Effect of Hydrostatic Pressures on the Crystallization Kinetics of Natural Rubber

The crystallization kinetics of natural rubber were investigated, utilizing dilatometric techniques, over an extended temperature range under hydrostatic pressures up to 800 kg/cm2. Irrespective of pressure, the isothermal crystallization displayed good adherence to the general mathematical formulation of the kinetics of phase changes as modified for the crystallization of chain‐like molecules. Nucleation control is indicated at the higher temperatures. The rate of crystallization increases with increasing pressure at constant temperature as a consequence of the increased supercooling. At lower temperatures, transport terms dominate with the rate increasing with temperature at constant pressure. Over the temperature range accessible to study, the data are quantitatively explained by utilizing an activation energy for transport which is independent of temperature but which increases slightly with pressure.