Synthesis and non-isothermal crystallization kinetics of polyamide 66 copolymers containing alicyclic structures

Abstract

To further improve the performance of PA66 and expand its applications, a new strategy was proposed to introduce an alicyclic structure into PA66 chain by the copolymerization method. Initially, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane (MACM) was reacted with 1,6-adipic acid to form MACM6 salt, and then, it was copolymerized with PA66 salt to synthesize PA66/MACM6 copolymers with alicyclic structures. PA66/MACM6 copolymers exhibited good thermal stabilities, and the presence of alicyclic structure had no significant effect on their thermal stabilities. Notably, the crystallization temperature, crystallinity and melting point of the PA66/MACM6 copolymer decreased gradually with increasing MACM6 content, indicating that the addition of the MACM6 segment disrupted the regularity of the original PA66 chain. Moreover, as the melting point of the PA66/MACM6 copolymer was in between 223.9 °C and 254.8 °C, it could be processed in a wide temperature range to meet the requirements of different industrial applications. The non-isothermal crystallization kinetics of PA66/MACM6 copolymers were investigated using the Jeziorny and Mo methods, and the crystallization activation energy was calculated using the Kissinger method. The results indicated that the introduction of the MACM6 segment into the PA66 chain by copolymerization inhibited its crystallization and increased its crystallization activation energy, thereby reducing its crystallization rate. In addition, PA66/MACM6 copolymers exhibited improved toughness with a slight decrease in the strength. When the content of MACM6 reached 40 wt%, the elongation at break of PA66/MACM6-40 was about 760% higher than that of PA66, suggesting its high toughness.