LEE- Malzeme Bilimi ve Mühendisliği Lisansüstü Programı

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http://hdl.handle.net/11527/19374

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Konu "atık değerlendirme" ile LEE- Malzeme Bilimi ve Mühendisliği Lisansüstü Programı'a göz atma
  • Öge
    Attempts to re-evaluate waste thermoplastic polyurethane (TPU)
    (Graduate School, 2025-01-16) Yanık, Simay ; Nofar, Mohammadreza ; 521211022 ; Materials Science and Engineering
    Polymers' excellent mechanical and thermal qualities, lightweight nature, and economical manufacturing have made them essential materials in many different sectors. However, there are major environmental issues with waste management and large-scale polymer production, which highlights the need for sustainable recycling solutions. Thermoplastic polyurethanes (TPUs), which are widely used in industries including consumer goods, automotive, and medicine, are known for their flexibility, toughness, and chemical resistance. In order to encourage sustainable material development, this study aims to enhance the revaluation of TPU waste through chemical modification and blending procedures. The environmental problems caused by polymeric waste are highlighted in this study of the literature, especially in the case of TPU, which has been widely used in the consumer goods, automotive, and medical sectors. TPU is a good option for recycling because of its thermoplastic characteristics, mechanical strength, and durability. However, the process is made more difficult by its structural complexity and the presence of additives. Studies has investigated polymer blending and chemical modification as approaches to enhance the properties of TPU and make recycling less challenging. The rheological, mechanical, and thermal properties of TPU are enhanced via chemical modification. Through a variety of processes, additives such diisocyanates (polymerized-methylene diphenyl diisocyanate (PMDI), and hexamethylene diisocyanate (HDI)), Joncryl ADR 4468, pyromellitic dianhydride (PMDA), and other different additives have an impact on the properties of TPU. Waste of TPU could also have effectively revaluate through blending it with polymers including polylactic acid (PLA), polyamide (PA), polymethyl methacrylate (PMMA), and polybutylene terephthalate (PBT). This method improves mechanical properties including toughness, flexibility, and impact resistance while addressing PLA's shortcomings, such as brittleness, low melt strength, and slow degradation. However, compatibility problems with PLA/TPU blends can result in phase separation as well as limitations. Compatibilizers such as Joncryl optimize mechanical and thermal qualities by enhancing phase compatibility and blend morphology. The objective of this thesis is to develop sustainable materials with improved mechanical, thermal, morphological, and rheological properties by improving the reutilization of TPU waste through chemical modification and blending techniques. Due to TPU's great resistance to degradation and growing environmental concerns about its recycling and disposal, improved methods are required to increase its reusability. Through the chemical modification of TPU with different additives and also blending the waste TPU with biodegradable polymers like PLA, this work aims to address these problems. The experimental process has been divided into two parts: the chemical modification and blending. TPU wastes have been melt processed with additives (PMDI, HDI, Joncryl ADR 4468, and PMDA) at 0.5% and 1% by weight for five minutes at 200°C and 100 rpm in an internal melt mixer. Rheological, mechanical, thermal, and properties of the samples were determined using small amplitude oscillatory shear (SAOS) rheometer, tensile and hardness tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). PLA/TPU blends were made with 20% waste TPU and 80% PLA in a twin screw extruder. Joncryl was utilized as a compatibilizer in certain samples. Mechanical, thermal, and morphological properties of the samples were investigated using tensile, impact, and hardness tests, DSC, TGA, and scanning electron microscopy (SEM). Chemical modification study findings shown significant increases in TPU properties depending on the type and concentration of additions. particularly when diisocyanates are incorporated, resulting in improved mechanical performance (tensile strength and elongation at break) and melt strength (complex viscosity) while preserving thermal stability. However, PMDA-modified TPU resulted in lower mechanical performance because to hydrolysis-induced degradation. This finding highlights the potential of the modifications to enhance material performance without compromising its fundamental characteristics. Experiments carried out in the second stage of the study indicated that, the use of waste TPU contributed to improving the disadvantageous properties of PLA. Based on the results of various mechanical analyses, the structure obtained by blending PLA and TPU exhibited a decrease in tensile strength due to the immiscibility between PLA and TPU. However, the presence of TPU led to a more ductile structure, reflected by an increase in elongation at break values, while hardness values decreased. Additionally, TPU enhanced the impact resistance properties of PLA. The incorporation of Joncryl ADR 4468 as a compatibilizer improved phase compatibility, thereby enhancing the mechanical properties. Blend structure created by pre-blending TPU with Joncryl (PLA/(TPU/J)*) resulted in only a slight increase in tensile strength and modulus values. SEM analysis revealed that phase separation occurred due to the immiscibility of PLA and TPU, with TPU appearing as droplets inside the PLA matrix. The addition of Joncryl increased phase compatibility, resulting in finer and more uniform microstructures by interacting with PLA and TPU to lower interfacial tension and increase viscosity by branching in the PLA matrix. Stronger interphase bonding and a more stable structure were confirmed in PLA/(TPU/J)* blends. The microstructure was further improved by pre-blending TPU with Joncryl, which improved its dispersion inside the blend. The presence of TPU improved PLA's thermal stability and processability by increasing the degree of crystallization while decreasing its total crystallinity, according to thermal analysis. Tg of PLA was lowered by TPU's plasticizing effect, which may reduce brittleness. Joncryl enhances the overall performance of the blend and increases the maximum degradation temperatures, especially when blended with TPU before that, which greatly increases thermal stability. This study emphasizes the possibilities of chemical modification and blending methods for tackling TPU waste recycling concerns. While the incorporation of additives enhances the rheological and mechanical property of TPU, blending it with PLA tackles PLA's limitations, and the two methods promote the revaluation of waste TPU. The findings emphasize the importance of optimizing process parameters, selecting suitable materials, and evaluating alternating additives for enhanced performance. These efforts contribute to the development of sustainable materials, reduction of polymer waste, and promotion of a circular economy.