Electrical Resistivity of PP/PE Composite Filled with Amino-silane Treated Carbon Black and Its Thermal Behavior

Carbon black (CB)-filled composites of polyethylene (PE), polypropylene (PP), and PP/PE blend with weight composition of 40/60 have been prepared by twin screw extruder, and their electrical resistivities have been investigated. In order to improve the surface properties of CB, γ-aminopropyl trimethoxysilane (APS) was used for the surface treatment of CB. The surface treatment of CB by APS was found to effectively decrease percolation threshold, φc, i.e., the electrical resistivity showed drastic decrease when the CB content was larger than φ c. Temperature dependence of APS-treated CB/PP/PE composites exhibited almost constant electrical resistivity (~106 Ωcm) in the range of 25-130°C, and it was increased drastically to ~1012Ωcm above the melting temperature of PE, resulting high positive temperature coefficient (PTC) intensity (ca. 106). This high resistivity was maintained even at the higher temperature than 150°C, and only weak negative temperature coefficient (NTC) behavior was observed. The surface treatment of CB by APS is effective to obtain CB/PP/PE composites having excellent thermal electrical property as a switching material.