Localization of carbon black particles in polypropylene/polyethylene polymer blend and its electrical resistivity

The effects of the localization of carbon black (CB) particles on the electrical resistivity of a CB-filled polypropylene (PP)/polyethylene (HDPE) polymer blend were investigated. CB particles were first compounded with PP. The CB/PP composite was subsequently compounded with HDPE to make the 2-step blending composite. CB particles dispersed in PP phase tend to move from PP phase to HDPE phase in the 2-step blending composite. Consequently, CB particles are localized at the PP/HDPE interface. When both of the PP and HDPE phases are continuous, it is expected that CB particles localized at the PP/HDPE interface will form a conductive network in the blend. Experiments showed that the 2-step blending composite exhibited a lower room temperature resistivity and much higher PTC (positive temperature coefficient) intensity than the simultaneous blending composite. These results suggest that CB particles localized at the PP/ HDPE interface are effective for the electrical conductivity, and that the conductive network formed at the interface is prone to expand with the thermal expansion of the matrix polymer. The localization of CB particles was confirmed by transmission electron microscopy (TEM) observations.