Influence of Thermal History on Primary Nucleation and Crystal Growth Rates of Isotactic Polystyrene

摘要

Polymer crystallization processes from the melt are made up with two main mechanisms such as a primary nucleation and a crystal growth. The crystal growth rate is affected mainly by crystallization temperature but the nucleation rate is influenced by many experimental conditions such as thermal history prior to the crystallization. For example, nucleation density is influenced by the melt temperature at which the previously crystallized sample is melted and then cooled down to a given crystallization temperature. The effect of melting condition on nucleation is often called as a memory effect in the melt. Boon et al have studied extensively the influence of the thermal history on nucleation for i-PS by dilatometry. However, the numbers of nuclei are not observed directly but they are estimated from the dilatometry data. In the present work, the number of nuclei and the nucleation rate are directly measured by counting the number of spherulites as a function of time and temperature.