Electrical behavior of high impact polystyrene/liquid crystalline polymer blends containing low content of carbon black

Abstract

This article presents a study of the structure and electrical behavior of carbon black (CB) containing immiscible polymer blends. A series of electrically conductive blends of high impact polystyrene (HIPS), liquid crystalline polymer (LCP), and CB was compounded and followed by a capillary rheometer extrusion process or by injection molding. In these immiscible blends, HIPS serves as a low surface tension matrix and LCP as a polar dispersed phase. Shear and elongational flow result in blend morphology consisting of highly elongated and oriented LCP particles dispersed in the HIPS matrix. The enhancement of conductivity in these blends is due to the affinity of CB to LCP and the formation of cocontinuous phase morphology, giving rise to conductive networks. Blends of various compositions were prepared using various processing conditions, emphasizing the relationship between morphology, rheology, and electrical properties. The presence of at least 20 wt % LCP and 2 phr CB under certain processing conditions (mixing sequence and temperature) is necessary to obtain stable resistivity, independent of the studied extrusion shear rate, and low resistivity values. In addition, the processing mode significantly affects the blends' structure and the resultant electrical properties. Hence, injection molding due to high shear rates, elongational flow, and fast cooling results in high structural and electrical anisotropy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1688–1696, 2006