This work prepared poly(ethylene terephthalate)/clay (PET/clay), PET/poly(ethylene glycol-co-1,3/1,4-cyclohexanedimethanol terephthalate) (PET/PETG), and PET/PETG/clay nanocomposites via the twin-screw extrusion process. The organoclay in PET and PET/PETG matrices are in homogeneous dispersion, and the spacing distances between the platelets in the PET/clay and PET/ PETG/clay nanocomposites are larger than 33.9 Å . Differential scanning calorimetry (DSC) and polarizing optical microscope (POM) analyses showed that the inclusion of organoclay significantly increased the crystallinities and melting temperatures of PET/clay and PET/PETG/clay nanocomposites with less time required to undergo isothermal crystallization. These findings imply the occurrence of heterogeneous nucleation. However, amorphous PETG substantially decreased the crystallinity of the crystallizable units of PET. Morphologically, the inclusion of organoclay drove the crystallites of PET from a spherulite with more perfection and less dimension to a larger spherulite. This process was extended from PET/clay to PET/PETG/clay in which the crystallites propagated in twodimensional and disc-like morphology. However, blending PET with amorphous PETG imparted the larger crystallites with relatively distorted Maltese-cross patterns. INTRODUCTIONPET is a semicrystalline engineering thermoplastic and widely used in textiles, automobiles, and food and beverage packaging. Apart from its high-performance mechanical properties and film clarity, the excellent gas-barrier property for reducing air permeability makes PET polymer an outstanding and unique material in food and beverage packaging applications. Understandably, PET has a worldwide consumption, second only to polyolefines. Recently, several researchers have reported that the incorporation of clay increases the gas barrier properties of PET/clay nanocomposites. 1-5 Nevertheless, the crystallization rate of PET/clay nanocomposites exceeds that of PET, in which the clay is believed to act as a nucleating agent. 6-17 PET/clay nanocomposites are generally opaque due to high crystallinity arisen by the inclusion of clay, and under this condition the nanocomposites can no longer be used in food and beverage packaging.In contrast to semicrystalline PET polymers, PETG is an amorphous thermoplastic of the commercial PET family, with physi-cal properties similar to PET. 18,19 In our previous study, we demonstrated that the amorphous nature of PETG would be unaffected by the inclusion of clay. 20 Instead, PETG has been found to form a miscible blend with PET. 21 Papadopoulou and Kalfoglou reported that the PET/PETG blend has a single endothermic peak in both T g (93.3 C) and T m (235.0 C) at a mixing ratio of 50/50 under the second heating run, indicating that this blend has good compatibility. 21 Moreover, the same researchers reported that PETG combines good toughness, even at low temperatures, with film clarity and melt strength. To improve the barrier properties of PETG polymer while maintaining its transparenc...
The isothermal crystallization behavior of nano‐alumina particle‐filled poly(ether ether ketone) (PEEK) composites has been investigated using differential scanning calorimeter. The results show that all the neat PEEK and nano‐alumina‐filled PEEK composites exhibit the double‐melting behavior under isothermal crystallization. The peak crystallization times (τp) for all the neat PEEK and PEEK/aluminum oxide (Al2O3) composites increase with increasing crystallization temperature. Moreover, the crystallinity of the PEEK/Al2O3 composite with 7.5 wt % nano‐filler content reached the maximum value of 44.8% at 290°C, higher than that of the neat PEEK polymer. From the lower value in τp and higher value in Xc for the PEEK/Al2O3 composites, the inclusion of the nano‐alumina into the PEEK matrix favored the occurrence of heterogeneous nucleation. The Avrami exponents n of all the neat PEEK and PEEK/Al2O3 composites ranged from 2 to 3, and the n values for PEEK/Al2O3 composites were slightly higher than that of the neat PEEK polymer, indicating that the inclusion of the nano‐filler made the crystallization mechanism more complex. However, the growth rate of crystallization was lowered as the nano‐ filler was introduced, and the decrease in growth rate reduced the grain size of the PEEK spherulites because of the lowering of molecule mobility during isothermal crystallization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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