Effect of argon plasma treatment on the PTC and NTC behaviors of HDPE/carbon black/aluminum hydroxide nanocomposites for over-voltage resistance positive temperature coefficient (PTC)

In this investigation, carbon black and inorganic flame retardants were added into high density polyethylene (HDPE) to produce an over-voltage resistance positive temperature coefficient (PTC) composite film. The results of this study indicated that the plasma treatment enhanced the surface activity and the structural completeness of HDPE, which enhanced the PTC intensity of the composite. As HDPE was treated by plasma with 40 W for 3 min, the PHDPE possessed the maximum free radicals of 0.958 × 10− 6 mol g− 1, which coincided with the result of gel content (43.98%) of PHDPE. In addition, it was found that the effective cross-linking method of PHDPE with initiator (DCP) and 60Co γ-ray radiation was better than the traditional radiation cross-linking method in cross-linking the structure of the composite, the former reduced the radiation dosage (was smaller than 20 Mrad) greatly to increase the PTC intensity of the composite obviously, and to eliminate the NTC effect of the composites fully. The composite of P(403)C33.7A28D2-20 possessed good PTC intensity (6.07 orders of magnitude) in all composites, passed the over-voltage resistivity test successfully, and possessed good structural stability. In accordance with the results of the thermal expansion coefficient (α) of TMA measurement, it could be found that the CTE was possessed at the highest and a fundamental relationship exists between the PTC behavior and thermal expansion coefficient (α).