Resistivity‐temperature behavior of carbon fiber filled semicrystalline composites

Carbon fiber (CF) filled low‐density polyethylene (LDPE) composites were prepared by the conventional melt‐mixing method. The distribution of CF in the composite was studied by wide‐angle X‐ray diffraction (WAXD) and scanning electron microscope (SEM) observations. A phenomenological model was proposed to illustrate the resistivity‐temperature behavior of CF‐filled semicrystalline composites. The effects of the content and aspect ratio of CF on the positive temperature coefficient (PTC) and the room temperature resistivity were elucidated. A balance between the PTC intensity and the room‐temperature resistivity can be achieved by using a mixture of CFs with low and high aspect ratios. The negative temperature coefficient (NTC) phenomenon can be effectively eliminated by crosslinking under γ‐ray radiation, and the crosslinked composite exhibits a higher PTC intensity and PTC transition temperature than the noncrosslinked counterpart.