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    Investigations of the Nucleating Agent Effects on Polypropylene of Pumice from Three Distinct Areas in Türkiye
    (Mdpi, 2025) Ozdemir, Yasin; Atagur, Metehan; Sen, Ibrahim; Sever, Kutlay
    This study investigates the mechanical and thermal properties of polypropylene (PP) composites incorporating pumice, a naturally occurring porous volcanic rock with high SiO2 content, sourced from three regions in T & uuml;rkiye (Nev & scedil;ehir, Ala & ccedil;at & imath;, and K & uuml;tahya). Pumice was processed to particle sizes below 10 microns to maximize nucleating effectiveness, and composites were fabricated by melt compounding. The distinct mineralogical composition, porosity, and surface chemistry of the pumice samples enabled systematic evaluation of how regional variations influence crystallization and mechanical performance. A multi-analytical characterization approach, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and standardized mechanical tests (tensile, flexural, and impact), was applied. Results revealed that Ala & ccedil;at & imath; pumice at 0.1 wt% increased the impact strength of PP by about 11%, while maintaining stiffness. This demonstrates that pumice, unlike conventional fillers, can simultaneously enhance toughness and rigidity. Thermal analysis confirmed improved stability, with higher degradation onset and maximum decomposition temperatures observed in pumice-filled PP. DSC results indicated that certain pumice loadings promoted nucleation and increased crystallinity, while excessive amounts disrupted chain packing. SEM examinations confirmed uniform dispersion at low loadings, with agglomeration at higher levels reducing impact resistance. This work provides the first systematic demonstration of pumice powders as effective nucleating agents in PP, combining regional mineralogical diversity with measurable performance benefits. These findings indicate that pumice can serve as a sustainable, low-cost alternative to conventional nucleating agents, with potential applications in polymer components requiring improved toughness and thermal stability.
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    Manufacturing and Characterization of Three Modified Vegetable Oil-Added Polylactic Acid Composites
    (Wiley, 2024) Sen, Ibrahim; Atagur, Metehan; Tuna, Sibel; Eroglu, Murat; Kurtlu, Meral Akkoyun; Sever, Kutlay
    Polylactic acid (PLA) was modified with three types of modified vegetable oils (MVOs), which are the epoxidized soybean oil (ESBO), maleinized sunflower oil (MSO), and maleinized olive oil (MOO), at different weight fractions. A corotating twin screw extruder was used to produce composite materials by the melt-mixing process. The effect of MVO content, from 2.5% to 10%, on the morphology, mechanical properties, density, and water absorption was investigated in detail. The addition of ESBO and maleinized vegetable oils leads to a slight decrease in the density of PLA from 1.252 to 1.231 g/cm3. As the concentration of MVO in PLA increases, the amount of water absorption also increases, and the highest water absorption value was observed in P10MSO. The FTIR spectra of all concentrations of the MOO and MSO have two peaks at 1781 and 1861 cm-1, attributed to the C=O stretching which is related to maleic acid copolymerization. In general, the elastic modulus (EM) was slightly changed by the addition of MVOs to PLA, while the tensile strength (TS) decreased. Due to the plasticizing effect of MVOs, an increase in the Izod impact strength was obtained.