To some extent, zinc stearate can partially replace stearic acid and zinc oxide, but in rubber, stearic acid and zinc oxide cannot react completely and both have their own roles.Zinc oxide and stearic acid form the activation system in the sulfur sulfide system, and its main functions are as follows:
1. Activated vulcanization system:ZnO and SA act to produce zinc soap, improve the solubility of ZnO in rubber, and form complex with good solubility in rubber by acting with accelerator, activate accelerator and sulfur, and improve the vulcanization efficiency.
2. Improve the crosslinking density of vulcanized rubber:ZnO and SA generate soluble zinc salts, which chelate with crosslinked bonds to protect the weak bonds and cure short crosslinked bonds, and add new crosslinked bonds to improve the crosslinked density.
3, improve the aging resistance of vulcanized rubber:During the use of vulcanized rubber, the polysulfide bond breaks, and the hydrogen sulfide generated will accelerate the aging of rubber. However, ZnO reacts with hydrogen sulfide to produce zinc sulfide, consumes hydrogen sulfide, and reduces the catalytic decomposition of hydrogen sulfide on the cross-linked network.In addition, ZnO can suture the broken sulfur bond and stabilize the cross-linked bond.
4. Different mechanisms:In different vulcanization coordination systems, the mechanism of action of different vulcanization promoters is very different, and the effect of ZnO and SA reaction to form zinc stearate intermediate is different from that of zinc stearate alone.
Therefore, the formulation design needs to choose the appropriate coordination according to different design ideas.
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