Crystallization Behaviour of Polyamide 4 and Its Effect on Melting Point

Polyamide 4 (PA4) has received widespread attention as a bio-based polyamide exhibiting biodegradability. However, the melting and degradation processes of PA4 occur simultaneously, making it difficult to perform thermal processing. To expand the difference between the melting point temperature (T-m) and the thermal decomposition temperature (T-td), the crystallization and melting processes of PA4 were investigated to design strategies for regulating the crystallization. The isothermal crystallization and cold crystallization properties of PA4 were investigated with flash DSC. A special self-nucleation phenomenon which slowed the rate of recrystallization has been discovered. It confirms the significant differences in the morphology of crystals generated at differences temperatures. By controlling the crystallization process, the end-of-melt temperature (T-95) was greatly reduced. Nucleation and crystal growth at different temperatures provided a low melting temperature (T-95 = 246 degrees C), which was 20 degrees C lower than that for isothermal crystallization.