The role of stearic acid in rubber processing
During rubber processing, stearic acid is added as an auxiliary material, and the proportion of addition is very small. Usually 0.5-3 parts of stearic acid are added for every 100 parts of rubber, but it is indispensable.
As vegetable oil-based fatty acids, when added in a certain proportion during the processing of rubber (tire), they have the following four functions:
1. Softening and plasticizing effects.
2. As an external lubricant.
3. It is beneficial to the full diffusion of carbon black, white carbon black and zinc oxide.
4. Reaction with zinc oxide or alkaline accelerator can promote its activity. It is also the main vulcanization accelerator and can play the role of a second accelerator. Can accelerate hardening.

Stearic acid has a greater impact on the rubber. Its effect is opposite to that of carbon black. It will significantly reduce the viscosity of the rubber, improve process performance, and significantly increase the plasticity of the rubber.
The length of the fatty acid carbon chain has no effect on its efficacy. For example, lauric acid and oleic acid also have a good softening effect.
Excessive unsaturation of oleic acid will interfere with the rubber processing process, and oleic acid also tends to increase rubber aging.
Lauric acid has a high acid value, which will greatly delay the vulcanization of rubber.