Structural and Morphological Evolution upon Heating of Quenched Polyamide 1012
Yihan Yang, Mu Dong, Lihui Yuan, Xuan Li, Yong Zhou, Ping Zhu, Ying Zhao, Dali Gao, Shijun Zhang, Dario Cavallo, Alejandro J. Müller, Xia Dong, Dujin Wang
Abstract
In this study, the crystal form transition and semicrystalline morphology evolution of quenched polyamide 1012 (PA1012) during heating were investigated. Quenched PA1012 displayed a pseudohexagonal γ′ form at room temperature, in which the methylene segments adopted a trans conformation, the methylene group directly attached to the amide group was twisted, and the hydrogen bonding pointed in all directions. During heating, the γ′ form gradually transformed into the γ form as the trans methylene sequences that are away from the amide group further twisted, and the dihedral angle between the amide and methylene plane exhibited a narrow distribution. The transition onset temperature was near the glass transition temperature of quenched PA1012. The semicrystalline morphology of quenched PA1012 was characterized as a loose network consisting of a disordered arrangement of thin lamellae with poorly defined boundaries. As the annealing temperature increased, the lamellae became more perfect and thicker, while the morphological type remained the same.