Positive temperature coefficient effect of LMWPE-UHMWPE blends filled with short carbon fibers

Composites of ultra-high molecular weight polyethylene (UHMWPE), low molecular weight polyethylene (LMWPE) and carbon fibers (CF) were prepared by gelation/crystallization from solution. The maximum intensity of PTC (positive temperature coefficient), the magnitude being ca. 9 orders, was found for a LMWPE/UHMWPE composition of 9/1 containing 23.5 vol% CF, i.e. a much higher amount of the filler than in the percolation threshold (12-15 vol%). The elimination of the NTC (negative temperature coefficient) effect and a good reproducibility were achieved by using UHMWPE as one of the composite components because of its very high viscosity. (C) 2004 Elsevier Ltd. All rights reserved.