Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Publisher: search.filters.publisher.John Wiley and Sons Inc.Subject: search.filters.subject.Crystallization

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  • Article
    Citation - WoS: 19
    Citation - Scopus: 20
    Isothermal Crystallization Kinetics and Mechanical Properties of Polycaprolactone Composites With Zinc Oxide, Oleic Acid, and Glycerol Monooleate
    (John Wiley and Sons Inc., 2013) Alp, Burcu; Cesur, Serap
    The isothermal crystallization and mechanical behavior of polycaprolactone (PCL) with zinc oxide (ZnO) with oleic acid and glycerol monooleate (GMO) were studied. Theoretical melting points calculated by the Flory-Huggins and Thompson-Gibbs models were thoroughly compared with differential scanning calorimetry experimental observations. The isothermal crystallization kinetic parameters by Avrami analysis showed that crystallization was controlled by nucleation, crystal growth was spherical, and the nucleation type changed between thermal and athermal nucleation. X-ray diffraction showed that when the additives were used together both the crystal thickness and the degree of crystallinity increased. A multiple-response regression analysis was made with the ZnO, oleic acid, and GMO concentrations as variables and the crystallinity as output. Interaction parameters by the Pukanzky model were calculated from the tensile strength at the yield point and indicated that the addition of oleic acid or GMO improved the interface between the ZnO particles and PCL.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 18
    Crystallization of Poly(vinyl Alcohol) During Solvent Removal: Infrared Characterization and Mathematical Modeling
    (John Wiley and Sons Inc., 2007) Wong, Sim-Siong; Alsoy Altınkaya, Sacide; Mallapragada, Surya K.
    Crystallization of semicrystalline polymer films during drying has a significant effect on the rate of solvent removal. Understanding and controlling the crystallization kinetics is important in controlling residual solvent levels and drying kinetics. The degree of crystallinity of the poly(vinyl alcohol) films during multicomponent drying was investigated using Fourier transform infrared spectroscopy (FTIR). The 1141 cm-1 band is sensitive to the degree of crystallinity of the polymer and the growth of intensity of this band was monitored as drying progressed. The results from the FTIR studies were comparable to the results obtained from differential scanning calorimetry. Studies were conducted to test the effect of initial solvent composition (water-methanol mixture), drying temperature, and polymer molecular weight on the rate of crystallization and the final crystallinity of the films. An increase in initial methanol composition increased the crystallization rate but did not affect the final degree of crystallinity. An increase in drying temperature and decrease in polymer molecular weight increased the rate of crystallization as well as the final degree of crystallinity. Based on the experimental data, rate constants for crystallization kinetics were extracted from our previously developed model based on free volume theory. The experimental data and the simulation results showed good agreement. The ability of the free volume theory to illustrate the crystallization behavior validated the model and improved its capability.
  • Article
    Citation - WoS: 42
    Citation - Scopus: 42
    Natural Zeolite Polypropylene Composite Film Preparation and Characterization
    (John Wiley and Sons Inc., 2001) Özmıhçı, Filiz; Balköse, Devrim; Ülkü, Semra
    In this research, the preparation and characterization of polypropylene (PP) and natural zeolite composites were studied. Natural zeolite mined in Gördes, Turkey was used as an alternative filler to CaCO3. Films were prepared by the extrusion of PP, and surface-modified zeolite was made by polyethylene glycol 4000 with 2-4% zeolite. Zeolite-filled composites had densities between 0.73 and 0.83 g/cm3 and had void fractions of 0.07-0.20. Although the permeability of water vapour through 2% zeolite-filled composites was very small, 4% zeolite-filled films had very high permeabilities. The yield stresses of 2-4% zeolite-containing films were around 26-27 N/mm2 and were lower than that of PP, which indicated no adhesion between PP and zeolite. The effect of zeolite on the thermal degradation behaviour in air and in a N2 atmosphere was also studied. In air, zeolites did not cause the oxidation of PP. In a N2 atmosphere, although the start of the thermal degradation of PP was retarded by zeolite, composites degraded at a faster rate than PP once the degradation started. At a processing temperature of 200°C, zeolites had no effect on the degradation of PP.