Positive temperature coefficient effect and mechanism of compatible LLDPE/HDPE composites doping conductive graphite powders

摘要

Linear low density polyethylene (LLDPE)/high density polyethylene (HDPE) blends doped conductive graphite powders were constructed by the traditional melt-blending method to acquire the conductive compatible polymer composites, and corresponding positive temperature coefficient (PTC) effect of electrical resistivity was investigated. The results indicated that the room-temperature resistivity gradually decreased and PTC effects were remarkably enhanced by regulating the graphite contents or LLDPE/HDPE ratios. Especially, with increasing graphite contents, the polymer-fixed composites showed the notable double PTC effects, originating from the volume expansion of the co-crystallization or their fraction. Whereas, with increasing the LLDPE/HDPE ratio, the PTC effects of the graphite-fixed composites occurred at the lower temperature, even far below the melting points of the co-crystallization. Therefore, the regulation of co-crystallization morphology of compatible polymer matrices was a new idea in the improvement of PTC materials. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46453.