Thermally induced double‐positive temperature coefficients of electrical resistivity in combined conductive filler–doped polymer composites

Polymer composites of low‐density polyethylene/polypropylene/graphite/vanadium dioxide (LDPE_0.8/PP_0.2/Gr_0.4/VO₂) are prepared by classical melt‐mixing technology and show a notable double positive temperature coefficient of electric resistivity (PTC), which originates from the combined effect of highly conductive Gr and VO₂ with a thermal phase transition. When the weight ratio of VO₂ is 8 wt %, the positive temperature coefficient intensity (PTCI) for the composites reaches 3.85 orders of magnitude. The model system demonstrates the reason for the improvement in the PTC performance of the polymer composites by analyzing the construction of the conductive networks. Therefore, the addition of phase‐transition compounds may be a promising path to improving PTC materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44876.