The Influence of the Method Used to Prepare Electrically Conductive Composites Based on Polyethylene, Polypropylene, and Carbon Black on their Properties at Elevated Temperatures

Abstract

An investigation was made of the process of preparing electrically conductive polyolefin composites based on blends of polyethylene and polypropylene with carbon black, with different orders of combination of the components. The effects of positive and negative temperature coefficients of electrical resistance were investigated. These were compared with the results of dilatometry, differential scanning calorimetry, dynamic mechanical analysis, and electron microscopy. The introduction of polypropylene into the polyethylene composite makes it possible to increase its heat stability and to eliminate the undesirable effect of a negative temperature coefficient. It was established that in polymer composites based on blends of polyethylene and polypropylene the effect of an increased positive temperature coefficient in the temperature region of melting of polyethylene appears even when carbon black is introduced only into the polypropylene. This is due to the sharp increase in volume of microregions during the melting of polyethylene in the blended composite.