Mechanical and electric properties of ultra-high molecular weight polyethylene and carbon black particle blends

Composite materials of ultra-high-molecular weight polyethylene (UHMWPE)-carbon black (CB) particles were prepared by gelation/crystallization from solution in order to obtain the composite materials with various 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 increased 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 stability. Elongation was carried out in a hot oven at 135 degrees C. Drawability 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 corresponding Young's modulus and tensile strength for the 1/0.25 blend were 73.6 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 conductivity for the drawn blends was anisotropic. The values in the stretching direction decreased with increasing draw ratio, while the values in the thickness direction increased slightly.