▎ 摘　　要

In this work, the positive-temperature-coefficient (PTC) effect of resistivity of low density polyethylene/graphite powder (45%) composites (LDPE/GP) in the presence of graphene before and after crosslinked was comparatively investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy, Raman spectrum, and resistivity-temperature test. The composites showed the repeatability of the PTC effect with heating cycles and a certain improvement in the room temperature resistivity. After crosslinked, the composites presented a higher PTC trip temperature at about 140 degrees C than pure LDPE (T-m = 112 degrees C), and stronger PTC intensity than room temperature resistivity (over 5 orders of magnitude). The results from DSC, XRD, and Raman spectrum indicated that the addition of graphene resulted in the gradual enhancement in the crystallization of LDPE matrix, which was the origin of the improvement of the PTC behavior of the composites. As a result, we could conclude that the additional conducting filler could improve the PTC effect of the conducting composite system. (C) 2013 Society of Plastics Engineers