MORPHOLOGY AND ELECTRIC-CONDUCTIVITY OF CROSS-LINKED POLYETHYLENE-CARBON BLACK BLENDS PREPARED BY GELATION CRYSTALLIZATION FROM SOLUTIONS/

Ultra-high-molecular-weight polyethylene (UHMWPE)-carbon black (CB) bl ends were prepared by gelation/crystallization from PE dilute solution s containing CB particles. The UHMWPE/CB composition chosen were 1/0.1 5, 1/0.25, 1/0.5, 1/0.75, 1/1, 1/3, 1/5, and 1/9, etc. The crosslinkin g of PE chains was performed by chemical reaction of dicumylperoxide a t 160 OC. X-ray diffraction patterns indicate that the crystallinity o f PE within the blends decreased drastically through the chemical reac tion at high temperature. The sample preparation method by gelation/cr ystallization provided the UHMWPE-CB system with various CB contents u p to 90% and the conductivities for the resultant specimens were in th e range from 10(-9) to 1 Omega(-1) cm(-1) corresponding to the electri c conductivity range of semiconductors. The blends assured thermal sta bility of electric conductivity by cross-linking of PE chains, althoug h the mechanical property such as the storage and loss moduli were ver y sensitive to temperature. The conductivity of the blends with CB con tent greater than or equal to 20% were almost independent of temperatu re up to 220 degrees C and the values in the heating and cooling proce sses were almost the same. On the other hand, for the UHMWPE-CB blends with 13% CB content corresponding to the critical one, temperature de pendence of electric resistivity showed positive temperature coefficie nt (PTC) effect. The PTC intensities for non-crosslinked and cross-lin ked materials were lower than that of the corresponding low-molecular- weight-polyethylene (LMWPE)-CB blend but the maximum peak appeared at 160 degrees C which is higher than the peak temperature of LMWPE-CB bl end.