Hydrotalcite/unsaturated Carboxylic Acid Systems as Coagents in Ethylene-Propylene Copolymer Vulcanization

The aim of this work was to study the activity of several hydrotalcite/unsaturated acid systems in the peroxide crosslinking of ethylene-propylene copolymer (EPM). Allylmalonic, citronellic, crotonic, itaconic, sorbic and undecylenic acids, as well as monoallyl maleate, were applied to ensure the activity of hydrotalcite in the peroxide vulcanization of EPM. In this article, we discuss the effect of the obtained coagents with respect to their particle size and tendency to agglomerate, as well as the effect of the applied type of unsaturated acid on the vulcanization kinetics of rubber compounds. The influence of hydrotalcite/unsaturated acid systems on the crosslink density, the mechanical properties of the vulcanizates and their stress relaxation tendency under external deformation were also studied. Hydrotalcite/unsaturated acid systems seem to be active as coagents in the crosslinking of EPM with peroxide. The type of unsaturated acid considerably influences the activity of hydrotalcite toward the ethylene-propylene copolymer. The application of such coagents increases the crosslink density of the vulcanizates and improves their mechanical properties.