Effect of carbon black modification on the electrical reproducibility behavior of CB/HDPE composites

The carbon black (CB) or oxidative carbon black (CB-O) filled high-density polyethylene composites were prepared by melting blending. The influence of CB oxidation on the positive temperature coefficient (PTC) behavior，negative temperature coefficient (NTC) behavior and the electrical reproducibility of CB/HDPE and CB-O/HDPE composites were studied. It is shown that the NTC effect is decreased or even eliminated，the electrical reproducibility is improved and the PTC intensity is enhanced by CB oxidation. It is also revealed that the room temperature resistivity of CB-O/HDPE is increased by only 0.3 order compared with CB/HDPE，but is lower by one order than that of crosslinked CB/HDPE. The results are due to the increase of the polarity on the surface of CB-O，which is induced by the increase of the carboxyl and hydroxyl. Thus the agglomeration of CB-O at high temperature is restricted and the NTC effect of the composites is decreased. On the other hand，the reduction of the poor electrical conductive regions at boundaries of the crystallites on the surface of CB improves the electrical conductivity of the composites and the strong physical adsorption interaction between CB-O particles and HDPE improves the electrical reproducibility of the composites.