Morphology dependent double yielding in injection molded polycarbonate/polyethylene blend

Abstract

Polycarbonate (PC)/polyethylene (PE) blend was injection molded at different molding temperatures. The morphological observation by scanning electronic microscope (SEM) indicated that the sample molded at 190 °C contained only uniformly dispersed spherical PC particles. The samples molded at 230 and 275 °C had a typical skincore structure, and there were many injection-induced PC fibers in the subskin. While the sample molded at 190 °C had the usual stress-strain behavior, the samples obtained at 230 and 275 °C showed apparently double yielding behavior. It was suggested that the double yielding points were morphology-dependent. The first one was the result of the yielding of PE at low strain, and the second one was caused by the yielding of the PC fibers. Moreover, it is the frictional force in the interfaces between the PC and PE that transferred the stress to the PC fibers, hence giving rise to the reinforcement of PE by PC.