Crystallization and melting behavior of isotactic polybutene-1 at high pressures

Abstract

An equation has been developed for the study of the kinetics of polymer crystallization at high pressures using differential scanning calorimetry (DSC) in the dynamic mode of operation. The activation energy for the crystallization of isotactic polybutene-1 (PB-1) has been determined to be ca. 20 kcals/mol; this has been attributed to the transport of chain segments to the site of crystallization. The melting behavior of form-I PB-1 crystals has been studied by using a high-pressure differential thermal analyzer (DTA) setup and high-pressure DSC. The melting temperature T_m does not show any significant change with pressure in the low-pressure region up to 1.2 kbar; beyond this point a large increase in T_m with pressure was observed. This unusual low-pressure behavior of PB-1 has been attributed to formation of intermediate form I', which has a lower melting point than form I.