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 crosslinking modification could increase the room temperature resistivity of the composites. Moreover, as the crosslinking 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 omega 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-crosslinked composites, and the cyclic stability was optimal. In the PTC strength test, the result yielded 3.4 in three tests.