Conductive composites of high surface area carbon black/polypropylene

Conductive properties and volume resistivity-temperature characteristics of high surface area carbon black (Ketjen black, KB) filled polypropylene (PP) composites were studied. The results show that as the KB contents reach to 0.5%~1.5% (volume fraction), KB/PP composites appear electrical percolation behavior which exhibits the excellent room temperature conductivity. Meanwhile, the volume resistivity of composites-temperature characteristic curve shows a special negative temperature coefficient-positive temperature coefficient-negative temperature coefficient (NTC-PTC-NTC) characteristic of three stages. The volume resistivity of the KB/PP composites system increases with the temperature, appearing first NTC effect as a decline in the first, and then PTC effect and the second NTC effect. The first NTC of KB/PP composites system has a good effect of the stability and repeatability within a relatively low temperature range. The superposition of the conductive effect of the electronic transition from KB surface and matrix volume expansion effect cause the system to appear three stages feature.