Fracture and Deformation of Extended-Chain Crystals in Poly(ethylene Terephthalate)/Bisphenol-A Polycarbonate Blends Crystallized at High Pressure

Abstract

With a combination of three-dimensional crystal ordering and long-chain molecular orientational ordering, the extended-chain crystals of polymers are ideal system for the studies on low-dimensional physics, and have potential applications as functional components. In this study, poly (ethylene terephthalate) / bisphenol-A polycarbonate (PET/BAPC) blend samples were prepared with solid phase forming technique under high pressure, and extended-chain single crystals with large c-axis thickness were formed within a relative short time. The fracture and deformation behaviors of the grownup crystals were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Morphological observation showed that most of the extended-chain crystals were endowed with perfect appearance after the sample fracture. However, there were still a few crystals fractured apart, along or perpendicularly to their c-axis direction, or with cohesive fracture surfaces. Fractured spherulites with extended-chain lamellae as substructures were also disclosed in extended-chain crystals with AFM. Furthermore, the parallel lamellae deformed and changed their striation direction during the crystal growth, as was observed on a kind of extended-chain crystals grown in a PET oligomer and BAPC blend (PETO/BAPC). This study may be instructive to the improvement of the separation technique of such single crystals, so as to hasten their real applications.