Synthesis and thermal degradation mechanism of a semi-aromatic copolyamide from renewable sources

Bio-based polyamide has attracted increasing attention in recent years. However, it remains a challenge to synthesize bio-based polyamide combining excellent high temperature resistance and mechanical properties. And the thermal degradation mechanism of pentamethylenediamine-based semi-aromatic polyamide has not been reported. In this work, a semi-aromatic bio-based polyamide (PA5T/56) with high melting point, excellent mechanical properties, and high temperature resistance comparable to petroleum-based polyamide (PA6T/66) was successfully synthesized. The thermal degradation behaviors of PA5T/56 and PA6T/66 were characterized via TG-FTIR-MS and Py/ GC–MS, and the possible thermal degradation mechanisms were proposed. Different from PA6T/66, unique pyridines were traced in the degradation volatiles of PA5T/56 because of the cyclization tendency of the pentamethylenediamine structural unit. Moreover, the thermal degradation mechanism of PA5T/56 was mainly dominated by cleavage-cyclization of C–N bond accompanied by high-temperature radical cleavage reaction. This work will provide theoretical and practical basis for the design of bio-based high temperature resistant polyamide.