The role of stearic acid and zinc oxide in rubber compounding

To some extent zinc stearate can partially replace stearic acid and zinc oxide, but stearic acid and zinc oxide in rubber can not be fully reactive and have their own role.

Zinc oxide and stearic acid in the sulfur vulcanisation system constitute the activation system, its main functions are as follows.
1, activation of the vulcanisation system: ZnO and SA generate zinc soap, which improves the solubility of ZnO in rubber, and with the accelerator to form a complex with good solubility in rubber, which activates the accelerator and sulphur.
Activate the accelerator and sulfur, improve the vulcanisation efficiency.

2、Improve the cross-linking density of vulcanised rubber: ZnO and SA generate soluble zinc salt, zinc salt and cross-linking bond chelate, protect the weak bond, so that the vulcanisation generates short cross-linking bond, and increase the new
Crosslinking bond, improve the crosslinking density.

3, improve the aging resistance of vulcanized rubber: vulcanized rubber in the process of use, polysulfide bond breakage, the generation of hydrogen sulfide will accelerate the aging of rubber, but ZnO and hydrogen sulfide to generate zinc sulfide, consumption of hydrogen sulfide, reducing the hydrogen sulfide on the catalytic decomposition of the crosslinked network; in addition, ZnO can sew broken sulfur bond, the crosslinked bonds play a stabilizing role.

4, reflecting different mechanisms: in different vulcanisation with the system, different vulcanisation accelerator mechanism is very different, ZnO and SA reaction to form zinc stearate intermediates and the role of separate use of zinc stearate mechanism is not the same.

Therefore, it is necessary to choose the appropriate coordination system according to different design ideas in the formulation design.