Low heat generation from organic zinc as a curing activator in rubber and rubber composites under large strain

Abstract

ZnO is a conventional activator in sulfur curing systems, but its excessive release can cause adverse effects to the human body and the environment. Using organic zinc instead of zinc oxide not only decreases the amount of zinc but also disperses the zinc into the natural rubber (NR) matrix more effectively. The results showed that the six organic zinc compounds accelerated the curing process and weakened the Payne effect compared to those with ZnO. Dynamic frequency scan tests of the vulcanizates in linear (small strain) and nonlinear (large strain) viscoelastic regions were performed. Different from that at small strain, there was a great change in the storage modulus, loss modulus and loss factor at large strain. For unfilled NR, the systems with zinc oleate, zinc 2-ethylhexanoate and zinc acetate as activators showed a weaker Payne effect and low heat generation because of the homogeneous dispersion. For NR/CB (carbon black) composites, the systems with zinc acetate, zinc o-glycerol and zinc 2-ethylhexanoate showed a weaker Payne effect and low heat generation at large strain and high frequency due to the homogeneous dispersion and the strong interaction with CB particles. These results will help to clarify the advantages of organic zinc instead of zinc oxide in reducing heat generation for rubber products.

Influence of active, nano, and functionalized zinc oxide particles on the mechanical, cytotoxicity, and thermal stability of carbon black filled SBR/NR blends

“…A higher G ′ shows a high filler–filler interaction 61 . Wang et al 62 have explained the Payne effect of unfilled NR and NR/CB vulcanizates with different types of organic zinc. The study demonstrates that uniform dispersion of ZnO in the rubber matrix improves processing fluidity as well as filler dispersion and significantly reduces the Payne effect in the matrix.…”