The effect of surface free energy on the positivw temperature coefficient (PTC) of carbon black/thremoplastic resin composites was investigated.The thermoplastic resins such as EVA, LDPE, LLDPE and HDPE were used with the addition of 30 wt.% of the carbon black. the surface free energy of the composites was studid in the context of the to liquid contact angle measurements ,i.e., deionizd water and diiodomethane. It was observed that the resistivity on PTC composites was greatly increased near the crystalline melting temperatyre, due to the thermal expansion of polymericmatrix.