Abstract: Carbon fiber oxidized by KMnO₄ was combined with ethylene vinyl acetate(EVA) copolymer, the obtained composite shows a fine stability of thermal cycles and nearly unchanged switching temperature under thermal cycles, at the same time negative temperature coefficient(NTC) phenomenon is eliminated. Solvent-extraction method is used to examine the interaction between EVA and CF and insolublity with the gel structure were found. The crosslinking network in the gel adsorb CF intensely which makes CF disperse in EVA uniformly, orientate consistently, combine with EVA tightly and shows the elimination of NTC phenomenon. The switching temperature of the composite in the heating process is not identical with that of the composite in the cooling process absolutely, but the temperatures in the above two processes are consistent with the outset of melting temperature and the end of crystallization temperature respectively.

Key words: Positive temperature coefficient(PTC), Negative temperature coefficient(NTC), Carbon fiber(CF), Ethylene-vinyl acetate(EVA) copolymer, Gel