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In this study, cold and melt crystallization behaviors of amorphous poly(ethylene terephthalate) (PET)/clay nanocomposites were investigated. Two nanocomposite samples with the same amount of inorganic content were prepared by melt processing using natural montmorillonite (Na‐MMT) and organo‐modified montmorillonite (org‐MMT). Depending on the clay structure, clay dispersion into PET and crystallization behavior of the samples were studied using X‐ray diffraction and differential scanning calorimetry methods, respectively. Effects of clay structure and organic groups between clay layers in org‐MMT on the melt crystallization kinetics of the samples were analyzed with various kinetic models, namely, the Ozawa, Avrami modified by Jeziorny, and Liu‐Mo. Crystallization activation energies of the samples were also determined by the Kissinger and Augis–Bennett models. Exfoliated structures were obtained in the nanocomposite samples prepared with both the Na‐MMT and org‐MMT. From the kinetics study, it was found that the melt‐crystallization rate of the sample prepared with the Na‐MMT was higher than that prepared with the org‐MMT at a given cooling rate. It can be concluded that organic ammonium groups in the org‐MMT decelerate the crystallization rate of PET chains possibly by affecting the chain diffusion and folding. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

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In this study, melt-crystallization behaviors of poly(butylene terephthalate) (PBT) composites including different types of inorganic fillers were investigated. Composite samples having 5 wt % of fillers were prepared by melt processing in a twin screw extruder using commercial grades of calcite (CA), halloysite (HL), and organomontmorillonite (OM) as filler. Depending on the filler type and geometry, crystallization kinetics of the samples was studied by differential scanning calorimetry (DSC) methods. Effect of filler type on the nonisothermal meltcrystallization kinetics of the PBT was analyzed with various kinetic models, namely, the Ozawa, Avrami modified by Jeziorny and Liu-Mo. Crystallization activation energies of the samples were also determined by the Kissinger, Takhor, and Augis-Bennett models. From the kinetics study, it was found that the melt-crystallization rates of the samples including CA and HL-nanotube were higher than PBT at a given cooling rate. On the other hand, it was also found that organo-montmorillonite reduced the melt-crystallization rate of PBT. It can be concluded that organic ammonium groups in the OM decelerate the crystallization rate of PBT chains possibly due to affecting the chain diffusion through growing crystal face and folding. This study shows that introducing organically modified alumina-silicate layers into the PBT-based composites could significantly reduce the production rate of the injection molded parts during the processing operations. V C 2011Wiley Periodicals, Inc. J Appl Polym Sci 123: [77][78][79][80][81][82][83][84][85][86][87][88][89][90][91] 2012

In this study, nonisothermal crystallization kinetics of glass fiber (GF) and clay-type mineral (MN)-reinforced polyamide-6 (PA6) composites prepared in a twin screw extruder were investigated by differential scanning calorimetry method in the presence and absence of an organic nucleating agent (NA). Kinetic parameters for the nonisothermal melt-crystallization process of samples were determined with several models namely Ozawa, Avrami, Jeziorny, and Liu-Mo. Crystallization rate parameters of the samples and nucleation activity of the fillers and additives were also calculated by the models suggested by Zhang and Dobreva and Gutzow, respectively. Crystallization activation energies of the samples were determined by the Kissinger model. It was found that the MN filler accelerates dramatically the crystallization rate of PA6 even without a NA. Small amount of NA also has a significant acceleration effect on the crystallization rate of PA6 composites. The rate acceleration effect of NA was found to be more pronounced in the composite sample reinforced with GF. Based on the kinetic study using of GF as major filler and small amount of clay-like MN in the PA6 composites could improve the mechanical properties and crystallization rate of injection-molded parts. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E268-E281, 2012

In this study, microstructural features and physical properties of thermoplastic polyurethane (TPU)/organoclay nanocomposites films prepared via melt blending (MB) and solution mixing (SM) methods were investigated in detail. Amount of organoclay into the composition varied in the range of 2 and 8 wt%. Microstructural properties of samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. It was found that the organoclay layers exhibited better dispersion, exfoliated, and semi-exfoliated structure in the MB samples than the SM counterparts. Viscoelastic properties of samples were also studied by measuring the rheological behaviors of bulk samples in an oscillatory rheometer in the melt state and measuring of the time-dependent nonlinear creep behaviors of film samples in a dynamic mechanical analyzer in the solid state. Gas and water vapor permeability (WVP) values of nanocomposite films were measured. Based on the melt rheology measurements, it was found that the MB samples showed characteristic solid-like behavior and higher improvement in storage modulus at low-frequency region. Creep behaviors of samples were also quantified with the four-element Burger model. It was found that the introducing of organoclay into the composition via MB method yielded more improvement in the creep resistance, gas, and WVP values of films than the SM counterparts, possibly due to the better dispersion of organoclay layers into the TPU structure. Based on the improvement in permeability and mechanical properties of the samples and also SEM and TEM observations, the average aspect ratio value ( Af) of organoclay stacks was estimated in the range of 15–20 for the MB samples.

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