Kinetic analysis of PA4 thermal degradation: Thermal stability with respect to crystallinity

Polyamide 4 (PA4) has garnered considerable attention due to its fully bio-based origin and biodegradability as a high-performance polyamide. Nevertheless, thermal degradation during the melting process impedes thermal processing, thereby constraining its potential for engineering plastics applications. To clarify the thermal degradation reactions of PA4 amidst intricate physical and chemical transformations, establishing a theoretical foundation for the thermal stability modification, we conducted a comprehensive analysis of PA4 thermal degradation coupled with crystallization, considering kinetics and reaction mechanisms. Calculation of reaction activation energies and mechanism functions revealed that PA4 pyrolysis is a two-stage compound process, with distinct degradation mechanisms attributed to the crystalline and amorphous regions. Additionally, the thermal degradation mechanism of the PA4-CaCl2 composite system at varying crystallinity levels was illustrated. The incorporation of Ca strengthens intermolecular forces in the samples, leading to an increased overall stability. Simultaneously, a notable alteration in the reaction mechanism was observed in the crystalline zone lacking the Ca phase.