טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShemesh Rotem
SubjectElectrical Behavior of HIPS/LCP/CB Immiscible Blends
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Arnon Siegmann (Deceased)


Abstract

This paper presents a study of the structure and electrical behavior of CB containing immiscible polymer blends. A series of electrically conductive blends of high impact polystyrene (HIPS), liquid crystalline polymer (LCP) and carbon black (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 co-continuous 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 20wt% LCP and 2phr CB under certain processing conditions (mixing sequence and temperature) are 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.