiles and 24% in woven textiles.
Development of e-textile based RFID enabled moisture sensor for wearable technologies

(Graduate School, 2024-01-12) Tekçin, Meltem ; Kurşun, Senem ; Paker, Selçuk ; 503162801 ; Textile Engineering

The applications of e-textiles are progressively expanding with the advancements in technology on a daily basis. Particularly versatile, wearable, flexible, light, thin and small electronic structures can be seamlessly employed across diverse domains, owing to the incorporation of textile materials. It is noteworthy that the sensors used in heart rate, respiratory rate monitoring, sweat and wetness detection used in health monitoring areas have recently consisted of textile-based electronic structures. Although there are many sensor structures used for wetness detection, the disadvantages of their usage are that these structures are generally rigid, hard, large and uncomfortable. Instead of these sensors, thin, flexible, light, textile-based sensors that are compatible with the user's movement are needed. On the other hand, studies indicate that the world population is gradually aging and urinary incontinence is becoming more common health problem in aging people. For these reasons, structures that detect urinary incontinence on time are needed for sick elderly individuals in terms of both personal comfort and health of users, and to alleviate the workload of their caregivers. This thesis aims to develop a textile-based, wearable, flexible, lightweight and comfortable RFID enabled moisture sensor structures that detects moisture and wetness while transmitting RF signals. Furthermore, the objective lies on printing techniques and ink formulations for crafting these sensors. This thesis consists of three articles, arranged by paying attention to the integrity of the scope. All of the articles given within the scope of the thesis are original and add innovation to the literature. In the articles, important and unique results of the thesis topic are discussed. In the first article, the design of a humidity sensor for wetness detection with respect to design criteria found in the literature research, was presented. The designed humidity sensor was printed on a polyamide-based taffeta label fabric using PEDOT:PSS conductive polymer by inkjet printing method. Ink characterizations were carried out to make PEDOT:PSS polymer suitable for inkjet printing. Sensor performance was measured in a closed humidity chamber where the relative humidity is controlled by an automatic humidifier against change in electrical resistance values of the sensor. Response and recovery times, sensitivity and repeatability of the sensor sensor were also measured. The humidity sensor was integrated onto the diaper to detect urinary incontinence. The variations in electrical resistance values of the sensor were analyzed by exposing it to varying quantities of an urine-like water solution, applied to the sensor integrated onto the diaper. The second article examines the UHF-RFID antenna performance of the proposed sensor structure. The sensor structure designed in this article was printed on polyamide-based taffeta label fabric using silver nanoparticle ink by pad printing method with different print passes. The importance of the sintering process was investigated and its effect on the results presented in the article was discussed. While the sintering process was applied to one group of sensor samples, the sintering process was not applied to the other group for comparison. UHF-RFID antenna performance of all samples was examined using a vector network analyzer. In addition to impedance measurements, gain and bending measurements of the textile antennas were carried out in order to show the antennas' flexibility. It has been determined that the sensor samples exposed to the sintering process operate as antennas. Finally, the third article encompassed the execution of an RFID sensor design capable of serving dual roles as both a sensor and an antenna. The proposed structure was designed using the CST Studio program, aiming to operate at 867 MHz according to European band. The RFID sensor was printed on polyamide-based taffeta label fabric by pad printing method using silver nanoparticle ink. A chip was integrated onto the structure so that the RFID sensor operates at the targeted frequency. The RFID sensor was integrated onto the diaper considering the real usage environment. RSSI measurements were made using both near-field RSSI measurement setup and highly antenna arrays. Additionally, the strength of the proposed structure was investigated by applying bending simulation and deformation tests. RSSI changes of the structure were examined by dropping distilled water, salt water and artificial urine solutions to simulate urinary incontinence. In addition, the maximum reliable reading range was determined by changing the distances between the RFID sensor and the reader antenna. In summary, all three articles presented within the scope of the thesis contribute to the literature separately. The articles reveal that the thesis topic and the results obtained as a result of the studies are original and innovative. The fact that the thesis topic is up-to-date and coupled with its relevance to personal health monitoring makes the results of the study important for everyone. The outcomes delineated in the articles and the devised sensors carry profound significance in addressing the contemporary issue of urinary incontinence-wetness detection. Moreover, it is anticipated that the findings of this thesis will serve as a guiding source for researchers in this field.
Development of ensete fiber based composites and their characterization

(Graduate School, 2021-09-07) Negawo, Tolera Aderia ; Kılıç, Ali ; 503152802 ; Textile Engineering

Composite materials are developed from two or more components having dissimilar properties to create the desired materials' physical, chemical, and mechanical properties. The main constituents of composite materials formulations include matrices, fibers, and additives or fillers. When composite matrices are from polymers, it is considered polymer composite. Fibrous materials from different sources classified as synthetic and natural fibers are used to reinforce the polymeric matrices. The composites from renewable raw material sources either bio-based polymers or natural fibers have been given attention by recent research works. Due to increasing environmental awareness and concern about sustainability, the academic and industrial sectors have started to focus on greener technologies, a major part of which is played by material development. This thesis aims to develop ensete fiber-based composite materials by characterizing their properties. Ensete fiber is extracted by decortication of pseudostem and leaf parts of the Ensete plant as a by-product. Ensete plant known as ensete ventricosum (scientific name) is a perennial plant that has leaves, a large underground corm, pseudostem, and one of the main food plants grown for traditional diet in East Africa especially in Ethiopia. Besides its abundance, Ensete fiber has a tensile strength of 513 MPa, fracture strain of 3.2%, fineness of 8-16tex, crystallinity index of 64.9%, and moisture content of 12.2%. Ensete fiber chemical composition is from 56% of cellulose, 24% of hemicellulose, 2.2% of lignin, and 17.8 % of other extractives, wax, and ashes. These properties of ensete fiber indicate its competitive candidate to make natural fiber-based biocomposites. The novelty of this research contributed to academic literature through its first extensive work on the effects of ensete fiber surface modification and grafting of compatibilizers to polymers on developed composites properties. Additionally, the effects of hybridization and stacking sequences on composite structures and properties; the extraction of micro cellulose crystals from ensete fibers were investigated. The nanocomposite developed from nano cellulose fibrils filled thermoset resin was also characterized for its thermal stability improvements and dynamic mechanical properties. The outcomes of this study have been given in the form of research articles published in high-impact factor journals such as Composite Structures and Composite Science and Technology. The methodology used to develop ensete fiber-based composites includes manufacturing techniques such as vacuum-assisted resin transfer moulding (VARTM), carding of fiber webs, twin-screw melt compounding and granulating, hot press moulding, and liquid cast moulding of composites. The design of experiments was prepared for each research article to address specific objectives and to contribute to the purpose of the thesis in general. Surface modification of ensete fiber by varying alkali concentration was investigated for its effects on the fiber properties and ensete fiber-based unsaturated polyester (UP) composite physical, mechanical, dynamic mechanical, and morphological properties. Mechanical test results revealed that 5.0 wt% alkali treated Ensete fibers and unsaturated polyester composites showed 14.5% and 43.5% increase in flexural strength and Young's modulus respectively when compared with untreated fiber composite. A positive shift in glass transition temperature (Tg) of composites after alkali treatment and tensile fracture surface morphology and roughness of ensete fiber SEM images indicates better interfacial interaction in treated ensete fibers and UP composites. The hybrid composites developed from carded ensete fiber webs and woven glass fiber fabrics reinforcing unsaturated polyester were characterized for the effects of stacking sequences. A hybrid composite GGEE and GEEG showed improvement in tensile properties when compared to polyester composites from pure ensete fiber in its carded web form. The composites stacked as glass-ensete-glass (GEEG) showed higher storage modulus as compared to glass-ensete (GGEE) composites whereas the loss modulus of the composites reinforced with glass fiber exhibited the maximum value of 407 MPa and the height of the damping curve decreased in the GEEG composite. As observed from fracture surfaces, a more extensive fiber pullout was observed for the GEEG sample compared to the only ensete fiber composite sample. Tg of composites was increased for ensete-glass hybrid composites which might be related to more restrictions and a higher degree of reinforcements in hybrid composites. The ensete/glass fiber hybrid polyester composites can be used as load-bearing structures and components where high resistance to deformations and thermal stability is necessary. Ensete fiber and high-density polyethylene (HDPE) composites were developed in the presence of maleic anhydride grafted polyethylene (Ma-g-PE) as a compatibilizer. The grafting process was done by optimized maleic anhydride concentration of 1.5% by weight fraction and 0.5% of reaction initiator called dicumyl peroxide (DCP) and the rest 98% of HDPE polymer. The formulated and premixed composite constituents (chopped ensete fiber, MA-g-PE, and HDPE) were melt compounded by twin-screw extrusion, granulated, and then composite plates were molded using a hot press machine. Increasing the ensete fiber loading from 15 wt.% to 30 wt.% has resulted in the composites being stiffer and harder leading to a decrease in elongation at the break of the composites. The physical properties such as density and water absorption % increased with fiber loading increments while melt flow index reduced. The addition of 5wt% compatibilizer into 25wt% ensete fiber-filled HDPE improved the fiber-matrix adhesion. Its tensile strength, flexural strength, and impact absorption energy increased by nearly 43%, 46%, and 56% respectively when compared to composites with the same fiber loading and without compatibilizer. Morphological analysis on micrograph images taken by SEM confirmed the failure mechanism of the composites. The results of the study show that ensete fiber-HDPE composite could be commercialized in the industry for construction and building, low-density furniture, and moldable structures in need of design flexibility. The micro or nanometer cellulose fillers extracted from green material sources such as ensete fiber are needed to be utilized to develop biocomposites. The study focused on the extraction of micro cellulose crystals from lignocellulosic ensete fiber and additions of nano cellulose fibrils to epoxy resin were investigated. The process of isolating micro cellulose includes chemical and mechanical methods. Lignin and hemicellulose of ensete fibers were removed by soaking chopped short fibers in an alkali solution (17.5 wt% NaOH concentration) for 4 hr. at room temperature. The alkali treated fibers were washed with deionized water several times to keep PH value at 7; filtered to remove lignin and hemicellulose, and dried at 80 ℃ for 24 hr. Acid hydrolysis by 1M hydrochloric acid was done at 80 ± 5 ℃ for 2 hr. to remove hemicelluloses, pectin, and some of the suspended cellulose amorphous, and then fibrils of cellulose were mechanically ball milled to micro cellulose crystals. The analysis from FTIR measurements, x-ray diffraction, optic microscope, and SEM images revealed the removal of lignin, hemicelluloses, pectin, wax, and also hydrolysis of amorphous cellulose parts during the chemical process. The diameters of extracted MCC were ranging from 1-10µm. The epoxy resin filled with varying weight fractions of cellulose nanofibrils was moulded and cured by liquid cast moulding techniques. The effects of incorporating nano cellulose fibrils filler into epoxy at different loading (1wt%, 3wt%, and 5wt%) were investigated. The results of thermal properties from DSC, TGA, and DMA discussed thermal stability and stiffness of epoxy nanocomposites. From DMA test results, the reduction in tan delta peak height of nanocomposites with the increase in NCF loading shows increments of stiffness imparted by fillers. The glass transition temperature of nanocomposites shifted to a higher temperature as the filler loading and uniform dispersion were attained. The thermal stability of CNF filled nanocomposites can be compared from TGA results. The temperature where maximum weight loss happened is shifted to a higher temperature when compared with pure epoxy polymer. CNF fillers acted as a thermal insulating barrier to the epoxy polymer and resulted in less thermal degradation of nanocomposites relatively. From overall test results, 3wt% CNF is the optimized cellulose nanofibrils filler loading for better thermal properties and modulus of the epoxy-based nanocomposites. In conclusion, based on currently available technologies the utilization of an ensete fiber which is from renewable sources to be used as reinforcements of polymeric matrices and alternative new green composite products were able to be developed for desired engineering applications as recommended in each specific study done.
Development of stretchable conductive fabric through different metals coating approach for e-textile applications

(Graduate School, 2022-07-25) Hassan, Zuhaib ; Kalaoğlu, Fatma ; 503122807 ; Textile Engineering

This study aims to manufacture and characterize various types of conductive (cotton knitted and polyester knitted) fabrics. The fabrics were prepared through the electro-less copper metal coating approach. The effect of copper electroleess plating on different types of fabric structures and on different crossections of yarns was also observed. The main response of prepared fabric was electrical conductivity, EMI shielding and their durability against washing and rubbing. The current research activity has multiple benefits considering extensive comparison with other studies. Previously electroless plating has been performed by different salts and reducing agents' combinations over different fibres. However, there were no study available to metallize the fabric structures having different GSM and different cross section of fibres. Secondly, we have also studied the effect of different fibrous cross-section (round, hollow round, W shape and octolobel) against copper electroless plating. At first, nine-combed cotton knitted fabric samples with different yarn fineness and elastane percentage were selected in order to see effect of these parameters on electrical conductivity and physical properties of samples such as an increase in weight and thickness, impact of washing cycles and abrasion resistance on the electrical conductivity of the fabric sample. The surface morphology of all the knitted cotton fabric samples were also explored before and after the coating method via scanning electron microscope (SEM) and it showed a remarkably uniform deposition of copper on the fabric surface. the energy dispersive spectroscopy (SEM-EDX) was performed to determine the coated material content on the surface of the fabric after the metal coating process. The utility of conductive fabrics was analyzed for electromagnetic shielding ability over frequency range of 30 MHz to 1.5 GHz. The electrical conductivity and amount of metal deposition was found to be higher for the fabric samples having less GSM and higher cotton percentages in their structures. The results revealed that knitted cotton fabric of 5% elastane with the finer yarn count (Ne=40/1) showed lowest resistivity (3.24 Ω.cm) as compared to the other knitted cotton fabric of 10% elastane with a finer count (Ne=40/1) or 5% elastane with coarser (Ne=30/1). The increase in elastane content into fabric structure also influences the fabric stretchability. The objectives of second part of the study were, to carry out research with the best performing three samples obtained from the first part of the study and three single jersey knitted cotton fabric samples were selected. The selected fabric samples with GSM (136, 154 and 176 GSM) out of nine fabric samples were used in this part. These fabric samples provided the lowest value of electrical resistivity coupled with high EMI shielding and more contents of metal particles. Thereafter, the selected samples were pre-treated with laser to enhance the surface roughness, then electroless plating was performed in order to see the impact of roughness on copper deposition. This section of the research work addresses the development and characterization of conductive cotton fabrics treated with lasers in context of copper (Cu) metallization methodologies. The abrasion resistance, thickness, and durability of the laser-treated knitted cotton fabric samples were investigated. Additionally, samples exhibited exceptionally consistent deposition of Cu nanoparticles on the surface of cotton fabric when the surface morphology of the laser-treated surfaces was examined by employing the scanning electron microscope (SEM) both before and after the coating procedure. To assess the elemental analysis on the surface of the treated samples following the electroless metallization process, an energy dispersing spectroscopy (SEM-EDX) examination was performed. This section of the study indicated that fabric samples that had been laser-treated outperformed untreated fabric samples in terms of wear resistance. Abrasion resistance being one of the significant features in electric textile applications, laser-treated samples might thereby be the best options. The third part of the study was the development and characterization of conductive textured and non-textured polyester fabrics with different cross-sections. The electroless copper plating method was selected to impart conductivity on fabric structures. The deposition of copper nanoparticles on textured and non-textured polyester fabrics was characterized by electrical conductivity, electron scanning microscopy (SEM), microscopic morphology, and energy dispersive X-ray spectroscopy (EDX). SEM images revealed a uniform copper nanoparticle coating of a thin film on textured and non-textured polyester fabrics. The properties of conductive textured polyester fabrics were compared in terms of electrical conductivity, wear resistance, thickness and durability with non-textured conductive polyester fabrics. Structural studies showed that the crystalline surface of the textured and non-textured polyester fabric structure is not affected by electroless metallization. Conductivity studies have shown that textured (lowest resistivity 2.18 Ω.cm) and non-textured (lowest resistivity 76.39 Ω.cm) polyester fabrics have good electrical conductivity. When the durability of conductive textured and non-textured polyester fabrics was examined against washing and rubbing fastness, the textured polyester fabrics showed good retention of copper nanoparticles by maintaining their electrical conductivity level after 250 abrasion cycles. Furthermore, resistivity analysis was also carried to study the effect of copper metallization and conductivity against different morphological structures of fibres. It was observed that there are lower values of electrical resistivity for each coated sample. The resistivity was found to be lowest for hollow round coated fibres (either textured or non-textured). The behaviour of metal deposition for hollow round fibers and electrical conductivity was further justified from the SEM analysis. The W shape fibers showed less amount of metal deposition and higher electrical resistivity values as compared to all. The final applications of developed copper plated fabrics are in the field of smart textiles, sensors, stretchable actuators, EMI shielded panels and stretchable electrodes. Keywords: Conductive textiles, Electroless plating, Copper coating, Electromagnetic interference shielding, sensors and actuators, Stretchable conductive fabrics, Smart textiles, metal coatings, textured polyester fabrics, Metal coated, Cross-sectional fiber.
Development of structural health monitoring system for fiber reinforced polymer composites

(Lisansüstü Eğitim Enstitüsü, 2021) Shahrukh, Shahbaz ; Berkalp, Ömer Berk ; 692349 ; Tekstil Mühendisliği

Fiber Reinforced Polymer (FRP) composites have emerged as a promising structural material for high-end applications. Their advantage of tailored properties according to specific requirements of desired applications has enabled them to achieve a preferred position above conventional metals. Glass Fiber Reinforced Polymer (GFRP) composites have gained a huge market in advanced engineering applications, among which aerospace and automotive industries are significant. The advancements in technologies have enabled the industries to commercialize large-scale composite architectures with higher productivities. Although composites have been offering reliable performance for large-scale and complex architectures, their maintenance is necessary for safety reasons and prolonging the service life with the least costs involved. The anisotropic nature of composites makes the detection of damage and failure very complicated in real-time. Therefore, various Structural Health Monitoring (SHM) techniques are being studied widely to monitor structural integrity in real-time. Focusing on this issue, piezoresistive strain sensors have been investigated in this study which has the potential to offer real-time information about structural integrity. The primary aim of this study is to sense induced strains and damages in the composite structures in real-time for which three major categories of strain sensors have been developed and analyzed. To support the simultaneous multichannel electrical signal acquisition, an Arduino microcontroller setup was developed to offer customized electrical measurements. The setup was successfully designed and implemented to record real-time electrical measurements from the embedded sensors in composite specimens. Carbon fiber based strain sensors were utilized to detect induced strains during tensile and flexural loadings by coupled electrical measurements. The experimental results showed that carbon fiber rovings were highly sensitive to low strains in composites during tensile and flexural loadings. The dual assembly of strain sensors revealed that the piezoresistive behavior of carbon fiber strain sensors is opposite for compressive strain and tensile strain during flexural loading. Temperature cycles from -10 oC to 80 oC influenced the resistance of carbon fibers up to 7.29%. Multi-Walled Carbon Nanotubes (MWCNTs) based strain sensors were developed and embedded in GFRP composites to analyze their piezoresistive behavior. Carboxy and amide functionalized MWCNTs were used to develop CNT-enabled E-Glass fiber strain sensors. FTIR spectroscopy confirmed the interactions between MWCNTs and glass fiber surfaces. The electromechanical test results indicated that MWCNT coated sensors in GFRP composites show promising piezoresistive sensing characteristics with good cyclic reproducibility that is significant for in-situ strain monitoring and damage detection. The experimental results showed that amide functionalized MWCNT sensors had higher strain sensitivity to flexural strains, whereas higher sensitivity to tensile loading was noticed with carboxy functionalized sensors. However, more linear piezoresistive behavior was found with amide functionalized sensors. A significant reproducible behavior with -8% relative resistance change was noticed as an electrical response to temperature cycles in the range of -10 oC to 80 oC. The development of carbon fiber thin films as strain sensors using a facile method was experimented. Thin films having conductive properties were developed in six different formulations with casting techniques to analyze their piezoresistive behavior for strain sensing in FRP composites. Higher concentrations of short carbon fibers encouraged higher conductivities in thin films. The electromechanical testing in a three-point bending configuration showed that the higher concentration of short carbon fibers influenced the sensitivity of sensors positively in the elastic region. Moreover, higher reproducibility during cyclic loading was also achieved with high concentrations of carbon fibers. Temperature cycles from -10 oC to 80 oC affected the resistance of the sensors with a negative temperature coefficient of resistance. Overall, the studied sensors had more sensitivity to tensile strains as compared to flexural strains. However, carbon fiber thin films showed the highest sensitivity to the induced flexural strains. Further work may improve the efficiency of sensing various types of damages using these sensors.
Development of textile based temperature sensor for wearable electronics

(Graduate School, 2021-09-30) Arman Kuzubaşoğlu, Burcu ; Kurşun Bahadır, Senem ; 503122802 ; Textile Engineering

Due to their compressibility, bendability, and compatibility with irregular and curvilinear surfaces, flexible and stretchable devices are attracting attention and have a wide range of applications. The increasing number of publications in this field demonstrates the growing popularity of flexible sensors. Flexible sensors provide mechanical robustness, biocompatibility, multifunctionality, and comfort when compared to conventional rigid sensors. For this reason, next-generation wearable technologies are expected to be driven by interest in flexible, stretchable, and soft devices. Textiles, in addition to their protective and aesthetic functions, provide an exceptional flexible platform for providing sensing functions and comfort to the wearer with diverse range of fibers, yarns, and fabric structures. New developments in printed electronics enable mass production of sensors using efficient printing processes by considerably minimizing costs and enhancing the potential of large-scale production. In this thesis, at first, the capabilities of temperature sensors, their sensing method, and previous research that has been conducted on them are presented. Additionally, the techniques and uses of inkjet printing are examined in detail. A comprehensive explanation of inkjet printing technology and printing challenges are issued. Dispersion is required for the development of inks that include carbon nanotubes. Due to the hydrophobic nature of carbon nanotubes, they must be distributed using a combination of mechanical and chemical methods. Numerous methods, including ultrasonication, non-covalent and covalent alterations, were used to disperse nanotubes. The use of various types of carbon nanotubes in CNT ink formulations is also studied. The development of conductive inks formulations containing CNT, PEDOT:PSS and CNT/PEDOT:PSS with a proper evaluation guideline is studied. Moreover, the concepts and properties of functional materials, as well as the critical additives used during the printing process that can have a significant influence on the printing process of conductive inks are discussed. The physical, structural, morphological, and electrical properties of the materials are investigated using various techniques (UV-Vis, FTIR, optical profilometer, SEM, AFM, optic microscope, multimeter, etc.). With relevant to print quality, the textile basis material should be dependable, maintaining a level surface and good uniformity during the printing process. In order to create conductive material sensors for temperature measurement, the inkjet printing process was used, which has the advantage of reducing ink waste while also being a low-cost and simple method. Following the procurement of CNT-based inkjet suitable dispersion, a PEDOT:PSS/CNT composite ink and a PEDOT:PSS inkjet appropriate dispersion are manufactured for temperature sensing. Appropriate ink formulations have been developed to produce high-quality inkjet-printed sensors, which are typically characterized by low imperfection points throughout the surface of the printing material. The sensor manufacturing process is then completed by including silver yarn, followed by the application of silver based conductive glue and an encapsulating operation. Spectrophotometer studies were conducted to determine the qualities of carbon nanotube printing when many print passes are used, as well as the color characteristics of the produced specimens. The properties of CNT based, PEDOT:PSS based and CNT/PEDOT:PSS composite based sensors are compared to investigate their temperature sensing performance. Hence, proper ink formulations with appropriate physical and chemical properties that typically affects homogeneous printing surface characteristics and sensing properties, were successfully developed by analysing their morphologies and printing parameters. It was determined whether the printed temperature sensors performed properly by subjecting them to a temperature range ranging from 25 to 50 degrees Celsius. Furthermore, wear and performance tests, such as durability against bending, folding, humidity, rubbing, washing, light, and human sweat, were carried out with the help of some characterization methodologies in order to investigate the sensor's reliability and durability under unfavorable situations. The sensor real time measurement using of a mannequin and human gloved hand are reported with discussions. As a result, during our proof-of-concept inquiry, our newly designed temperature sensor was placed to a mannequin's skin and human body on a gloved hand for temperature monitoring. Our developed wearable sensor provides highly accurate temperature monitoring. Lastly, the application based on artificial intelligence for the modeling of wearable sensors in various temperature and humidity conditions is described. Artificial neural networks (ANN) are used to model wearable sensors in various temperature and humidity conditions. The relationship between temperature, humidity, and electrical resistance is presented with the use of ANN. This innovative wearable temperature sensor development process is expected to aid development of smart wearable technologies. The developed sensor with its good mechanical properties and excellent sensing performance is believed to be useful for use in the textile products. Moreover, this developed sensor also offers the opportunity to be directly included in wearable smart systems in industrial production. In addition to the lack of standardized and consistent manufacturing techniques, there are unfortunately not yet any regular and comparable tests that can be used for the development and implementation of wearable e-textile sensors. Hence, this study will pave a way for development phases and implemenation of wearable e-textile sensors, in particular, contribute to industrialization in this area. To conclude, the developed textile-based sensor might be a solution instead of rigid device components for human body temperature monitoring and it can be directly utilized by sticking the sensor on various garment types while maintaining the user's comfort. Hence, it reveals a strong potential for use in wearable healthcare and biomedical applications.
Development of textile-based resistive pressure sensing socks in diabetes mellitus for early detection of DFU

(Graduate School, 2024-06-28) Tosun, Abdullah Ömer ; Atalay, Özgür ; 503211801 ; Textile Engineering

Today, millions of people suffer from diabetes that will last a lifetime. The energy necessary for people to continue their daily life activities is obtained from protein, carbonhydrates and fats. These basic nutrients need to be broken down into the smallest pieces in order to be absorbed. The most important of these nutrients are simple sugars called glucose. Cells contain glucose, which the human body needs, It makes it usable with the help of the hormone secreted by the organ called the pancreas. The name of this hormone is insulin. If this hormone does not work properly, the food taken cannot be used as energy. Diseases that occur as a result of a deficiency of the insulin hormone or not working properly are called diabetes. This disease can occur in people during childhood, or it can occur after the age of 20s and 25th depending on genetic reasons. The disease shows itself as Type 1 and Type 2 Diabetes. Since it is a disease that progresses in a very insidious and painless way, the disease may not be diagnosed for many years. Since Type 1 diabetes mostly occurs in childhood and youth, this disease is called juvenile diabetes in the literature. These patients have to take insulin hormone externally as a lifelong supplement. In our society, 10% of diabetes patients are Type 1. Type 1 diabetes is a disease that is included in the group of diseases called autoimmune diseases and continues throughout life. The immune system, which acts for an unknown reason, damages beta cells in the pancreas, which are responsible for insulin production. When this damage exceeds 80%, disease specifications emerge. The only rule in the treatment of type 1 diabetes patients is insulin therapy. In this type of diabetes, insulin injection is essential and plays a role in saving the patients' life. In addition to insulin injection, a healthy and regular diet, sports and education should be an invariable part of patients' life. In order to maintain these principles and personal care, they should pay maximum attention to these principles. It is essential for patients to keep blood sugar between acceptable levels, to prevent very serious complications such as hyperglycemia and hypoglycemia that may put the person's life at risk, and to provide and maintain ideal body weight and protein consumption, consumption of various foods, excess fiber in foods, consumption of simple sugars under the control of a dietitian and regular doctor appointments should not be interrupted. Exercise should be done regularly every day. In order for patients not to be exposed to advanced complications, they should first take all precautions for their own health. The other disease seen in diabetes patients is type 2 diabetes. Genetic and environmental factors play a role in type 2 diabetes patients. These patients have insulin resistance and insulin secretion abnormality. There are abnormalities in insulin secretion due to genetic factors. Inactivity and desk life trigger this disease as environmental factors. In addition, obesity, one of today's diseases, causes insulin resistance and as a result, diabetes is inevitable. As in Type 1 diabetes patients, Type 2 diabetes patients have to pay close attention to their nutrition, daily physical activity and blood sugar. The person should eat healthy and regularly, and avoid foods and drinks that will cause sudden rise and fall in blood sugar. The patient should also regularly measure blood sugar 6 times on an empty stomach and note the averages and not neglect the doctor's appointments. In both Type 1 and Type 2 diabetes diseases, diabetic coma, irreversible damage to vital organs, especially (silent and latent period of diabetes) and in cases where the patient does not receive adequate treatment or neglects the kidneys insidiously and without pain, in the more normal-high stages of diabetes. Bleeding due to intraocular vascular structure can lead the patient to blindness in a very short time. As a result of the deterioration of kidney functions, the patient may be sentenced to dialysis for life. Depending on the damage to the cardiovascular system, permanent damage may occur in the feet and hand limbs of the patients, and accordingly, these limbs must be cut off suddenly. Since the blood cannot go to all organs and limbs in the body in an equal and balanced way in diabetic patients, over time, excess pressure and numbness occur in areas with less blood flow, and accordingly the areas where numbness occurs should be surgically cut. The best example for this is the foot part of diabetic patients. Depending on the disease, the blood cannot reach every region equally on the soles and fingers of the foot and over time, numbness and pressure increasement occur in certain parts of the foot. If the person does not realize this situation in time the damaged tissue is removed by incision method in order to prevent the decay from progressing to other areas comes into play at this point. In the thesis study, it is aimed to carry out a study in order to make early diagnosis in diabetes patients by integrating switch mechanism that is pressure sensitive sensors under socks. The working principle of switch sensors is based on short-cut under pressure. The usage area of switch sensors is gradually expanding due to their advantages such as flexibility, accuracy of data, low energy use and sensor design. In terms of sustainability and ease, the use of switch sensors with parallel conductive layers seems more logical. In this thesis, 3 conductive layers were manufactured and they were separated with mesh fabrics. In the case of abnormal external pressure bottom conductive layers become active and short-cut occurs and in the case of lower external pressure top conductive layers touch each other and short-cut occurs. The data is transferred whereby conductive channels which is TPU coated in order to thwart short-cut during transmitting data from soft sensors to central unit. The resistive sensing mechanism has been adopted due to it is simple to manufacture and doesn't require any kind of dexterity or knowledge of making patterns. It is also overt that there will not be any defect which is derived from sock knitting machine and the budget to set up this system is pretty much lower when it is compared to sock knitting machines. When it is gathered up all these advantages, we can absurb that switch resistive sensing is also workable and effective approach in order to predict DFU before any possible amputation.
Electrospun composite nanofibers with metal/metal oxidenanoparticles

(Graduate School, 2021-04-21) Başkan, Havva ; Karakaş, Hale ; 503142809 ; Textile Engineering ; Tekstil Mühendisliği

Functional materials have taken great interest due to their superior physical and chemical features which allow them to be succesfully used in a wide range of engineering applications. Nanomaterials, specifically nanofibers are regarded as functional materials due the their high surface area to volume ratio, high pore interconnectivity, small pore dimensions and superior chemical and mechanical features. Nanofibers are produced by mainly electrospinning which is a simple and inexpensive technique. Moreover, many types of polymers or polymer blends can be converted to nanofibers by electrospinning. Combination of two or more materials in a nanofibrous structure can result in functional materials. In this thesis, the goal was obtaining functional nanofibrous materials by incorporating a noble metal (silver) and metal oxides (iron III oxide (Fe3O4) and aluminum oxide (Al2O3)) in novel polymeric nanofiber structures and evaluate the biological features of the samples for medical applications. First of all, a novel Poly (acrylonitrile-co-itaconic acid) (P (AN-co-IA)) copolymer was synthesized by emulsion polymerization. In the literature, copolymerization of itaconic acid (IA) with acrylonitrile (AN) was performed for decreasing the cyclization temperature of polyacrylonitrile (PAN) homopolymer and consuming less energy for carbon fiber production. However, in the scope of the thesis, it was aimed to enhance the application areas of IA by integration of metals and metal oxides. Since Fe3O4 nanoparticles and Al2O3 nanoparticles play an imperative role in many biomedical applications, they were utilized together with P (AN-co-IA) copolymer. It was very difficult to study with metal oxide nanoparticles due to their tendency to agglomeration. For that reason, the appropriate amount of metal oxide nanoparticles was determined first by using polyacrylonitrile /N,N Dimethylformamide (PAN/DMF) solutions. Afterwards, the optimized amout of Fe3O4/ Al2O3 nanoparticles were added into P (AN-co-IA)/DMF polymer solutions and the solutions were subjected to electrospinning to obtain a nanofibrous structure. In addition to conventional electrospinning, coaxial electrospinning was also performed for metal oxide nanoparticle incorporation. Detailed morphologic and spectroscopic characterizations of the obtained nanofibers were performed. Thermal features of the resultant nanofibers were also analyzed by Differential Scanning Calorimety (DSC) and Thermogravimetric Analysis (TGA). It was captured from the characterization results that addition of metal oxide nanoparticles to P (AN-co-IA) copolymer structure altered the features of the plain P (AN-co-IA) nanofibers. Even using very small amount (1 wt %) of Al2O3 caused improvements in thermal stability of the nanofibers. On the other side, silver nanoparticles (AgNPs) formation and integration to polymer structures were achieved by different chemical and physical methods. By the assistance of P (AN-co-IA) polymer and DMF, AgNPs were formed in-situ in polymer solution and then the polymer solution was electrospun for nanofiber production. The novelty of the method was related to the decreased reduction duration of silver nitrate (AgNO3) by using P (AN-co-IA) polymer. The method was compared with the literature studies on the utilization of PAN polymer for reduction of AgNO3. P (ANco-IA) polymer allowed to obtain AgNPs from the precursor AgNO3 two times faster than PAN. Moreover, it was understood that P(AN-co-IA)/Ag nanofibers had high electrical conductivity, enhanced thermal stability and satisfying nanofiber morphologies. Besides conventional electrospinning, AgNPs were introduced into P(AN-co-IA) polymer structure via coaxial electrospinning. In the process, AgNO3/DMF solution was prepared to be used as a shell solution and P (AN-co- IA)/DMF solution was prepared as a core solution. Since the most important point in coaxial electrospinning is the feed-rate of core and shell solutions, a set of experimental study was performed for the optimization of flow-rate (0.2 ml/h) of shell solution. After coaxial electrospinning, P(AN-co-IA)(core)/ AgNO3 (shell) nanofibers were subjected to UV-irradiation to generate AgNPs by the reduction of AgNO3. UVirradiation duration was optimized as 3 hours by using PAN(core)/ AgNO3 (shell) nanofibers. In addition to P (AN-co-IA) and PAN polymers, biodegradable and biocompatible poly (3-hydroxybutyrate) P (3HB) and poly (3-hydroxyoctanoate-3 hydroxydecanoate)(P (3HO-3HD)) polymers were also utilized for the combination of AgNPs. To this end, nanofibers of P (3HB)/P (3HO-3HD) were collected via conventional electrospinning and by dip-coating they were coated with AgNPs. As in the nanofibers including metal oxide nanoparticles, detailed morphologic, spectroscopic and thermal characterizations of the resultant nanofibers were performed by Scanning Electron Microscope –Energy Dispersive Spectroscopy (SEM-EDS), Ultra Violet-Visible (UV-Visible) and Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy, and DSC. Most importantly, antimicrobial activity studies of P(AN-co-IA)/Ag nanofibers (obtained via conventional electrospinning) against S. aureus, E.coli, P. aeruginosa and C. albicans and immunomodulatory properties of P (3HB)/P (3HO-HD)/Ag nanofibers against special cytokines (IL-1 (α and β), IL-6, IL-8, TNF-α, TGF-β and HBD-2) were evaluated. Related to the antimicrobial activity results of P (AN-co-IA)/Ag nanofibers, it was observed that the nanofibers produced inhibition zones against the studied microorganisms. That was also proved by susceptibility testing. According to time-kill analysis, without silver nanoparticles, either PAN or P (AN-co-IA) nanofibers did not show any antimicrobial activity against any microorganisms. However, bacteriostatic/fungistatic activity was observed for all nanofiber samples which include AgNPs at almost all time points. Bactericidal activity was started from 24-48 hours and lasted until 120 hours at 10x Minimum Inhibitory Concentration (MIC) whereas fungicidal activity was observed between 120 and 168 hours at 10xMIC. Based on the real-time reverse transcriptase polymer chain reaction (RT-PCR) tests of P (3HB)/P (3HO-3HD)/Ag nanofibers, it was understood that while plain P(3HB)/P(3HO-3HD) nanofibers did not show any difference in the basal production of these molecules by HaCaT cells in culture, AgNP-containing P(3HB)/P(3HO-3HD) nanofibers upregulated the studied proinflammatory cytokines which were IL-1(α and β), IL-6 and IL-8 after 6 hours to start the healing process. Those findings of AgNPs containing P (AN-co-IA) and P (3HB)/P (3HO-3HD) nanofibers revealed that they could be used in wound dressing or tissue engineering applications effectively. Polypyrrole (PPy) is popular with its conductivity, but it can also be used in biological applications such as biosensors and drug delivery. However, due to the problems in processing with PPy, it is very difficult to obtain PPy nanofibers. In this thesis, it wasaimed to combine PPy with AgNPs to be used in biological applications and also converting it to a nanofibrous web structure by the help of P (AN-co-IA). Since it was difficult to electrospin P (AN-co-IA), PPy and AgNPs in a single step, AgPPy was synthesized via chemical oxidation polymerization first. Then AgPPy and P (AN-co-IA) was gathered in a nanofiber structure via coaxial electrospinning. AgPPy/DMF solution was prepared as shell solution and P (AN-co-IA) /DMF was prepared as core solution. It can be fairly said that the same protocol of the abovementioned coaxial electrospinning was performed for coaxial electrospinning of P (AN-co-IA) (core)/AgPPy (shell) nanofibers. Bead-free and continuous nanofiber morphologies with fine nanofiber diameters could be obtained. As a conclusion, in the scope of this thesis, functional nanofibers were achieved by incorporating metal/metal oxide nanoparticles into polymeric nanofiber structures with various experimental procedures. The obtained nanofibers are good candidates for medical applications where conductivity and antimicrobial activity are desired.
Elektro üfleme yöntemiyle üretilen poliviniliden florür (PVDF) nanoliflerin elektrostatik filtreleme özelliklerinin iyileştirilmesi

(Lisansüstü Eğitim Enstitüsü, 2022-05-18) Sağırlı, Merve Nur ; Kılıç, Ali ; 503191802 ; Tekstil Mühendisliği

Hava kirliliği, endüstrinin gelişmesiyle insan sağlığını tehdit eden bir unsur haline gelmiştir. Çeşitli boyutlardaki kirleticiler, gerek iç mekanda gerekse dış mekanda insanların solunum sistemine nüfuz ederek ölümcül sonuçlar doğurabilmektedir. Bu tehdidi ortadan kaldırmak amacıyla çeşitli hava filtreleme malzemeleri geliştirilmiştir. Geliştirilen malzemeler arasında, lifli matlar, kolay işlenebilirlikleri ve sahip oldukları gözenek özellikleri nedeniyle öncelikli tercih edilen malzemeler olmuştur. Lifli matlardaki lif çapının düşürülmesiyle, parçacıkların tutunması için daha yüksek yüzey alanı oluşturulmuş ve gözenekliliği kontrol edilebilen yapılar elde edilmiş olmaktadır. Ayrıca mat yüzeyindeki ve içerisindeki akış rejimi hesaba katıldığında, düşük çaplı liflerden meydana gelen malzemelerin oluşturduğu kayma akışı rejimi, filtre performansında pek çok açıdan avantajlı olarak yorumlanmıştır. Lifli hava filtrelerinde çeşitli parçacık yakalama mekanizmaları tanımlanmıştır. Bu mekanizmalar, parçacıkların hava akış rejimine göre hareketi esnasında bir akış düzensizliğine uğrayarak lif yüzeyine tutunmasını temel almaktadır. Parçacığın tutunması Brownian hareketi nedeniyle olduğunda Brownian difüzyonu, eylemsizlik nedeniyle olduğunda atalet çarpması ve kendi büyüklüğünden dolayı gözeneklerden geçemeyerek lif yüzeyine yakalanması nedeniyle olduğunda ise engelleme mekanizması olarak tanımlanmaktadır. Tanımlanan bu mekanizmalar, mekanik filtreleme olarak adlandırılmıştır. Gerek parçacığın gerek lifli yapının gerekse her ikisinin de elektriksel yüklendiği durumlarda elektrostatik yakalama mekanizması da bulunmaktadır. Bu mekanizmada, parçacıklar akış rejiminin etkisinden ziyade elektrostatik çekim nedeniyle lif yüzeyine tutunmaktadır. Lif çaplarının 0 – 100 nm (bazı tanımlarda 0 – 1 μm) arasında olduğu matlar nanolifli matlar olarak tanımlanmıştır. Polimer çözeltilerinden nanoliflerin elde edilmesi için de çeşitli yöntemler geliştirilmiştir. Bu yöntemler, çözelti yüzey geriliminin aşılarak bir lif çekim jeti oluşturmaya dayalı olarak tasarlanmıştır. Yüzey geriliminin aşılması için ise değişik yürütücü kuvvetler uygulanmış ve üretim yöntemi bu kuvvete göre isim almıştır. Yaygın kullanılan yöntemler arasında, yürütücü kuvvetin elektriksel alan kuvvetleri olduğu elektro-üretim, merkezkaç kuvvetlerden yararlanılan santrifüjlü üretim, basınçlı havanın kullanıldığı çözeltiden üfleme ve basınçlı hava ile elektriksel alan kuvvetlerinin eş zamanlı olarak uygulandığı elektro üfleme yöntemleri yer almaktadır. Nanolifli matların filtre performansı, hem parçacık yakalama yüzdesi hem de malzemenin girişi ve çıkışı arasındaki basınç farkı ile ölçülmektedir. Bir filtrenin, parçacık yakalama yüzdesinin mümkün olduğunca fazla olması beklenirken basınç farkının da olabildiğince düşük olması beklenir. Basınç farkının yüksek olması, havalandırma sistemlerinde kullanılan filtrenin enerji tüketimini artırmasına neden olmaktadır. Yukarıda anlatılan mekanik filtreleme mekanizmalarında, performansı yükseltmek için atılan adımlar, basınç farkının da yükselmesine yol açarken elektrostatik mekanizma söz konusu olduğunda yüksek performans gösteren daha düşük basınç farkına sahip malzemeler elde edilebilmektedir. Elektrostatik mekanizmanın etkin olduğu filtrelere elektret filtre adı verilmektedir. Bu filtrelerde lifli matlara elektriksel yük kazandırılmaktadır. Bunun için çeşitli yöntemler geliştirilmiştir. Söz konusu yöntemler, matın üretimi esnasında bir elektrik alan uygulamasına dayalı olabileceği gibi üretilmiş bir matın sonradan yüklenmesini de temel alabilmektedir. Bu tez çalışmasında, nanolifli elektret filtre üretimi hedeflenmiş ve matın üretimi esnasında ve üretim sonrasında uygulanan elektrostatik yüklemenin filtre performansına olan etkisi incelenmiştir. Bu tez çalışmasında, ham madde olarak gerek kimyasal gerekse fiziksel yapısından dolayı pek çok avantajlı özellikleri bulunan poliviniliden florür (PVDF) polimeri kullanılmıştır. Çözücü olarak dimetil formamid (DMF) ve aseton tercih edilmiştir. Üretim yöntemi ise çözeltiden üfleme ve elektro üfleme olarak belirlenmiştir. Çözeltiden üfleme yöntemi ile nanolifli matın üretimi gerçekleştirilmiş ve ardından üretilen mat korona deşarj yöntemi ile elektriksel olarak yüklenmiştir. Aynı çözelti kullanılarak elektro üfleme yöntemiyle de nanolif üretimi gerçekleştirilmiş ve bu iki matın filtre performansı kıyaslanmıştır. Çözeltiden üfleme ile elde edilen matın verimi %55, basınç farkı ise 43 Pa olmuştur. Korona uygulaması ile basınç farkı değişmezken filtre verimi %10'dan fazla artarak %68'e ulaşmıştır. Elektro üfleme ile elde edilen matta ise %97 verime ulaşılmıştır. Ancak bu yöntemde basınç farkı da yükselmiş ve 175 Pa olarak elde edilmiştir. Matların sahip olduğu filtre performansının ne kadarının elektrostatik, ne kadarının mekanik etkiden kaynaklandığını gözlemlemek amacıyla izopropil alkol (İPA) ile nötrleme işlemi yapılmış ve nötr hali test edilmiştir. Ayrıca matların bu performansı muhafaza etme özelliklerinin değerlendirilmesi için belirli sürelerde tekrarlı ölçümler (gün 1, gün 3, gün 7, gün 17) gerçekleştirilmiştir. İPA uygulaması sonrasında, herhangi bir yükleme işlemi yapılmamış olan nanolifli matın filtre verimliliği ve basınç farkı sırasıyla %41 ve 43 Pa iken korona uygulanmış olan matta %45 verimlilik ve 45 Pa basınç farkı ölçülmüş, elektro üfleme ile elde edilen matta ise verimlilik %85, basınç farkı ise 160 Pa olarak kaydedilmiştir. Bu durumda, çözeltiden üfleme ile elde edilen matta, verimliliğin yaklaşık %10'unun elektrostatik yakalama mekanizmasından kaynaklı olabileceği yorumu yapılabilmektedir. Elektro üflemede de, elektrostatik yakalama mekanizması, filtre verimliliğinin yaklaşık %10'unu kapsamaktadır. Öte yandan, korona ile yüklenmiş olan matta, elektrostatik yüklemenin sağladığı verimlilik yaklaşık %20 olmuştur. Tekrarlı ölçümlerde ise 17 günün sonunda çözeltiden üfleme ile üretilmiş matın verimliliği %2, korona yüklemesi yapılmış olan matın verimliliği %8 ve elektro üfleme ile elde edilmiş matın verimliliği %15 azalmıştır. Böylece elektro üfleme ile üretilen matın verimliliğinin zamanla azalma hızının diğerlerine kıyasla daha yüksek olduğu sonucu çıkarılmaktadır.
Ev tipi yıkamalarda suyun tekrar kullanımı için yıkama atık suyundan renk giderme sisteminin geliştirilmesi

(Lisansüstü Eğitim Enstitüsü, 2021-11-23) İlkiz Arslan, Başak ; İridağ Beceren, Yeşim ; Candan, Cevza ; 503062802 ; Tekstil Mühendisliği

Son yıllarda temiz su kaynaklarının hızla kirlenmesi nedeniyle su geri kazanımının önemi günden güne daha da artmaktadır. Bu tez çalışması öncelikle su kaynaklarının sürdürülebilir olmasını desteklemek ve kullanılan atık suyu tekrar kullanabilmek amacıyla tetiklenmiştir. Pazarda yaygın bulunan yüksek kapasiteli ve önden yüklemeli ev tipi çamaşır makinelerinde her çevrimde yıkama ve durulama adımlarının tamamında minimum 50 L ve üzerinde su tüketimi gerçekleşmektedir. Sunulan tez çalışmasında, ozonlama yöntemi kullanılarak renkli çamaşırların yıkanmasıyla ortaya çıkan çamaşır makinesi atık sularındaki rengin giderilmesi ve rengi giderilen suyun bir sonraki yıkamada tekrar kullanılması hedeflenmiştir. Bu hedef doğrultusunda, çamaşır makinesi atık suyundaki boyarmadde konsantrasyonunu tahminleme, ozon ile renk giderme sistemine sahip makine prototipinin hazırlanması çalışmaları ve bu makinede renk giderme testleri yürütülmüştür. Çamaşır yıkama sonucunda oluşan atık su, gri su kategorisindedir, hanelerde evsel aktiviteler için kullanılan toplam su içerisinde yüksek bir paya sahip olup (%27) geri kazanım ve tekrar kullanım için potansiyel oluşturmaktadır. Günümüzde yaygın olarak tercih edilen pamuk içerikli tekstil ürünleri çamaşır makinelerinde sıklıkla yıkanmakta olup, bu ürünlerin renklendirilmesinde çoğunlukla reaktif boyarmaddeler kullanılmaktadır. Bu reaktif boyarmaddeler içerisinden azo ve antrakinon boyarmaddeler yaygınlık, suda yüksek çözünürlük göstermeleri, life fikse oranlarının düşük olması ve atık suda risk oluşturmaları nedeniyle tercih edilmiştir. Yıkamaya karşı renk haslığı düşük ve lekeleme konusunda problemli olarak bilinen kırmızı ve mavi renkler belirlenerek, bu renklerin elde edilmesi için azo boyarmadde sınıfından reaktif kırmızı 195 ve antrakinon boyarmadde sınıfından reaktif mavi 19 boyarmaddeleri seçilmiştir. Çalışmada yaygın kullanılan ve sık yıkama ihtiyacı bulunan örme kumaşlar tercih edilmiş ve ticari koşullarda üretilip boyanmıştır. Tekstil atık sularında organik kirleticilerin fazla bulunmasından dolayı, bu sulardan reaktif boyarmaddelerin giderilmesinde oksidasyon yöntemlerinden ozonlamanın ve ozon ile diğer yöntemlerin kombinasyonlarının sıklıkla tercih edildiği belirlenmiştir. Teknolojisinin olgunlaşmış olması, yan ürün açığa çıkarmaması, yerinde renk giderimini hızlı şekilde gerçekleştirebilmesinden dolayı çamaşır makinesi için ozonlama yöntemi tercih edilmiştir. Çamaşır makinesinde renk giderimi için yıkama çevrimindeki uygun yıkama adımının -hedef atık su çözeltisinin- belirlenmesi için yapılan deneysel çalışmada, yapılan ölçümlerde deterjan konsantrasyonu düşük olan ve yumuşatıcı içermeyen birinci durulama adımının renk giderim için daha uygun olduğuna karar verilmiştir. Literatür araştırması sırasında renk giderimi çalışmalarında çoğunlukla konsantrasyonu bilinen yapay çözeltiler ile çalışıldığı saptanmıştır. Oysa, çamaşır makinesinde yapılan yıkamalar sonunda ortaya çıkan atık suların içeriği farklı (lif, hav, deterjan vb.) ve oldukça kaotiktir. Literatürde rastlanmaması nedeniyle tezin yenilikçi yönü olarak yapay çözeltiler yerine "evsel çamaşır makinesi atık suları" ile çalışılmıştır. Ev tipi çamaşır makinesinden kaynaklı boyarmadde içeren atık suyun renginin giderilmesi için ozonlama ile renk giderme sistemi önerisi yapılmıştır. Yaşanan en büyük zorluk, yıkama sırasında boyalı kumaşlardan elde edilen atık suların boyarmadde konsantrasyonunun bilinememesidir. Bu atık suların boyarmadde konsantrasyonunun tahmin edilmesi için iteratif bir yaklaşım geliştirilmiştir. Boyarmadde konsantrasyonunun belirlenebilmesi için VIS spektrofotometre cihazı ile renkli atık su çözeltilerinin absorbans taraması yapılmış ve spektrumda maksimum absorbans değerini veren dalgaboyu tespit edilmiştir. Ancak, çamaşır makinesi atık suyunda yapılan ölçümlerde maksimum absorbans değeri elde edilememiştir. Boyarmadde konsantrasyonunun tahmin edilebilmesi için geliştirilen yaklaşımda, birinci adımda, saf su ile yapay olarak hazırlanan kontrol boya çözeltilerinin spektrum taramalarından maksimum absorbans değerlerinin elde edildiği dalgaboyları Reaktoset Red RFT (C.I. RR 195) için 540 nm, Reaktoset BRL Blue R Spec (C.I. RB 19) için 592 nm olarak belirlenmiştir. İkinci adımda, boya konsantrasyonları ve deterjan konsantrasyonları, sırasıyla, ana yıkama adımı için 10 –– 100 mg/L aralığında ve 4,6 g/L olarak; durulama adımı için 1 – 40 mg/L aralığında ve 0,5 g/L olarak hazırlanmış ve çözeltilerin absorbans ölçümlerinden kırmızı (RR 195) ve mavi (RB 19) boyalar için ana yıkama ve durulama kalibrasyon eğrisi denklemleri elde edilmiştir. Üçüncü adımda, renkli atık su çözeltileri tergotometer cihazında boyalı kumaşların yıkanması sonucunda elde edilmiştir. Bu çözeltiler ilgili dalgaboyunda net bir absorbans değeri vermediğinden, boyarmadde konsantrasyonunun hesaplanması için adım 2'de elde edilen kalibrasyon eğrilerine ait denklemlerin (kırmızı atık su için: A=0,0186C+0,0427, R² = 0,9997; mavi atık su için: A=0,0115C+0,0540, R² = 0,9966) kullanılmasına karar verilmiştir. Doğrulama testlerinde, denklemlerden hesaplanan boya konsantrasyonuna en yakın konsantrasyondaki deterjanlı yapay boya çözeltilerinin spektrumları ile renkli kumaşlardan elde edilen spektrumların karakteri farklı olmasına rağmen belirlenen dalgaboyunda üst üste çakıştığı saptanmıştır. Çamaşır makinesi ve tergotometer cihazından elde edilen atık su çözeltilerinin absorbans ve konsantrasyon değerleri arasında güçlü bir ilişki olduğu belirlenmiş ve tergotometer cihazının su ve kumaş sarfiyatını azaltmak amacıyla çamaşır makinesi yerine kullanılabileceği kanaatine varılmıştır. Renk giderme sistemine sahip makine prototipi için, bir ozon düzeneği kurularak çalışmalara başlanmıştır. Kurulan düzenekte hava kompresörü, hava kurutucu, akış ölçer, ozon jeneratörü, ventüri, su haznesi, iki adet su pompası ve debimetre yer almaktadır. Ozon düzeneğinde yapılan deney tasarımı sonucunda renk giderme etkinliği üzerinde en etkili faktörlerin sırasıyla %22,0 ile boyarmadde*ozon jeneratörü ikili etkileşimi, %15,4 ile ozon jeneratörü*ozonlama süresi ikili etkileşimi ve %14,8 ile tek başına ozon jeneratörü olduğu saptanmıştır. 500 mg/sa kapasiteli (500-B kodlu) ozon jeneratörü ile en yüksek renk giderme oranlarına ulaşıldığından bu ozon jeneratörünün kullanılmasına karar verilmiştir. Ventüri sistemi ve geri kazanılan suyun bulunacağı depoya sahip 9 kg kapasiteli çamaşır makinesi prototipi hazırlanmıştır. Sistemin çalışma prensibi şu şekildedir: Dışarıdan hava kompresörü yardımıyla çekilen ortam havası ozon jeneratöründen geçirilerek ozon üretilmekte ve ventüri elemanına taşınmaktadır. Pompalar yardımıyla ventüri elemanında renkli su ve ozon buluşmakta, belirli süre yapılan sirkülasyon sonrasında ozonlama yoluyla renksiz su elde edilmektedir. Önerilen denklemler kullanılarak boya konsantrasyonları hesaplandığında, renkli kumaşların farklı tüketici koşullarında yıkanması sonucu atık su boya konsantrasyonunun 15 mg/L ile 90 mg/L arasında değişkenlik gösterdiği saptanmıştır. Çamaşır makinesinde ozonlama testleri iki aşamada yürütülmüştür. Birinci aşamada, çamaşır makinesinde 14 L olarak deterjanlı, 20 – 40 – 60 – 80 mg/L boya konsantrasyonuna sahip yapay çözeltiler hazırlanmış ve ozonlanmıştır. İkinci aşamada, gerçek yıkama koşulunu temsilen ticari koşullarda üretilen kumaşların (1 kg) Beko 9 kg çamaşır makinesinde pamuklu 40 programında 52 g standart deterjan ile yıkanmasından elde edilen birinci durulama suları toplanarak ozonlanmıştır. Kırmızı ve mavi yapay boya çözeltilerinde renk giderme oranı %95 ve üzerinde gerçekleşmiştir, görsel olarak rengin tamamen giderildiği tespit edilmiştir. Renk giderimi etkinliğinin başlangıç boya konsantrasyonuna ve boyarmadde tipine bağlı olduğu belirlenmiştir. Boya konsantrasyonu arttıkça renk giderimi daha uzun sürede gerçekleşmiştir. Reaktif kırmızı 195 boyarmaddesi ile hazırlanan çözeltilerde renk gideriminin reaktif mavi boyarmadde ile hazırlanan çözeltilere göre daha uzun sürdüğü belirlenmiştir. Kırmızı ve mavi kumaşlardan elde edilen birinci durulamaya ait atık suların boya konsantrasyonu sırasıyla 35,1 mg/L ve 42,3 mg/L olarak belirlenmiştir ve kırmızı ve mavi renkli atık su çözeltilerinde %80 civarında renk giderimi sağlanmıştır. Renk giderimi mavi atık su çözeltisi için yaklaşık üç kat daha hızlıdır. Kırmızı renkli atık sularda 240 dakikada %76 oranında renk giderimi; mavi renkli atık sularda ise 70 dakikada %82 oranında renk giderimi gerçekleşmektedir. Ozonlama ile boyarmaddenin kromofor grubunun parçalanıp parçalanmadığının analizi için, 100 mg/L boya konsantrasyonuna sahip deterjansız çözeltiler ozonlanmış ve dondurularak kurutulmuştur. FTIR cihazı analizleri sonucunda, kırmızı çözeltilerde ozonlama etkisiyle 1540 cm-1 civarında görülen N = N bağının kırıldığı, dolayısıyla azo kromofor grubunun parçalandığı; mavi çözeltilerde ozonlama etkisiyle 1575 cm-1 civarında görülen kromofor grubu temsil eden antrakinon halkasına ait bağların kaybolduğu belirlenmiştir. Ozon ile rengi giderilen suyun kalitesi incelendiğinde, çıkış suyu parametrelerinin giriş suyu parametrelerine göre daha iyi seviyede olduğu saptanmıştır. AKM, bulanıklık, KOİ (%54 düşüş) ve TOK (%35 düşüş) parametrelerinde ozonlama işlemi etkisiyle belirgin düşüş sağlanmıştır. Hazırlanan prototip makinede geri dönüştürülen su bir sonraki çevrimin ana yıkama adımında kullanılmıştır. 10 çevrim süresince ozonlanmış su ile yıkanan çeşitli tekstil numunelerinde herhangi bir tekstil hasarlanma etkisi görülmemiştir. Geri kazanılmış su ve şebeke suyu ile yapılan yıkamaların yıkama performansı değerleri arasında belirgin bir fark tespit edilememiştir. Çamaşır makinesi ozon ile renk giderme sisteminin enerji tüketimi, mavi kumaştan elde edilen suyu ozonlamak için pamuklu 40 programının enerji tüketiminin yaklaşık beşte biri, kırmızı kumaştan elde edilen suyu ozonlamak için pamuklu 40 programının yaklaşık üçte ikisidir. Ozon ile renk giderme sistemine sahip çamaşır makinelerinin yaklaşık dörtte bir oranında su tasarrufu sağlayacağı tahmin edilmektedir. 8-9-10 kg kapasiteli çamaşır makinelerinde çevrim başı yaklaşık 14 L'lik su tasarrufunun bir yılda yaklaşık 1,24 hm3'lük su tasarrufu sağlaması beklenmektedir. Çamaşır makinesi ortamında atık suyun kendi kaynağında renginin giderilmesi, geri kazanımı ve tekrar kullanımı ile sürdürülebilir yaşam desteklenebilecektir. Geliştirilen ürünün hem ticari açıdan hem çevresel açıdan başarı potansiyeli bulunmakta hem de sürdürülebilir ürün gamında kalıcı bir yer edinmesi beklenmektedir.
Fabrication and characterization of biodegradable fibrous webs for vascular graft structures

(Graduate School, 2022-01-10) Öztemur, Janset ; Eniş Yalçın, İpek ; 503181804 ; Textile Engineering ; Tekstil Mühendisliği

Cardiovascular diseases are among the most common types of non-infectious diseases, causing approximately 20 million deaths worldwide to date. Deaths caused by cardiovascular diseases, triggered by the increase in the stress level brought about by settling from rural to urban at the global level and the spread of unhealthy eating habits, increased by 21.1% between 2007 and 2017. According to the World Health Organization data, it is estimated that the annual incidence of cardiovascular disease-related mortality will increase to 23.6 million worldwide by 2030. On the other hand, while the Covid-19 pandemic, which affected the entire world, caused an unexpected increase in cardiovascular diseases, the fact that people with these types of diseases were among the ones defined as a high-risk group once again revealed the seriousness of the situation. Mild cardiovascular diseases are treated with dietary modification, lifestyle changes, and medications, while treatment options for more damaged blood vessels usually consist of bypassing a part of the autologous vessel to replace the diseased part. The use of autologous vessels requires an additional clinical procedure such as vascular integration to the damaged area, as well as taking veins from certain parts of the body such as leg vein, forearm artery, and thoracic artery for this procedure. In addition to the aforementioned risks, dimensional incompatibilities may also occur in some cases. For this reason, the necessity of finding alternative solutions in order to overcome these problems experienced in autologous vessels is among the prominent issues in recent years. Although allografts taken from donors or cadavers and xenografts procured from animals are alternatives, they cannot fully meet this need due to the lack of donor/incompatibility and their short lifespan. Replacing the damaged vessel with a vascular graft in the treatment of cardiovascular diseases is one of the preferred methods of recent times, but problems such as infection formation, risk of thrombosis, incompatibility in radial elasticity, inadequacy in cell development, especially in small-caliber vessel changes, limit surgical success. At this point, the search for new materials and constructions has come to the fore, and the design of biodegradable scaffolds that can be replaced by an autograft produced by the body over time has taken its place among the priority research topics. Although important findings have been obtained in the research that has accelerated in the last 10 years, there is no small-caliber biodegradable vascular graft that has achieved commercial success yet. In order to meet the need, it is expected from the vascular graft to provide structural support and encourage cellular activity for the body to produce its vessel. The most important step in approximating vascular grafts designs to native blood vessel structure is to optimize the surface morphology and develop a microenvironment in which cells can attach and proliferate. For this reason, the features of the graft surface should be well understood and morphological criteria should be determined. Within this thesis, a detailed literature review is realized to understand the native artery structure and an experimental study is carried in three parts including the selection of biopolymers, optimization of solution and production parameters, and morphological, structural, thermal, and chemical analyses of the structures. The first experimental part of the thesis is a preliminary study that includes the selection of biomaterials as well as optimization of solution parameters (polymer concentration and blend ratio) and production parameters (feed rate, voltage, and tip-collector distance). A literature review is performed for surfaces produced by electrospinning using low molecular weight polycaproclactone (PCL) and polylactic acid (PLA) polymers as part of this investigation. The affects of parameters like molecular weight, concentration, and blending ratio on surface morphology, smooth fiber production, and fiber diameter parameters are examined during the research work. Electrospinning parameters are systematically studied, and the influences of these parameters on fiber production are determined. Basic parameters such as voltage, feed rate, and tip-collector distance have been optimized in this context by considering the environment's temperature and humidity, as well as the characteristics of the polymer solution. In the first stage, PCL at 16, 18, and 20 % concentrations, PLA at 7, 8, and 9% concentrations and 12% concentration of PLA/PCL (25/75 and 50/50 ratios) are used for surface formation. In this context, a definite conclusion is reached about the polymers to be used in the thesis by evaluating the performances of the determined parameters in the fibrous surface formation process and the morphological properties analyzed by scanning electron microscopy (SEM); furthermore, polymer solution concentration ranges and blending ratio are determined. The results indicate that the spinnability of low molecular weight PCL (45,000 Mn) is insufficient since either bead formation or thick and discontinuous fiber-like forms are observed in all polymer concentrations while neat PLA and PLA/PCL blends have better spinnability, which allows smooth fiber production. In the second part of the thesis, higher molecular weight PCL (80,000 Mn) is introduced to the fibrous webs in order to take the advantage of its better mechanical properties and spinnability. Similar to the preliminary part, PCL, PLA and PCL/PLA blends are studied, but polymer concentration ranges are kept constant as 6, 8, and 10% for all polymeric structures. The morphologies of the electrospun webs are observed by SEM, also fiber diameter and porosity values are measured. Thus, the polymer concentration at which smooth and fine fibers are obtained is determined for neat PLA and PCL in addition to PLA/PCL blends. The hydrophobicity of the surfaces is evaluated by water contact angle analysis (WCA). Differential scanning calorimetry (DSC) is used to observe the thermal behavior of the surfaces during heating and cooling to investigate the crystallinity of the surfaces that provide insights about biodegradability processes. Although it is not possible to obtain fibers at low polymer concentrations on all polymeric surfaces, 8%, and 10% polymer concentration allow continuous fiber formation; moreover, an expected relationship between fiber diameter and porosity ratio is detected. Surfaces with the finest fibers are those with the highest porosity. On the other hand, the thermal behavior of the surfaces is in line with the literature and the highest crystallinity is that of PCL with about 40%. In the last and final part of the thesis, poly (L-lactide) (PLLA), a derivative of PLA, is also introduced in the study, and its effects on surface properties are investigated. Within the scope of developing the most suitable surface for vascular grafts, which is one of the major objectives of the study, different blending ratios for both PLA/PCL and PLLA/PCL are determined in detail. Similar to previous experimental parts, the structures are mainly subjected to SEM, Fourier-transform infrared spectroscopy (FTIR), and DSC analyses, and the effects of blend ratios on morphological, thermal, and chemical properties are investigated in details. It has been observed that the fiber diameter increases with the increase of the ratio of PLA, which has a high molecular weight, in the PCL structure, but the increase in the ratio of PLLA, which has a lower molecular weight than PCL, in the PCL structure causes a decrease in fiber diameter. It has been determined that the polymer ratio is very effective on the fiber diameter depending on the molecular weight of the polymers, and during the thermal analysis, it determines the characteristic curves in the heating and cooling processes. Selected samples of PLA100, PCL100, PLA20PCL80, PLA50PCL50, PLLA20PCL80, and PLLA50PCL50 are subjected to biodegradability analysis at 1st, 3rd, and 5th months. All samples except PLA20PCL80 showed an increase in degradation rate in consecutive months. It is thought that this exception ocuurs in the PLA20PCL80 because of the measurement accuracy. As expected and as seen in the literature research, the degradation rate of PLA (14.29% and 40%, respectively) at the end of the 3rd and 5th months is considerably higher than that of PCL (2.17% and 3.70%, respectively). On the other hand, it is observed that 50% PLA ratio in the blend considerably increases the weight loss of the surface. Moreover, the addition of PLLA on surfaces is also found to accelerate biodegradation, similar to PLA. Cell analysis (MTS) consists of the proliferation of fibroblast and human umbilical vessel endothelial cells (HUVECs), which are one of the basic cells of the native vascular structure. In the content of MTS cellular analysis, affirmative outcomes are obtained in both fibroblast cells and HUVECs compared to control samples, and it is observed that each surface is a suitable environment for cells to live. Besides, PLA appears to have a positive effect on cell viability on PCL up to 20%, and the highest cell proliferation occurred in the PLA20PCL80 sample. The findings of the experimental studies as detailed in the three stages above shed light on the best way to examine the morphological, chemical, thermal, and biological properties of a wide variety of surfaces produced from PLA, PLLA, and PCL polymers. Surfaces designed and fabricated according to the optimized parameters are promising for layered vascular graft structures. In the studies that will take place in the thesis' continuation, small-caliber vessel grafts will be designed and fabricated from these optimized surfaces with desired orientation levels, taking into account the mechanical properties of the vessels and advanced cell activities both in-vitro and in-vivo.
Improving the comfort properties of spacer fabrics for sportswear applications

(Graduate School, 2022) Karabulut, Ayşe Berna ; Nergis, Fatma Banu ; 779370 ; Department of Textile Engineering

Sportswear is the clothing including footwear, worn during sports or physical exercise and has an increasing demand due to lifestyle changes, increasing both sports organizations and health consciousness of people. The global sports apparel market is estimated to witness a Compound Annual Growth Rate (CAGR) of greater than 7% during the forecast period of 2022 to 2027. Bearing that into mind, it is no surprise to observe that the sports apparel with improved comfort properties have become more popular than ever. As is well known, comfort perception has four different aspects, such as thermo physiological, psychological, sensorial and wear comfort. In general, optimum thermal and moisture regulation, good air and water vapor permeability, rapid moisture absorption wicking and drying property, soft and pleasant touch are the most common characteristics sought in sportswear for satisfactory comfort properties. Enhancing the wearer's comfort is possible by engineering fabric structures by incorporating suitable fibers. For doing so, in this study, bilayered spacer fabric samples were produced with two different materials, on a Mayer & Cie Relanit 28 fine circular interlock knitting machine (30 inches in diameter and 92 feeders). 78/60x1 dtex S and Z twisted Recycle PA66 textured yarn (P) and 78/72 dtex S and Z twisted PA6-Umorfil textured yarn (U) together with 44 dtex Elastane were used for knitting both or one of the sides of the spacer samples. 22/1 dtex PA6 FDY monofilament yarn was employed as the spacer yarn. The samples were tested both in greige and dyed state and were conditioned under the standard atmosphere conditions (20 0C ±2, 65 % ±5%) before testing. Yarn and fabric tests, such as thickness, air permeability, stiffness, contact angle, water vapor permeability, wicking, drying rate, were conducted in accordance with the relevant standards. Comfort properties of fibers can be used in different parts of the garments depending on the intended use and purposes. Making the inner side of fabric as rcy-PA66 and the outer side of fabric as Umorfil gives cost saving production with improved comfort properties.
Investigation of laser fading and effect of preparation processes on laser faded fabric quality

(Graduate School, 2022) Uysaler, Tuna ; Özcan, Gülay ; 503171806 ; Textile Engineering Programme

In the textile industry, laser technology is used to achieve effects on textiles in both micro and macro levels by changing the structure of fibers, since the 19th century. Laser fading is one of the main process of laser technology and is commonly used in denim. Fabric surface from 0.1mm to 0.5mm is processed and faded with this method. Resolution and pixel time are crucial parameters of laser source influencing the result of laser treatment. Resolution controls the density of laser dots per unit area, which is expressed in dpi (dots per inch). Pixel time, expressed in µs, controls the required time to place the laser beam at each point. Longer pixel time means more energy and so higher degree of fading effect. With the increase of pixel time and resolution, laser power density increases. Laser fading is a dry and computer-controlled process. Less manpower is required in this method. No or fewer consumables are used and there is no toxics caused by the disposal of products as on conventional wet finishing methods. With the arrangement of laser processing parameters at the desired level, it provides fast, precise and accurate production with sufficient reproducibility and repeatability, without environmental and health problems. Despite these advantages, laser fading may cause decrease in mechanical properties and higher yellowness on the color of the fabric. In this thesis, firstly, it was aimed to identify the most effective conditions of denim fading by laser treatment with different laser parameters followed by enzyme washing. Secondly, it was intended to observe the effects of chemical pre-treatment applications before laser fading at the optimum laser parameters reported, following by simple rinsing instead of enzyme washing, thereby minimizing the disadvantages of conventional laser fading (laser fading followed by enzyme washing). For this purpose, two different type of commercially used 100% organic cotton denim fabrics with 3/1 twill construction were selected for experimental study. The first fabric sample denoted as G was 435 gr/mt² and dyed with sulfur bottom and indigo. The second fabric F was 480 gr/mt² and only indigo dyed. CO2 laser machinery with a wavelength of 10.6µm and a power of 60% was used for laser treatment. Resolution and pixel time were set into three different levels; 32, 40, 48 dpi, and 300, 500, 700 µs. Subsequently, all laser-treated fabric samples were exposed to enzyme washing at a liquir ratio of 1:10 at 40°C for 10 min. Rucolase STG New enzyme was used for enzyme washing. Change in fabric unit weight, tensile strength (TS EN ISO 13934-1), abrasion resistance (TS EN ISO 12947-2) were evaluated for all fabrics. Color values (CIE L*a*b*, DE*, h*, C*, and K/S), yellowness and whiteness indexes were measured by Datacolor spectrophotometer. Colorfastness against washing (TS EN ISO 105-C06), rubbing (TS EN ISO 105-X12), artificial light (TS EN ISO 105-B02), water (TS EN ISO 105 E01) and perspiration (TS EN ISO 105 E04) were tested and evaluated under D65 artificial day light using the lightbox. From the first part of the experimental work, optimum laser parameters were reported as 40 dpi resolution and 300 µs pixel time. It was observed that, required fading effect with sufficient mechanical properties and good color values can be obtained with lower tensile strength loss and minimum yellowness with the application of enzyme washing under these determined process conditions. In the second part of experimental work, conditioned G fabric samples were washed with nonionic (0.5 g/L) surfactant at 40 °C for 60 min to remove the impurities and sizing agent and then pre-treated with polysilicic asid (PA), bicarbonate (BC), boric acid (BA), borax (BX) and mixture of boric acid/borax (BA/BX), separately. Chemicals were applied on fabrics with impregnation method at a liquir ratio of 1:10. PH was adjusted to 5-6 with acetic acid. Dried test specimens were exposed to laser fading at determined laser parameters, 40 dpi resolution and 300 μs pixel time. After laser fading, test specimens were rinsed at 40 °C for 40 min. With the pretreatment of polysilicic acid and mixture of boric acid/borax, comperable results to enzyme washing were achived in terms of yellowness and whiteness values. 16% decrease in yelowness was obtained and closest whiteness value to enzyme washing was obtained by 12% decrease in whiteness.Preliminary experiments on chemical pretreatment applications were carried out by using G fabric. Based on the results, the sample pretreated with 40 g/L PA has a comparable whiteness index (80.7) with the lowest ΔE value (0.8) compared to laser-treated and subsequently enzyme-washed G4 sample which the whitness index is 91.9. It was followed by BA/BX application with a WI of 80.2 and DE value of 2.2. Lightness values (L*) of polysilicic acid and bicarbonate applications were the closest ones to enzyme washing with the ratio of 2.5%. Considering the results of preliminary experiments, color values and mechanical properties of PA application in different concentrations; 20 g/L, 30 g/L and 40 g/L and BA/BX application were evaluated for both two fabric types; sulphure/indigo dyed (G) and indigo dyed (F). Chemical pre-treatments were applied in same prosedure. It was reported that, pre-treatment applications on G fabric decreased the yellowness and whiteness values of the fabric caused by laser treatment. Maximum decrease on yellowness was observed with the application of boric acid/borax (BA/BX) pre-treatment by 25%. Minimum decrease in the whiteness index of G fabric was observed with the pre-treatment of 30 g/L Polysilicic Acid by 2.5%. Maximum lightness was performed with 20 g/L polysilicic acid pre-treatment. 30 g/L polysilicic acid application caused highest increase in tensile strength in warp direction by 4% and 40 g/L polysilicic acid application in weft direction by 27.5% compared to enzyme washed, laser faded reference fabric. On the other hand, 40 g/L polysilicic acid pre-treatment decreased the tensile strength by 3.5% in warp direction and the mixture of boric acid/borax caused minimum increment in weft direction by 14.5%. According to Levi's Denim standard, tensile strength values obtained with pretreatment applications were acceptable. It was observed that, yellowness and whitness indexes increased with the pre-treatment applications on the fabric indigo dyed (F) as compared to reference F4 fabric. BA/BX application caused minimum increase by 11% in yellowness with a WI value of 110.0. With the application of 40 g/L polysilicic acid pre-treatment, a WI value of 129.3 was obtained, resulting in an increase of 27% compared to reference fabric. Maximum lightness (L*=26.4) was obtained with 20 g/L polysilicic acid pre-treatment. The highest increase in tensile strength in warp direction of indigo dyed fabric (F) was observed with the pre-treatment of 30 g/L polysilicic acid. Highest increase in tensile strength in weft direction by 36.4% was obtained with 20 g/L polysilicic acid application. 40 g/L polysilicic acid pre-treatment has the lowest increase in tensile strength for warp direction as 1.5% and caused a decrease in weft direction by 2.5% which is also in the range of tensile strength values specified in Levi's Denim standard. As can be seen from findings obtained in this study, lower yellowness and higher whitness values were obtained on laser faded sulphure and indigo dyed G fabric with pre-treatment applications. However, for indigo dyed F fabric, whiteness index increased but there was also a slight increase in yellowness with pre-treatments. Pre-treatment of polysilicic acid and mixture of boric acid/borax provided suitable fading effects compared to laser faded and subsequently enzyme washed reference samples while maintaining the mechanical properties. Considering higher or comparable whiteness index, lightness and tensile strength values both in warp and weft directions and minimum yellowness, it can be suggested that for sulphure/indigo dyed 100% organic cotton denim fabric, 30 g/L and 40 g/L polysilicic acid pre-treatments before laser fading can be done followed by simple rinsing, instead of enzyme washing. With the application of 30 g/L and 40 g/L polysilicic acid pre-treatment, whiteness value remains almost the same with enzyme washing and yellowness values decreases by 32% and 35% respectively. The pre-treatment of the mixture of 10 g/L boric acid and borax can be recommended for the indigo dyed 100% organic cotton denim fabric. By this pre-treatment, yellowness and whiteness of the fabric remain the same as laser faded and enzyme washed reference fabric with 35% increased tensile strength in weft direction. It is concluded that, by chemical pre-treatment applications before the laser process, the mechanical properties of laser-faded denim fabric can be preserved by eliminating the enzyme washing, which reduces the tensile strength up to 25%. Besides, all after-treatments were performed with the usage of water, no additional chemicals were used. Thus, environmentally friendly, ecological processes with sufficient denim fading effect, recommended in the market, can be obtained without any enzyme washing.
Investigation of mechanical properties of small caliber fibrous vascular grafts

(Graduate School, 2023) Özdemir, Suzan ; Eniş Yalçın, İpek ; 817996 ; Textile Engineering Program

Cardiovascular diseases remain the most common cause of mortality worldwide, resulting in the deaths of 17.9 million people in 2019. Furthermore, previous cardiovascular diseases are a significant risk factor for COVID-19-related complications and deaths. According to the World Health Organization, the number of deaths would increase by 24.5% by 2030. The most frequent type of cardiovascular disease is coronary artery disease, which necessitates a surgical procedure called bypass grafting that involves arterial replacement. In bypass surgery, an autologous vein or synthetic graft is used to restore a diseased blood vessel that has become damaged or clogged. However, autologous grafts pose significant challenges due to scarcity and difficulties in graft harvesting operations. On the other hand, commercial synthetic ones are also problematic to be used as smaller diameter vascular grafts (< 6 mm) due to poor patency rates, thrombogenicity, and compliance mismatches, as well as neointimal hyperplasia in the peri-anastomotic regions. The compliance mismatch between the native vessel and the rigid synthetic graft at the anastomosis sites results in low blood flow rates and turbulent blood flow in small-diameter grafts. These mechanical issues lead to thrombosis and luminal narrowing due to intimal hyperplasia, which results in poor long-term patency, together with the thrombogenicity of the scaffold material and a lack of endothelialization. In order to address the demand for suitable scaffolds that can be utilized in bypass procedures by using new materials and production processes, researchers have concentrated on building an alternative tissue-engineered small-caliber vascular graft that can imitate the native artery in all ways. There is currently no small-caliber biodegradable vascular graft that has reached commercial success, despite the fact that significant breakthroughs have been made in the research that has intensified in recent years. The vascular graft is supposed to give structural support and promote cellular activity for the body to generate its vessels. The fundamental difficulty with vascular tissue engineering is still creating a perfect vascular graft that can replicate the structural, biological, and mechanical characteristics of the native blood vessels and be used in place of the disabled blood vessel. In this context, morphology and cellular analysis are typically given top priority, whereas mechanical aspects are only briefly discussed. To improve the clinical performance of vascular grafts, expose physiological stresses, and prevent graft failure brought on by intimal hyperplasia, thrombosis, aneurysm, blood leakage, and occlusion, it is essential to create grafts with good mechanical qualities comparable to native vessels. The mechanical characteristics of scaffolds, such as compliance, burst pressure, nonlinear elasticity, modulus, and suture retention strength, must match those of the native tissues because even a slight mechanical mismatch between the graft and the native vessel can cause graft failure. The mechanical properties of the vascular grafts are significantly influenced by the material and design. In this thesis, a detailed literature review was carried out to understand the native blood vessel structure and to provide a broad and comparative overview of recent studies on the mechanical properties of fibrous vascular grafts, with an emphasis on the effect of structural parameters on mechanical behavior in the experimental part. The purpose is to shed light on the design parameters needed to maintain the mechanical stability of vascular grafts that can be used as a temporary and biodegradable backbone, allowing an autologous vessel to take its place. An experimental study is carried out to produce fibrous vascular scaffolds made out of various biopolymers and their combinations with different fiber orientations and constructions and assess their physical, morphological, and mechanical properties. The first experimental part of the thesis is a preliminary study that includes the production of planar and tubular scaffolds made of neat PCL and PLA and their blends with the PCL/PLA blending ratios of 90/10, 80/20, 70/30, 60/40, and 50/50 by using an open system electrospinning unit. PCL is a flexible biopolymer with a long biodegradation time, whereas PLA is a strong polymer with high brittleness, higher biocompatibility, and a faster biodegradation time than PCL. The reason for utilizing these polymers together is to combine their mechanical and biological advantages and eliminate their inadequacies. The effect of the polymers and collector type on the fiber morphologies, diameters, and orientations, sample thickness, as well as the mechanical properties was assessed. It was observed from the results that all the samples were successfully produced, and they all have distinctive morphologies with smooth and continuous fibers. The tensile stress and elongation results revealed that polymer composition is highly effective on the tensile properties. Neat PCL samples had considerable elongation value with 390% whereas PLA showed good tensile strength with 2.73 MPa. When the blended samples were observed, it was seen that the blending affected the mechanical properties negatively based on the blending ratio that was used because of the immiscible characteristics of the polymers. The addition of PLA gradually improved the tensile properties, while using PCL in higher amounts caused better elongation values in blended samples, which shows the importance of the selection of a suitable blending ratio. According to the results of the planar samples, the PCLPLA90 and PCLPLA80 samples can be selected as they have moderate stress and strain values among the blended samples. Also, the use of tubular collectors enables the production of scaffolds with desired construction. On the second part, the monolayer tubular vascular prostheses were produced in a closed electrospinning system by using two rotational speeds to achieve scaffolds with randomly distributed or radially oriented fibers. In addition to the neat and blended samples made of PCL and PLA, two more polymers were added to the production stage, which are PLCL and PLGA. As PLCL is the copolymer of PCL and PLA and thought of as a better candidate to be used instead of physically blended scaffolds to eliminate the mechanical failure caused by blending, it was also used in the vascular graft fabrication process. On the other hand, PLGA has good biocompatibility and faster biocompatibility with good mechanical properties, which make it a good option to be used in vascular applications. When the physical and morphological results were investigated, it was seen that in a closed system, it is possible to produce vascular grafts with the desired thickness levels. Fiber orientation was also observed from SEM images in the radial direction within the tubular samples produced by using a high collector speed. The tensile test was performed on all the tubular samples in longitudinal and radial directions to see the effect of polymer composition, fiber orientation, and test direction on the tensile properties of the specimens. Results revealed that the neat PCL scaffolds showed more flexibility than the neat PLA samples, and the neat PLA samples show higher tensile strength than the neat PCL samples in general. Also in blended samples, tensile stress and elongation values were improved in some cases depending on the blending ratio, such as in PCLPLA90 and PCLPLA80 specimens. Also, neat PLCL samples had both higher elongation and strength values than all neat and blended scaffolds, with some exceptions. Generally, when the PLA ratio is increased, the tensile strength improves gradually, whereas the elongation values decrease. The maximum tensile strength belonged to PLCL100_O in the radial direction with 12.12 MPa, whereas it showed its highest elongation in the longitudinal test direction with 832%. In addition, PLGA100_R showed higher strength than the samples made of PCL and PLA, with very limited elongation. The strength values of PLGA samples were really promising, as it is a rigid polymer. On the other hand, radial fiber orientation greatly contributed to the tensile stress values in the radial direction and the elongation values in all directions compared to the samples with randomly oriented fibers. Higher stress values were obtained in the direction of the orientation whereas higher elongation values were achieved in the direction without fiber alignment. On the other hand, a custom-designed test device was specifically designed for vascular graft specimens to measure their burst strength and compliance. When the burst pressure values were assessed, the best results were obtained from the vascular grafts made of PLGA and then PCL/PLA blends with radial fiber orientations. The addition of PLA results in an increment in burst pressures up to a certain limit of PLA ratio. PLGA100_O showed the highest burst pressure at 2889 mmHg. According to the compliance measurements made using three different physiological blood pressure ranges, the scaffolds with higher flexibility possessed better compliance values. Thus, the samples with randomly distributed fibers had the highest compliance results when compared with the samples consisting of radially oriented fibers. PLCL100_R demonstrated the highest compliance with 4.924 mmHg %/100 mmHg at a 50–90 mmHg pressure range as the most flexible biopolymer among the others. Finally, considering the previously obtained biological analysis results, bilayer vascular grafts were fabricated by combining monolayer scaffolds with the best mechanical properties to obtain a prosthesis that could mimic the topography of the natural artery. The inner layer was constructed from randomly distributed fibers, whereas the radially oriented fibers were included in the outer layer. PCL100_R and PCLPLA80_R monolayers were selected as the inner layers while PLCL_O was used in the outer layers of the bilayered grafts due to their appropriate mechanical advantages. Results indicated that although the samples had a delamination problem in some cases, they had improved mechanical advantages in the tensile and bursting testing processes. On the other hand, the compliance results were still sufficient and comparable with the native blood vessels. All the results that have been achieved in this thesis shed light on the examination of the mechanical properties of vascular grafts and contain significant information for vascular prostheses to be produced in further research. The bilayered grafts that will be constructed in the future studies will be designed by considering the results of the mechanical assessments of the samples that have been optimized by using PCL, PLA, PLCL, and PLGA within the scope of this thesis and the biological examinations. In the following process, it is aimed to switch to in-vivo studies with the most appropriate bilayer scaffold designs to be obtained and to study the biological process in an interdisciplinary manner.

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