Formula for calculating hardness and carbon black

Hardness is the index of the degree of softness and hardness of direct reaction rubber. It refers to the ability of rubber material to resist hard material pressing into the surface locally. Different kinds of rubber have different hardness. When using recycled rubber to produce rubber products, many rubber products with special requirements for hardness need to adjust the hardness of recycled rubber vulcanizate through rational formulation design. Carbon black is the most commonly used method to adjust the hardness of recycled rubber. Reinforcement filler. What is the relationship between the hardness of recycled rubber and carbon black? Why can the hardness of recycled rubber vulcanizate be adjusted by carbon black?