Yazar "Wis, Abdulmounem Alchekh" seçeneğine göre listele

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    Enhanced crystallinity through melt annealing of thermoplastic polyurethanes
    (John wiley and sons inc, 2025) Akkoyun, Bahar Durak; Wis, Abdulmounem Alchekh; Yıldırım, Rümeysa; Makal, Ümit; Özkoç, Güralp; Kodal, Mehmet
    This study evaluated the influence of melt annealing on thermoplastic polyurethane (TPU) synthesized via reactive extrusion, aiming to enhance TPU melt crystallization behavior. The melt annealing process involved reprocessing the polymer in a twin-screw extruder, leveraging a novel approach to manipulating crystallization behavior by optimizing melt annealing conditions to activate microphase separation. Differential scanning calorimetry analysis indicated increased nucleation density and a shift in peak crystallization temperature to higher values during cooling. Phase morphology was examined using scanning electron microscopy, while gel permeation chromatography was utilized to assess molecular weight changes. X-ray diffraction provided insights into TPU microstructural modifications, and mechanical properties were evaluated via tensile tests. Fourier-transform infrared spectroscopy was employed to analyze annealing-induced changes in the hard segment structure and interpolymer bonding. The findings demonstrated that annealing enhances mechanical properties, promotes microphase separation, and increases the energy available for movement and realignment of hard segments, thereby improving TPU's thermal stability. Precise control of annealing temperature was critical to prevent adverse effects on polymer morphology or molecular weight reduction. Annealing at 210 degrees C yielded the highest degree of crystallinity, optimizing mechanical properties and thermal stability.
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    A review on polyhedral oligomeric silsesquioxanes as a new multipurpose nanohybrid additive for poly(lactic acid) and poly(lactic acid) hybrid composites
    (WILEY, 2022) Ullah, Muhammad Saeed; Yazıcı, Nazlı; Wis, Abdulmounem Alchekh; Özkoç, Güralp; Kodal, Mehmet
    Abstract The production of petroleum-based polymers in huge amounts is perilous for our ecosystem and oil reserves. The use of biodegradable polymers instead of synthetic polymers for various commodity, engineering, and biomedical applications remains the overriding concern of the researchers in last decades. Although poly(lactic acid) (PLA) is considered to be the most befitting substitute for conventional petroleum-based products because of its superlative mechanical properties, material & processing cost, and non-toxicity, they have some consequential limitations for various applications because of their slow rate of crystallization, low thermal stability, high brittleness, and low toughness. To overwhelm these deficiencies during the last two decades, researchers have developed various techniques to tailor the properties of PLA, that is, blending with other polymers or using additives such as nanofillers. Among all the nanofillers, for example, carbon nanotubes and organoclays, polyhedral oligomeric silsesquioxanes (POSS) was found the most promising nanofiller because of its organic and inorganic nanostructure and fine dispersion into PLA matrix. This article reviews all the investigations relevant to POSS incorporation into PLA or blends of PLA with other polymers to compare the mechanical, morphological, and physical properties of the ameliorated composites and the neat PLA.