A Study of Vulcanization Accelerators. I. Compounds Which React Analogously to Rubber

Abstract

1. To elucidate the chemical behavior of rubber toward sulfur, a series of experiments was carried out using model compounds : tetralin, toluene, xylene, aniline, phenol, chlorobenzene, dichlorobenzene and naphthalene. Similar reactivities between rubber and the model compounds were observed. 2. The effects of the accelerators in the reactions of the model compounds with sulfur were different according to whether or not zinc oxide was present in the reaction system. 3. A detailed examination of the quantities of zinc sulfide formed in the reaction of tetralin with sulfur in the presence of zinc oxide showed that several vulcanization accelerators have similar activating effects in rubber vulcanization. 4. With tetralin as reactant, the quantity of zinc sulfide decreased suddenly at the reaction temperature 150° C, which was ascribed to the rapid decomposition of tetralin peroxide at this temperature. 5. The accelerating action of CPB, contrary to that of the other accelerators, was promoted by tetralin peroxide. 6. Tetralin peroxide had only a small inhibiting influence upon reactions with the amine accelerators, which is ascribed to the antioxidative nature of the amine derivatives; the inhibiting influence becomes larger in reactions with thiol derivatives or without any added accelerators. 7. Substituent effect on the hydrogen abstraction of the model compounds was primarily determined by the negativity of the relevant carbon atom. The order of the reactivity was found to be in accord with that toward the general “cationoid reagents”. 8. Analytical methods during and after the reactions were simplified for industry use.