No abstract

SynopsisThe diffusion of vapors and liquids which induce crystallization in initially amorphous, unoriented poly(ethy1ene terephthalate) (PET) films was studied. It was determined that these vapors and liquids penetrate the polymer as distinct fronts, and the kinetics of this penetration and the weight uptake kinetics both follow apparent Fickian behavior. Distinct cavitation advanced into the polymer a t the penetrant front-dry polymer interface in certain PET-liquid systems, and phenomenological explanations of its existence and of the general diffusion process observed are offered. Finally, the diffusion of the highly interactive liquids dioxane and methylene chloride into cold-drawn PET was studied and shown to occur considerably more slowly than does the diffusion of these liquids into unoriented films.

SynopsisBy small-angle x-ray scattering, a systematic investigation was performed of the long spacing of poly(ethy1ene terephthalate) (PET) crystallized in a liquid environment. The results indicated that the measured long spacings were temperature dependent and apparently relatively insensitive to liquid type under the conditions studied. The kinetic nucleation model of polymer crystallization was found to adequately explain this dependence. The differences in the long spa&ngs between thermal and liquid-induced crystallization were in part rationalized in terms of the suspected supercoolings involved in the respective processes. Calculation of the spherulite growth rates for liquid-induced crystallization was made on the basis of the kinetic nucleation model and the classic theory of polymer-diluent crystallization. The results were shown to agree with inferential experimental observations of these growth rates and to elucidate the physics underlying liquid-induced crystallization. Finally, use of this growth rate theory in conjunction with a previous model for overall crystallization kinetics was shown to adequately describe and predict the diffusion-limited kinetics observed experimentally for most liquid-induced crystallization situations.1 -X ( t ) = exp(-Ktn)