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    Effect of silane-modification of diatomite on its composites with thermoplastic polyurethane
    (Elsevier Science Sa, 2020) Kucuk, Fatma; Sismanoglu, Sedef; Kanbur, Yasin; Tayfun, Umit
    Diatomite (KG) surface was modified by four different silane coupling agents having amino, epoxy, triamine and octyl functional groups for enhancement of interfacial adhesion between thermoplastic polyurethane (TPU) and diatomite. EDX and FTIR spectroscopy techniques were used to evaluate the surface functionalities of modified and neat KG samples. TPU/KG composites were fabricated using melt-compounding process. Mechanical, thermo-mechanical, thermal, melt-flow and morphological properties of composites were reported. Mechanical tests revealed that tensile strength and hardness of TPU extended to higher levels while its flexibility was retained after KG additions. Epoxy-silane modified KG exhibited the highest results in the case of mechanical properties. Glass transition temperature of TPU shifted to higher values by the additions of modified KG. Thermal stability of TPU raised by KG inclusions regardless of modification type. Modified KG containing composites yield lower MFI values with respect to neat KG. Enhancement of interfacial adhesion between TPU and KG phases was confirmed by SEM micrographs of composites in which silane-modified KG surfaces were covered by TPU matrix. Silane modifiers involving amine and epoxy groups led to significant improvement in properties of KG-filled TPU composites. Epoxy-based silane displayed the highest performances thanks to strong interfacial interactions between epoxy functional group and isocyanate segment of TPU.
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    Optimization of mechanical, thermo-mechanical, melt-flow and thermal performance of TPU green composites by diatomaceous earth content
    (Elsevier, 2021) Kucuk, Fatma; Sismanoglu, Sedef; Kanbur, Yasin; Tayfun, Umit
    In the present paper the effect of the diatomite, also known as diatomaceous earth and kiesel guhr (KG), content on mechanical, thermo-mechanical, melt-flow and thermal performance of thermoplastic polyurethane-based composites was investigated. Composites were fabricated by melt blending method with 10, 20, 30 and 40% filling ratios of KG. and injection molded test samples were characterized using tensile, hardness, dynamic mechanical analysis (DMA), melt flow index (MFI), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) analysis. According to test results, KG inclusions effect mechanical, thermal and morphological properties of composites positively up to 30% KG content. Further addition of KG caused remarkable reductions in related properties. Tensile strength of unfilled TPU exhibited increasing trend and elongation showed no obvious difference after KG loadings. TPU/KG composites yield relatively higher MFI values with respect to unfilled TPU. Glass transition temperature of TPU shifted to 6 points higher value by the help of KG incorporation. TGA findings revealed that KG additions caused improvement for thermal stability of TPU. Homogeneous dispersion of KG particles for their lower content, whereas agglomorate formations for higher loading level of KG were confirmed by SEM micrographs. TPU composite containing 10% KG showed the highest results among samples.