Journal of Polymer Science Part B: Polymer Physics, Vol.36, No.7, 1219-1225, 1998
Rapid crystallization and thermoreversible gelation of poly(ethylene terephthalate) in polymer/oligomer binary system
Poly(ethylene terephthalate)(PET) Tvas rapidly crystallized through thermoreversible gelation in a liquid ethylene glycol oligomer or in epoxy resin. The solutions formed gel rapidly on cooling. Polarized light microscopy and small-angle light scattering showed that these gels contain large, regular I)ET spherulites. The gels may be formed by two consecutive processes : the phase separation and crystallization, and gelation by formation of a three-dimensional PET network in the oligomer solvents, where the nodes of the network are PET spherulites. The crystallinity of PET recovered from polymer/oligomer gels is near 72% measured by wide-angle X-ray diffraction method, which is about 20% higher than PET samples crystallized by solution crystallization in small molecule 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; fluoresence and Raman spectroscopic studies indicated that PET recovered 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-extracted PET from a 0.5 wt % solution in phenol.
Keywords:INDUCED PHASE-SEPARATION;FLUORESCENCE SPECTROSCOPY;CONCENTRATION-DEPENDENCE;ISOTACTIC POLYSTYRENE;POLY(ETHYLENE-TEREPHTHALATE);POLYMERS;CRYSTALLINITY;DYNAMICS