To some extent, zinc stearate can partially replace stearic acid and zinc oxide, but stearic acid and zinc oxide in rubber cannot fully react and both have their own roles.
Zinc oxide and stearic acid form an activation system in the sulfuration system, whose main functions are as follows:
1. Activated vulcanization system:
ZnO and SA can produce zinc soap, improve the solubility of ZnO in rubber, and form complex with good solubility in rubber with accelerator, activate accelerator and sulfur, and improve vulcanization efficiency.
2. Increase the crosslinking density of vulcanizates:
ZnO and SA produce soluble zinc salts, which chelate with crosslinked bonds to protect weak bonds, enable sulfide to generate short crosslinked bonds, add new crosslinked bonds, and improve crosslinked density.
3, improve the aging resistance of vulcanized rubber:
In the process of using vulcanizates, the polysulfide bond breaks and the hydrogen sulfide generated will accelerate the aging of rubber. However, ZnO interacts with hydrogen sulfide to generate zinc sulfide, which consumes hydrogen sulfide and reduces the catalytic decomposition of hydrogen sulfide on the crosslinked network.In addition, ZnO can suture the broken sulfur bond and stabilize the crosslinked bond.
4. Different reflection mechanisms:
In different vulcanization coordination systems, the action mechanism of different vulcanization promoters is very different, and the action mechanism of ZnO reacting with SA to form zinc stearate intermediate is also different from that of using zinc stearate alone.
Therefore, the formula design needs to choose the appropriate coordination according to different design ideas.