The positive temperature coefficient (PTC) behavior of polymers having a high melting temperature, such as nylon, polyvinylidene fluoride, polyester, and polyacetal, was investigated. Carbon black and nickel powder were used to investigate the influence of their conductive fillers on PTC intensity. The polymer/filler composite was irradiated with gamma rays at dosages of 50, 100, and 150 kGy for the purpose of reducing the negative temperature coefficient (NTC) of a conductive composite. It was found that the PTC temperature depended on the melting point of the polymer matrix. The crosslinking structure enhanced the electrical stability and decreased the NTC effect of the composites. (C) 2004 Wiley Periodicals, Inc. J. Appl Polym Sci 92: 394-401, 2004.