ABSTRACT
434Recently, the industries related to rubber production and processing have been showing concern about environment protection and making efforts to reduce the amount of zinc oxide in rubber compounds. That has evoked our interest in the full or partial replacement of ZnO with other zinc salts that act as multifunctional ingredients. Zinc resinate is a salt that could be used in a natural rubber based compounds as a multifunctional additive of low zinc content with activating (in respect to the vulcanization process), plasticizing, dispersing, and antireversion effects.
The influence of zinc resinate on the main characteristics (vulcanization, mechanical, physicochemical, and dynamic) of compounds and vulca- nizates based on unfilled and reinforced natural rubber in the presence of accelerators differing in their chemical nature (mercaptobenzothiazole, tetrametiltiuram disulfide, N-cyclohexyl-2-benzothiazolyl sulfenamide, and N-tert-butyl-2-benzothiazyl sulfenamide) has been investigated.
In vulcanizates based on unfilled rubber, substitution of zinc oxide by zinc resinate at equivalent amounts lowers the minimum and maximum torque, leading to an increase in the scorch time and the optimal curing time. When the vulcanizates of rubber compounds are filled with carbon black, the effects of lacking zinc oxide are less pronounced and the parameters are much closer to those of the control sample with zinc oxide. When the silica- filled compounds contain bifunctional organosilane—a combination of zinc oxide and zinc resinate—the antireversion effect is more pronounced. Vulca- nizates containing zinc resinate or a combination of zinc oxide and zinc resinate have better dynamic properties than the respective control ones.
The results of our studies have demonstrated that when using zinc resinate as a polyfunctional additive, the content of zinc oxide in rubber compounds can be reduced, in some cases even eliminated, and certain properties of the vulcanizates improved.
