Preparation and PTC properties of multilayer graphene/CB/HDPE conductive composites with different cross-linking systems

Multi-layer graphene/carbon black (CB)/high density polyethylene (HDPE) conductive composites with different systems were prepared by melt compounding. The composites were subsequently cross-linked and modified using peroxide cross-linking and radiation cross-linking techniques. The effects of these different cross-linking systems on the room temperature resistivity, positive temperature coefficient (PTC) strength, cyclic stability, and crystallinity of the multi-layer graphene composites were investigated. The results demonstrated that cross-linking modification could increase the room temperature resistivity of the composites. Moreover, as the cross-linking degree increased, the PTC strength also increased, and the negative temperature coefficient (NTC) effect disappeared. Within the range of room temperature resistivity less than 1 Ω cm, the maximum recommended usage of peroxide was 0.3 %. Among the composites with the same ratio, the dual cross-linking system exhibited the best electrical properties. The PTC strength increased by one order of magnitude compared to the un-cross-linked composites, and the cyclic stability was optimal. In the PTC strength test, the result yielded 3.4 in three tests.