MECHANICAL AND ELECTRIC PROPERTIES OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE AND CARBON-BLACK PARTICLE BLENDS

Composite materials of ultra-high-molecular weight polyethylene (UHMWP E)-carbon black (CB) particles were prepared by gelation/crystallizati on from solution in order to obtain the composite materials with vario us electric conductivities. UHMWPE-CB compositions chosen were 1/0.25, 1/0.5, 1/0.75, 1/1, 1/3, 1/5, and 1/9. Electric conductivity increase d with increasing CB content and was in the range of 10(-9) to 1 Omega (-1) cm(-1) corresponding to semiconductors. These values were almost independent of temperature up to 175 degrees C indicating thermal stab ility. Elongation was carried out in a hot oven at 135 degrees C. Draw ability was less pronounced as CB content increased. For example, the maximum achievable draw ratio of 1/1 composition (50% CB content) was 70-fold, while that of 1/0.25 (20% CB content), 150-fold. The correspo nding Young's modulus and tensile strength for the 1/0.25 blend were 7 3.6 and 1.31 GPa, respectively, while those for the 1/1 blend were 25. 4 and 0.46 GPa, respectively. The materials with CB > 83% could not be elongated in spite of good impact resistance. The electric conductivi ty for the drawn blends was anisotropic. The values in the stretching direction decreased with increasing draw ratio, while the values in th e thickness direction increased slightly.