CRYSTALLIZATION OF POLYETHYLENE AT HIGH PRESSURE: A KINETIC VIEW.

A model for the crystallization kinetics of polymers is outlined and is used to interpret observations of the crystallization of PE at high pressures. This model introduces a distinction between sigma //e the lamellar surface energy which controls the lamellar thickness, and sigma //e', the surface nucleus surface energy which controls the growth rate. Differential scanning calorimetry and electron microscopy data for several polyethylenes crystallized at pressures of up to 8 kb are preseinted. It is found that sigma //e increases markedly with pressure leading to the formation of very thick crystals at high pressures. Fractionation effects and the differences in behavior between different polyethylenes are also discussed.