LEE- Polimer Bilim ve Teknolojisi-Yüksek Lisans
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ÖgePreparation and adsorption behaviour of hydrophilic adsorbents using high internal phase emulsions(Graduate School, 2025-06-26)Water pollution is one of the most major problems for a sustainable life. Especially dyes, which are one of the biggest sources of wastewater, also pollute the environment significantly. The large amounts of dyes produced in industries into water resources causes this problem to arise, for example, about 7 × 107 tons of synthetic dyes were produced. At this point, especially textile industries use about 10,000 tons of dyes per year, causing the dye solution to leach into water sources. Another negative impact of wastewater resulting from the dye solution is that discharging as wastewater into aquatic environments poses serious ecotoxicological threats on living organisms. Besides fish, other aquatic organisms such as microalgae are also adversely affected by dye wastes, the consumption of these can cause human health problems such as cramps, fever and hypertension. Methylene Blue is a cationic dye widely used in various textile fabrics and its chemical structure contains aromatic amines, potentially causing carcinogenic, toxic effects and non-biodegradable can cause a serious threat to human health. In the view of ecological effect, it decreases oxygen solubility, affects the photosynthetic activity of aquatic life, and decreases the diversity inhibits the synthesis of chlorophyll after dye exposure and reduces photosynthetic rate and consequently the photosynthetic activity of aquatic life. That is why, the removal of methylene blue is essential to the removal of methylene blue is essential to reduce impacts on the environment and living organisms. Adsorption is a suitable method for the removal of dye particles in waste materials. The fact that the structure of the adsorbent has a decisive role on the progress of adsorption makes the synthesis method of adsorbent important. One of the method production of adsorbent is high internal phase emulsion composed of external and internal phase forming 74 % or more of emulsion, which is a versatile technique based on adjusting pore volume, pore size and distribution. In this thesis, crosslinked highly porous volume polymers were prepared with a high internal phase emulsion method (HIPE). Polymerization of the external aqueous phase composed of monomers with 80% organic internal phase gave a flexible and elastic monolith polyHIPE structure and after extraction of internal phase then powdered. The presence of sulfonic groups in the monomer structure provided no longer need of modification steps and enabled loading of high functionality on pore structures. To evaluate the methylene blue adsorption on based polyhipe adsorbents, a variety of parameters were used to detect its effect on adsorption capacity. As as result of all adsorption experiments, the maximum adsorption capacity of the adsorbent was, found as 1483 mg/g for methylene blue, pseudo second order kinetic and langmuir isotherm were obtained more convenient compared to pseudo first order kinetic and freundlich isotherm.
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ÖgeSynthesis and characterization of phosphorus and boron containing flame retardant rigid polyurethane foam(Graduate School, 2025-02-18)Polyurethane materials were scientifically demonstrated through the polymerisation system between diisocyanate and diols with the discovery of Otto Bayer. Polyurethane materials, which have a wide range of products, are frequently encountered in daily life. The industries it serves are based on flooring, automotive, aerospace, construction-insulation, and CASE industry. Industrial product groups of polyurethane foams consist of flexible and rigid polyurethane foams. This study focuses on rigid polyurethane foam materials. These materials are materials that can easily combust in the ambient atmosphere due to their organic structure as well as the excellent strength feature they have by nature. Flame retardant additives added to the structure are aimed to minimise the effects of the fire scenario. Flame retardant technology is one of the widely researched topics in the literature. The content of flame retardants is very critical when considering the environmental effects after combustion. Toxic chemicals (especially halogen-containing structures) in the flame retardant content during the smoke release after combustion cause adverse effects on human and environmental health. The TDB flame retardant structure synthesized in this study is halogen-free and based on the synergistic effects of phosphorus, nitrogen and boron. TDB was designed as a flame retardant by synthesising THEIC containing triazine-trione ring in two steps by means of esterification reaction of boric acid and DPCP. TDB flame retardant synthesised for use in the formulation of rigid polyurethane foams was loaded at chemical compositions of 5%, 10%, 15% according to polyol. Rigid polyurethane foams prepared by one shot free rise method were blown in moulds for characterisation tests. In addition to the flame retardant properties of flame retardant TDB, the morphological structure, mechanical properties, thermal insulation ability and thermal stability of foam cells were investigated. Flame retardancy profile, LOI and Cone calorimeter tests show that the flame retardancy profile of the foams containing 10% TDB is improved compared to neat RPUF. LOI value reached from 18,8% to 20,8%. It is proved by cone calorimeter test results that the total heat release rate decreases with the effect of TDB content. In this context, in line with the characterisation tests, TDB is considered to be a flame retardant compatible with the structure of RPUF.
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ÖgeElectromagnetic shielding and acoustic properties of recycled carbon black enhanced polyurethane(Graduate School, 2025-01-03)Polyurethanes are a group of polymers with various forms, that can be easily modified according to their usage area and are widely preferred in the industry. They are materials that can meet the needs of the industry for various application areas thanks to their superior mechanical properties, insulation performance, durability, low density, and easy production capabilities. In recent years, the automotive industry has been transitioning to systems that can operate with more environmentally friendly resources, in line with the sustainability targets accepted by the world and the net zero carbon emission targets accepted by the Paris 2050 agreement. Electric vehicles are designs that most automotive companies put on their agenda and offer in the markets to achieve these determined goals. Still, like every new technology, these technologies have some points that are open to improvement. The goal of increasing the driving range of electric vehicles is one of the main issues open to development. According to research, weight reduction achieved by using materials with lower density but the same properties in cars leads to fuel savings and decreased emission values while also allowing for increased driving range. Studies indicated that every 10% weight reduction in automotive results in 7% automobile fuel savings. One of the main issues discussed is vehicles N.V.H. (Noise, Vibration, Harshness) problem. Due to the operating principles of traditional vehicles, they produce sounds at low and medium frequencies and thus dampen sounds at the same and lower frequencies coming from outside the car. Since electric vehicles do not have a sound source at these frequencies, materials with acoustic barrier properties have become very important in electric vehicle designs so that the sounds originating from the wheels and traffic coming from outside the vehicle do not disrupt the comfort of the drivers. The negative effects that arise with the electrification of vehicles are another problem that is tried to be eliminated with the right material choices. Frequencies produced by electrical devices can interfere with the frequencies of other devices and thus potentially cause loss of function in devices and pave the way for data leakage, which is one of today's biggest problems. Not only the functions of the devices but also exposure to these frequencies for a very long time affects human health physically and psychologically. While materials with electromagnetic shielding properties minimize these effects, they have become another material group used in electric vehicles. These materials eliminate negative effects by damping the frequencies produced by electronic devices, thanks to the conductive metal or carbon-based additives they contain in their structures. Generally, carbon-based additives (Carbon Fiber, Carbon Black, Graphene, Carbon Nanotube, etc.) can be preferred with polymer matrixes instead of metal additives due to their high density and dispersion problems. In this thesis, the study aims to develop a polyurethane material that can be an alternative to the problems mentioned above. The semi-integral skin of the polyurethane material creates a thick surface on the outer layer, providing the low-density material with a transmission loss feature against sound waves while also providing electromagnetic shielding properties thanks to the carbon black it contains. The carbon black used in this study was obtained from ICARBON company and was obtained by pyrolysis of end-of-life automotive tires at 550C for 2 hours under the N2 atmosphere. In the first phase of the study, the electromagnetic performances of semi-integral polyurethane materials containing 2% and 5% recycled carbon black by weight, mixed with standard type mixer, were examined and compared with semi-integral polyurethane material which has 0.5% recycled carbon black by weight which was dispersed with stator type homogenizer reaching high speeds, to understand the importance of dispersion of additives in the polymer matrix. Electromagnetic shielding properties were analyzed by the waveguide method, and by determining the S21 properties of the materials, shielding efficiency in the 12.4-18 GHz Ku band was calculated for each material group. The result pointed out that the electromagnetic properties of the material produced by stator-type homogenizer were better than the other experimental groups. In the second phase of the study, the ratio of 0.5% by weight was constant, and semi-integral polyurethane materials were mixed by stator-type homogenizer with a constant amount of conductive PANI additive with the same process parameters. DSC, TGA, FTIR, mechanical, acoustic, and electromagnetic shielding properties were compared for each sample group.
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ÖgeEnhancement of interfacial properties for high performance polyethylene fibers produced via gel spinning(Graduate School, 2023)Fibers are materials with high length/diameter ratios, having adjustable fineness, mechanical properties. High performance fibers exhibit excellent mechanical properties such as high modulus, high strength, high abrasion resistance, thermal resistance, low density. One of the methods used to produce high performance fibers is gel spinning, in which the chains are partially entangled in liquid-gel form and connection with each other , rather than solution or melt unlike other methods (dry spinning, wet spinning, melt spinning). In this thesis, ultra high molecular weight polyethylene (UHMWPE) was dissolved in paraffin oil and high performance UHMWPE fibers were obtained by gel spinning method. The gel obtained by dissolving UHMWPE in paraffin oil is formed into filaments by passing through the spinnerettes after extrusion, then passes through the quenching and extraction bath, drying and winding in the final stage. High tensile strength, low specific density, great impact resistance, and exceptional chemical resistance are just a few of the excellent qualities of ultra-high molecular weight polyethylene (UHMWPE) fiber. It is frequently utilized in fishing, aircraft, biomedicine, and ballistic, among other things. UHMWPE fiber has a very high degree of crystallinity (>99%) and macromolecular orientation (>95%), which leads to a high modulus and tenacity of UHMWPE fiber. Gel spinning is a difficult and advanced engineering process. UHMWPE concentration is one of the parameters that determine fiber strength which was kept as 8% wt in this study. For this research, n-hexane was used in the extraction bath to remove paraffin oil from spun UHMWPE fibers. Following the solvent extraction procedure, the fibers undergoing hot drawing with different drawn ratios. The differential scanning calorimeter is used to analyze the thermal and crystallization properties of the fibers in their drawn, undrawn, and gel-state forms. Two newly peaks are observed when DR reached to 40. These peaks shows orthorombic-hexagonal transition. An orthorhombic structure represents a prism-like crystal structure with three unequal edges and internal angles, whereas a hexagonal structure resembles a hexagon with six equal edges. The tensile test was used to reveal the effect of drawn ratios on performance and it was revealed that with the increase in drawn ratio, the mechanical strength would increase by a maximum of 322.71%. Simultaneously, this thesis also focuses on investigating the enhancement of interface properties in UHMWPE fiber/epoxy composites.There are numerous surface treatment methods used to improve the coaction between fibers and composite materials, chemical etching and corona discharge are two commonly used methods to enhance the fiber- epoxy interaction. In this thesis study, the optimum corona discharge result was revealed by experiments performed at different voltage and time parameters. Then, the obtained results from corona discharge method were compared with the results obtained when the surface was modified via chemical etching, and it was seen that hydroxyl and carboxyl groups were formed on the surface more effectively in the chemical etching method. Glutaraldehyde, which is used as a cross-linking agent in chemical etching method, can form bonds with OH functional groups due to its chemical structure. Thus, the hydroxyl groups formed on the UHMWPE fibers become able to cross-link with the hydroxyl groups in the epoxy. Tests have shown an increase in both mechanical performance and adhesion.
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ÖgeThe synthesis and characterization of a novel flame retardant containing rigid polyurethane foam(Graduate School, 2024-07-04)Rigid polyurethane foams are one of the most preferred thermal insulation materials due to their excellent thermal insulation properties, mechanical strength, lightness, and applicability. They are used in various fields from household appliances to pipes, cladding, and insulated panels, and are commonly encountered in daily life. However, these materials pose a risk to human life and health due to their weak characteristic of being easily flammable and capable of intensifying fires. This risk has created a need for flame retardant materials. Flame retardants are added to polyurethane to prevent the flames from rapidly intensifying in the event of a fire, providing people with an escape time. Traditional flame retardants contained halogens such as bromine and chlorine, but their use has been restricted due to the release of toxic gases during a fire. As a result, there has been a need for alternative flame retardants with different chemical structures. Currently, commonly used flame retardants include phosphorus-based compounds such as tris(2-chloroethyl) phosphate and triphenyl phosphate; phosphonates such as dimethyl propyl phosphonate; ammonium polyphosphate (APP) and DOPO derivatives like phosphaphenanthrene oxide; nitrogen-based compounds such as melamine, melamine cyanurate, and melamine polyphosphate; polymeric silicone derivatives; and inorganic flame retardants like magnesium hydroxide and aluminum trihydroxide. This thesis was carried out in two stages: the synthesis of a flame retardant containing fluorine and nitrogen, and the addition of the flame retardant to rigid polyurethane foam. The synthesis process was carried out in three stages, successfully synthesizing a fluorine-containing, hydroxyl-terminated compound with a triazole structure through a copper-catalyzed azide-alkyne cycloaddition reaction, an example of click chemistry. Techniques such as fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies were used to elucidate the structural properties of the resulting compound. The flame retardant, incorporated into the rigid polyurethane formulation by mechanically mixing in various percentages, was aimed to react with isocyanates, through its OH groups as a polyol, which are the components of polyurethane, thus exhibiting chemical flame retardant functionality. Consequently, the structural properties of the RPUF samples were examined using techniques such as FTIR, thermal and flammability properties with cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA), and thermal conductivity meter, and morphological properties with scanning electron microscopy (SEM). The impact of the flame retardant on the mechanical properties was investigated through compression testing and foam density measurements of the RPUF samples. The hydrophobic contribution of the flame retardant to the foam samples due to its fluorine content was measured with a contact angle meter. All analyses were carried out on foam samples containing no flame retardant and those containing 5%, 10%, and 15% flame retardant. Test results show significant improvement in the flame retardancy of rigid polyurethane foam with enhanced LOI values and reduced peak heat release rates. Additionally, it was observed that the flame retardant successfully bonded chemically to the foam structure, did not deteriorate its mechanical properties and cell structure, maintained excellent thermal insulation, and increased contact angle values imparted hydrophobicity due to its fluorine content. This thesis demonstrates the potential of nitrogen and fluorine-containing flame retardants for providing superior fire protection, indicating that they are promising candidates for future applications in fire-resistant materials.