Effect of reinforcement filler on vulcanization, diffusion, mechanical, and electrical properties of natural rubber

The present work investigates the properties of natural rubber (NR) filled with different contents of reinforcing carbon black (CB) and other compounding ingredients. The curing characteristics were tested at 157°C. It was found that the equilibrium solvent uptake ( Q _max ) decreases with the increase of the CB concentration due to reduction of the free volume. Mechanical properties such as tensile strength and hardness of CB filled rubber composites were remarkably improved, indicating the inherent reinforcing potential of CB. The percentage of elongation at break of filled CB rubber was found to be lower than that of pure NR. The dielectric constants ( ε′), dielectric loss ( ε″), and alternating current (AC) electrical conductivity ( σ _AC ) were investigated for all samples as a function of frequency and temperature. It is concluded that the high CB content causes the formation of channels, increasing the AC conductivity of the composites.