LEE- Tekstil Mühendisliği-Yüksek Lisans

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http://hdl.handle.net/11527/19466

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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.
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.
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.
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.
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.
Isı pompalı tamburlu kurutucularda tambur devri ve hava debisinin tekstillerde boyutsal değişim, boncuklanma ve lif salınımına etkisinin incelenmesi

(Lisansüstü Eğitim Enstitüsü, 2023-01-06) Çoban, Muhammed Emin ; Özcan, Gülay ; 503191803 ; Tekstil Mühendisliği

Bu tez çalışmasında ısı pompalı kurutma makinelerinde tambur devri ve hava debisi parametrelerinin boyutsal değişim, boncuklanma ve lif salınımına etkisi araştırılmıştır. Tambur devri 30, 41, 52 ve 63 devir/dakika olacak şekilde 4 farklı seviyede, hava debisi ise 35, 47 ve 59 litre/saniye olacak şekilde 3 farklı seviyede incelenmiştir. Tambur devri ve hava debisi seviyeleri full faktoriyel olarak test tasarımı yapılmış toplamda kurutma makinesi için 12 farklı koşul denenmiştir. Koşullar 5 tekrar ve makine kapasitesinin yarısı dolulukta (4 kg) olacak şekilde tamamlanmıştır. Deney sonuçları istatistiksel olarak analiz edilmiş; ısı pompalı tamburlu kurutma makinelerinde boyutsal değişim, boncuklanma ve lif salınımı hasarlarını azaltacak optimum kurutma programı oluşturulmuştur. Ayrıca, farklı kurutma yöntemleri de boyutsal değişim, boncuklanma ve lif salınımı için test edilerek sererek kurutma, tamburlu kurutucu referans pamuklu programında kurutma ve yeni geliştirilen optimum programda kurutma karşılaştırılmıştır. Deneysel çalışmada kullanılacak numuneler belirlenirken öncelikle her hasar türü için en çok hasarlanan ve kullanımı yüksek olan kumaşlar tespit edilmiştir. Boyutsal değişim hasarı için pamuklu örme yapılar ön plana çıkarken, boncuklanma için kesikli polyester içerikli kumaşlar ön plana çıkmıştır. İplik yapısı olarak ring iplik türü hem her iki hasarın oluşmasında etken olarak rol oynaması hem de en yaygın kullanılan tür olması sebebi ile tercih edilmiştir. Lif salınımı konusunda pamuk gibi doğal liflerin polyester gibi sentetik liflere oranla çok daha fazla şekilde lif oluşturması ve ayrıca örme yapıların da lif salınımını artırması nedeniyle lif salınımı için pamuklu örme kumaşlar tercih edilmiştir. Bu bilgiler ışığında, %100 pamuk, %95/5 pamuk/elastan, %70/30 pamuk/polyester ve %100 polyesterden oluşan süprem örme yapısına sahip kumaşlar boyutsal değişim ve boncuklanma hasarlarını tespit etmek için kullanılan test numuneleri olarak seçilmiştir. Lif salınımı için tekstil tipine göre lif salınımı bakılmamış, hem müşteri karışım oranını temsil etmesi hem de lif salınımını göstermesi için 4 kg müşteri karışım yükü oluşturulmuştur. 4 kg yükün 1.5 kilogramı %100 pamuk süprem, 1.5 kilogramı polyester ballast yük, 0.5 kilogramı standart havlu ve 0.5 kilogramı boyutsal değişim ve boncuklanma numuneleri olan 4 farklı içerikteki süprem kumaşlar olmuştur. Boyutsal değişim ve boncuklanma 1., 3., ve 5. tekrarlarda ölçülmüş, lif salınımı ise 5 tekrar olacak şekilde her tekrarda ölçülmüştür. Boyutsal değişim ve boncuklanma için ayrıca mikroskop altında incelemeler yapılmıştır. Boyutsal değişim test sonuçları istatistiksel olarak analiz edildiğinde, büyüklük sırasıyla, tekstil tipi, tekrar sayısı, tambur devri ve hava debisinin tekstil çekmesinde etkili faktörler olduğu görülmüştür. Bütün boyutsal değişimler çekme olarak görülmüştür. Tekstil tipleri kendi içinde gruplandırma yapıldığında %100 pamuk kumaş en çok çekme gösteren kumaş olmuştur, ikinci sırada %95/5 pamuk/elastan kumaş yer almış ve en az çeken kumaş türleri ise %70/30 pamuk/polyester ve %100 polyester kumaş olmuştur. Tekstil tipi için dikkat çeken sonuç %70/30 pamuk/polyester karışım kumaşın %100 polyester kumaş ile çekme seviyelerinin istatistiksel olarak birbirinden ayrışmaması, karışım kumaşın %100 polyesterin çekmesine çok yakın gelmesi olmuştur. Pamuklu kumaşlara oran olarak az da olsa polyester eklemenin çekme problemini çok yüksek derecede iyileştireceği sonucuna varılmıştır. Tekrar sayıları kendi içinde gruplandırıldığında her tekrar farklı bir gruba düşerek istatistiksel olarak ayrışmıştır. Tekrar sayısı arttıkça çekme derecesi de artmış fakat artış hızı giderek düşmüştür. Tambur devirleri kendi içinde gruplandırıldığında 52 devir en çok çekmeye neden olmuş, 30 ve 41 devirler orta seviyede çekme göstermiş ve 63 devir ise çekme hasarını en aza indiren devir olmuştur. 30 ve 41 gibi devirlerin 52 devre göre tekstillere daha düşük seviyede mekanik kuvvet uygulaması nedeni ile çekmede azalma sağladığı tespit edilmiştir. 63 devirde ise yüksek hızdan dolayı kumaşlar tambur çeperine yapışmakta herhangi bir mekanik kuvvet söz konusu olmamaktadır, bu sayede çekme hasarının en aza indirilmesi sağlanmıştır. Tekstil bazlı olarak tambur devrinin etkisi incelendiğinde 63 devrin %100 pamuklu tekstillerde çok daha bariz bir şekilde fark oluşturduğu görülmektedir. Bu fark tekstilin içine polyester eklenince azalmaktadır fakat 52 devir polyester içerikli tekstiller için her zaman en kötü sonucu vermiştir. Hava debileri kendi içinde gruplandırıldığında ise yüksek hava debisi (59 L/s) orta ve düşük hava debisinden daha yüksek ve istatistiksel olarak farklı çekme değerine sahip olmuştur. Yüksek hava debisinin tekstillere uygulanan mekanik kuvveti arttırıp tekstillerin daha fazla ve sert bir şekilde hareket etmesine neden olduğu ve bu nedenle çekmeyi arttırdığı düşünülmektedir. Ayrıca tekstil bazlı olarak hava debisinin etkisi kontrol edildiğinde, pamuklu içerik arttıkça hava debisinin yüksek olmasının çekmeyi arttırdığı, polyester içerik arttıkça hava debisinin düşük olmasının çekmeyi arttırdığı tespit edilmiştir. Pamuktaki artış mekanik hareket ve hızlı kuruma kaynaklı, polyesterdeki artış ise debinin düşmesi ile beraber artan sıcaklık kaynaklı olmuş olabileceği düşünülmektedir. En çok çeken %100 pamuklu numune mikroskop altında incelendiğinde ise örmedeki boşluk yapısının yıkama ve kurutma işlemlerinden önceki haline göre daha kapalı ve sıkı olduğu gözlemlenmiş, birim alana düşen ilmek sayısının arttığı tespit edilmiştir. Boncuklanma test sonuçları istatistiksel olarak analiz edildiğinde, tekstil tipi ve tambur devrinin etkili, hava debisinin ise etkisiz parametre olduğu tespit edilmiştir. Tekstil tipleri kendi içinde gruplandırıldığında, %100 pamuk ve %95/5 pamuk/elastan numuneler 5 tekrar sonrası boncuklanma oluşturmayarak bir gruba, %70/30 pamuk/polyester bir gruba ve %100 polyester ise diğer bir gruba ayrılmıştır. En düşük boncuklanma derecesi yani en çok boncuklanan numune polyester numune olmuştur. Kesikli polyester lifler, kumaş yüzeyinde oluşan tüylenmenin yüzeyden düşmesini iplik yapısına uzun ve sert olmaları sebebi ile tutunduklarından dolayı engellediği ve bu nedenle boncuklanma oluşumunu arttırdığı tespit edilmiştir. Pamuk/polyester karışım da %100 polyester gibi yüksek boncuklanma göstermiştir. Tambur devirleri gruplandırıldığında, sadece 63 devir diğer devirlerden ayrı bir grupta yere almış ve en düşük boncuklanmayı göstererek, en yüksek boncuklanma derecesini almıştır. Ayrıca, tekrar sayısının boncuklanmaya etkisi ayrı olarak incelendiğinde 1., 3. ve 5. tekrarın birbirinden ayrıştığı, tekrar sayısı arttıkça boncuklanma gözlemlenmeye başlandığı ve arttığı tespit edilmişitir. Boncuklanma yapıları mikroskop altında incelendiğinde, %100 pamuk ve pamuk/elastan numunelerin yüzeyinde sadece tüylenme olduğu, pamuk/polyester karışımda olan boncuklanma yapısının kumaş yüzeyine yakın, yapı olarak büyük ve içerik olarak çoğunlukla pamuk liflerinden oluştuğu, %100 polyester numunelerde ise boncuk yapısının yüzeyden daha uzakta, yapı olarak daha ince olduğu tespit edilmiştir. Pamuk/polyester karışım numunede yüzeydeki pamuk lifleri uzun bir polyester lifinin onları sarması ve kumaşa bağlaması ile boncuklanma yapısı oluşturduğu da gözlemlenmiştir. Ayrıca, pamuk içeriğe sahip kumaşlarda kir gibi yüzey kalıntılarının da boncuklanma başlattığı tespit edilmiştir. Lif salınımı test sonuçları istatistiksel olarak analiz edildiğinde tekrar sayısı ve tambur devri etkili, hava debisi ise etkisiz parametre olarak bulunmuştur. 5 tekrar sayısı 4 gruba bölünmüş, 1., 2., 3. ve 5. tekrarlar ayrı gruplarda bulunmuşlardır, 4. tekrar ise hem 3. hem de 5. tekrarla istatistiksel olarak ayrışamamıştır. En yüksek lif salınımı 1. tekrarda olmuş, tekrar sayısı arttıkça lif salınımı düşmüştür. Lif salınımının düşmesindeki ivme tekrar sayısı arttıkça azalmıştır. Tambur devirleri gruplandırıldığında, 30 devri en yüksek lif salınımına neden olurken, 40 ve 52 devir orta seviyede lif salınımına sebep olmuş ve 63 devir ise en düşük lif salınımına sebep olmuştur. Lif salınımında 30 devrin en yüksek lif salınımına sebep olmasına kumaşların birbirleri ile olan sürtünmesinin en yüksek derecede olduğu devir olması ve ayrıca düşük devirde dönüldüğü için kurutma süresi ve alınan mekanik darbe süresinin artması etkili olmuştur. Hava debisi lif salınımında direkt olarak etkili olmamış fakat, tambur devri ile ikili etkileşimi istatistiksel olarak etkili parametre olmuştur. Düşük devirlerde (30, 41 devir/dk) yüksek hava debisi (59 L/s), yüksek devirlerde (52, 63 devir/dk) ise düşük hava debisi (35 L/s) kullanımı lif salınımının azalmasında etkili olmuştur. Test sonuçları ile yapılan istatistiksel çalışmada kurutma makinesi parametreleri olan tambur devri ve hava debisi; boyutsal değişim, boncuklanma ve lif salınımı tekstil hasarlarını en aza indirmek için optimize edildiğinde tambur devri 63 devir/dk, fan debisi 35 L/s olarak belirlenmiştir. Belirlenen optimum koşulda test sonuçlarının tekrarlanabilirliği kontrol edilmiş ve doğrulanmıştır. Boyutsal değişim, boncuklanma ve lif salınımı hasarları, kurutma yöntemi değişimine göre de kontrol edilmiştir. Boyutsal değişim ve boncuklanma hasarları sererek kurutma, tamburlu kurutucu pamuklu programında kurutma ve yeni geliştirilen optimum algoritma ile kurutma olarak üç farklı kurutma metodu kullanılarak karşılaştırılmıştır. Lif salınımı karşılaştırma testlerinde ise sererek kurutma test edilmemiştir. Boyutsal değişim %100 pamuklu kumaş üzerinden bakılmış, sererek kurutmada %4.78, kurutucu pamuklu programında %9.08, yeni geliştirilen algortimada ie %5.78 olmuştur. Mevcut kurutucu programına göre %3.3 daha az çekmiş, bu da yaklaşık olarak bir beden çekmenin kurtarılması anlamına gelmektedir. Boncuklanma testlerinde boncuklanma gösteren pamuk/polyester karışım, %100 polyester kumaş test edilmiş, sererek kurutma ile optimum algoritma aynı seviyede boncuklanma oluşturmuş, mevcut kurutucu pamuklu programı ise yarım seviye daha kötü boncuklanma göstermiştir. Yeni geliştirilen algoritma ile tamburlu kurutmanın neden olduğu pilling ortadan kaldırılmıştır. Lif salınımı, hem 5 tekrarın ortalaması hem de toplamı açısından karşılaştırıldığında yeni geliştirilen optimum algoritma mevcut pamuklu programa göre %62 daha az lif salınımı oluşturmuştur. Bütün sonuçlara beraber bakıldığında kurutucularda bulunan mevcut pamuklu programa göre 1 beden çekmenin kurtarıldığı, boncuklanma etkisinin ortadan kaldırıldığı ve lif salınımının %62 azaltıldığı yeni bir optimum algoritma geliştirilmiştir.
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 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.
Tekstilde ERP (enterprise resource planning) kullanımı ve var olan bir ERP yazılımının geliştirilmesi

(Lisansüstü Eğitim Enstitüsü, 2024-07-01) Öztürk, Büşra Nur ; Karakaş, Hale ; 503211804 ; Tekstil Mühendisliği

Kurumsal kaynak planlama (ERP), işletmenin tüm kaynaklarını verimli/etkin şekilde kullanması için tasarlanmış bir sistemdir. ERP sistemleri, şirketlerin hedeflerine ulaşmasındaki temel süreçleri ve fonksiyonları birleştirir, iş uygulamalarının çoğunun entegre olarak yürütülmesini sağlar. Bu sistemler sayesinde işletmedeki bölümler arasında bilgi akışı olmakta ve iletişim sağlanmaktadır. Bununla birlikte tekstil sektörü birçok sektörden farklı bir ürün yapısına sahiptir. Örnek olarak konfeksiyon firmalarında sipariş mantığı ile çalışılmaktadır. Varyantlar, sezonlar, aksesuarlar, prosesler gibi standardize edilemeyen özellikleri bulunmaktadır. Bu nedenle sektörden bir firmanın ERP sistemi seçerken özelliklerine uygun bir yazılım seçmesi gerekmektedir. Bu çalışma denim üretiminde kullanılan bir ERP sisteminin sektörün gerekliliklerini karşılaması adına ERP modüllerindeki eksikliklerin iyileştirilmesi üzerine yapılmış ilk akademik çalışmadır. İstanbul merkezli, denim ve non-denim hazır giyim üretimi gerçekleştiren, sektörün önde gelen anonim bir firmasında çalışmalar yapılmıştır. Microsoft SQL veri tabanı kullanılmış olup, arayüz tasarım geliştiricide Delphi dili ve C# dili kullanılmıştır. Tespit edilen sorunlar sırasıyla, numunelerin fiziki olarak takibinin yapılamaması, kumaş toplarının farklı LOT ve özelliklerde üretime çıkışının yapılması, stok takibinin ve depo düzeninin sağlanamaması, fiziksel kimyasal test laboratuvarındaki testlerin sistemsel olarak bir kaydının tutulmamasıdır. Numune takibini sağlamak için süreçteki her aşamaya bir üretim hareketi tanımlanmıştır ve her aşamada bu hareketler okutularak sistemde tutulmuştur. Yanlış kumaş topu çıkışını engellemek için top rezervasyonu arayüzü tanımlanıp, topun siparişe rezervasyonu yapılmadan çıkışı engellenmiştir. Depolarda fiziki düzenin sağlanması ve stok takibinin yapılması için el terminali cihazı veri tabanına bağlanmıştır. Test verilerinin kaydı için iki arayüz oluşturulup müşterilerin isteklerine göre test seçimi sağlanmış ve sonuçlarının girilip otomatik geçti-kaldı sonucunun gösterildiği bir geliştirme yapılmıştır.
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.

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