The Effect of the Carbon Black Properties on the Elastomer Reinforcement
All the key particle properties, primary particle size (BET SSA), structure, and surface activity, are important for elastomer reinforcement plus the degree of dispersion achieved and the carbon black loading used in the elastomer composite.
Carbon Black Loading
There is an optimum loading observed for reinforcement properties such as tensile strength and tear and abrasion resistance, whereas stiffness increases steadily and elongation decreases with increasing loading. The optimum loading varies for different carbon black grades and elastomers. Up to the maximum for each grade, the increase of the number of carbon black aggregates contributes to an increase in the length of the rupture path which enhances the strength. The optimum occurs because the increasing interface created between the carbon black and rubber while increasing the carbon black amount is counteracted and finally dominated by restrictions concerning the ability to wet effectively the carbon black aggregates with polymer. Therefore, further increases of the carbon black loading beyond the optimum simply create flaws initiating the onset of the tensile failure.