Crystallization, properties, and crystal and nanoscale morphology of PET-clay nanocomposites

The crystallization process and crystal morphology of poly(ethylene terepha thalate) (PET)-clay nanoscale composites prepared by intercalation, followe d by in-situ polymerization, have been investigated by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic scannin g calorimetry (DSC), and X-ray techniques, together with mechanical methods . Results of the nonisothermal crystallization dynamics show that the nanoc omposites of PET (Nano-PET) have 3 times greater crystallization rate than that of pure PET. The thermal properties of Nano-PET showed heat distortion temperature (HDT) 20-50 degrees C higher than the pure PET, while with a c lay content of 5%, the modulus of Nano-PET is as much as 3 times that of pu re PET. Statistical results of particle distribution show that the average nanoscale size ranges from 10 to 100 nm. The particles are homogenously dis tributed with their size percentages in normal distribution. The agglomerat ed particles are 4% or so with some particles size in the micrometer scale. The morphology of exfoliated clay particles are in a diordered state, in w hich the morphology of the PET spherulitics are not easy to detect in most of microdomains compared with the pure PET. The molecular chains intercalat ed in the interlamellae of clay are confined to some extent, which will exp lain the narrow distribution of the Nano-PET molecular weight. The stripe-b elt morphology of the intercalated clay show that polymer PET molecular cha ins are intercalated into the enlarged interlamellar space. (C) 1999 John W iley & Sons, Inc.