Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 14Citation - Scopus: 17The Effects of Natural Zeolite and Silane Coupling Agents on Melting and Crystallization Behaviour of Polypropylene(Springer Verlag, 2008) Başalp, Dildare; Tıhmınlıoğlu, FundaThe thermal characterization of polypropylene (PP) composites containing untreated and treated zeolite with different silane coupling agents was carried out using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to investigate the effects of natural zeolite and surface modifiers on melting, crystallization and degradation behaviour of PP. 3- aminopropyltriethoxysilane (AMPTES), methyltriethoxysilane (MTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used as surface modifiers at four different concentrations (0.5-2.0 mass%). Thermal analyses indicated that silane treatment and 2-6 mass% zeolite addition have no significant effect on the melting and degradation temperatures of the composites. The crystallization temperatures of the composites were increased due to the nucleating effect of the zeolite. The influence of the modifiers on the interactions between PP and zeolite was determined by the activities of untreated and treated zeolite. The maximum interactions leading to good adhesion were observed in the AMPTES treated composites. Also, non-isothermal crystallization kinetics of the composites was analyzed using Avrami and Kissinger models.Article Citation - WoS: 10Citation - Scopus: 10Multi-Zone Drying Schemes for Lowering the Residual Solvent Content During Multi-Component Drying of Semicrystalline Polymers(Taylor and Francis Ltd., 2007) Wong, Sim-Siong; Alsoy Altınkaya, Sacide; Mallapragada, Surya K.The development of a glassy skin in multicomponent semicrystalline polymer systems limits the diffusion of solvents out of the system and increases residual solvent levels. Based on the results of a mathematical model that we had previously developed, we have proposed a multi-zone drying scheme aimed at lowering the residual solvent levels by taking into account the effect of interactions between the various solvents as predicted by the model. This article focuses on the application of this model to develop optimal drying schemes and to verify the effectiveness of these predictions using experimental techniques. The mathematical model developed previously to study the diffusion of multiple solvents and changes in the crystallinity of semicrystalline polymer systems during drying incorporates many features including Vrentas-Duda diffusion theory, solvent-induced crystallization kinetics, as well as glass transition effects and skinning of the film. The multi-zone drying system was developed by varying the drying temperature in each zone as well as changing the partial pressure of individual solvents during the drying process. The effectiveness of the multi-zone drying schemes predicted by the model was validated experimentally using thermogravimetric methods. The polymer-solvent system chosen was a poly(vinyl alcohol)-water-methanol system. Our experimental data suggested that the multi-zone drying schemes were superior to a single-zone drying system through direct comparison. Further examination of the mathematical model yielded individual solvent profiles and these data reaffirmed our conclusions that a multi-zone drying scheme has the ability to reduce the effect of solvent trapping and thus lower the overall residual solvent content.Article Citation - WoS: 46Citation - Scopus: 48Drying of Semicrystalline Polymers: Mathematical Modeling and Experimental Characterization of Poly(vinyl Alcohol) Films(Elsevier Ltd., 2004) Wong, Sim-Siong; Alsoy Altınkaya, Sacide; Mallapragada, Surya K.A mathematical model was developed to predict the drying mechanism of semicrystalline polymers involving multiple solvents. Since drying of semicrystalline polymers can be accompanied by changes in polymer degree of crystallinity, the model integrates crystallization kinetics and the Vrentas-Duda diffusion model to provide a better understanding of the mechanism. The model considers the effect of external conditions such as temperature, film shrinkage and diffusion and evaporation of multiple solvents during drying. Poly(vinyl alcohol) (PVA)/water/methanol was chosen as a test system. The drying kinetics of PVA films swollen in water and methanol were investigated using gravimetric techniques. The model predicts that higher temperatures, lower film thicknesses and lower methanol to water ratios increase the drying rate. The model predictions were compared with experimental data and showed good agreement.