RAPID CRYSTALLIZATION AND THERMOREVERSIBLE GELATION OF POLY(ETHYLENE-TEREPHTHALATE) IN POLYMER OLIGOMER BINARY-SYSTEM/

Poly(ethylene terephthalate)(PET) Tvas rapidly crystallized through th ermoreversible gelation in a liquid ethylene glycol oligomer or in epo xy resin. The solutions formed gel rapidly on cooling. Polarized light microscopy and small-angle light scattering showed that these gels co ntain large, regular I)ET spherulites. The gels may be formed by two c onsecutive processes: the phase separation and crystallization, and ge lation by formation of a three-dimensional PET network in the oligomer solvents, where the nodes of the network are PET spherulites. The cry stallinity of PET recovered from polymer/oligomer gels is near 72% mea sured by wide-angle X-ray diffraction method, which is about 20% highe r than PET samples crystallized by solution crystallization in small m olecule solvent, high temperature annealing, and stretching techniques . It takes only a few minutes to form the highly crystalline phase PET in the PET/oligomer system, and the crystallinity of the dried gel is independent of the concentration of the original solution. Excimer; f luoresence and Raman spectroscopic studies indicated that PET recovere d from tie gels are in an ordered state with few chain entanglements. The entanglement density of the recovered PET recovered from a 20 wt % solution in ethylene glycol oligomer is as low as that of freeze-extr acted PET from a 0.5 wt % solution in phenol. (C) 1998 John Wiley & So ns. Inc.