Metallic methacrylate as a reactive filler to reinforce ethylene-propylene-diene rubber

The reinforcement of non-polar ethylene-propylene-diene rubber (EPDM) by th e polar metal salts of methacrylic acid was achieved by directly mixing the salt into EPDM at a high level and curing with peroxide. Mechanical proper ties and crosslink density of the vulcanizates were investigated. Wide-angl e X-ray diffraction (WAXD) and Fourier transform-infrared spectroscopy (FTI R) were employed to analyze the reactivity of zinc dimethacrylate (ZDMA) in EPDM compounds before and after vulcanization. It was observed that the co mmercial ZDMA or magnesium dimethacrylate (MDMA) can greatly improve the ha rdness end tensile strength of the EPDM vulcanizates, while retaining a hig h elongation at break. WAXD and FTIR revealed that ZDMA is a reactive fille r in the EPDM matrix during peroxide curing. The crosslink density of the v ulcanizates was determined by equilibrium swelling. Covalent crosslinks and ionic crosslinks were distinguished by an acidolysis treatment. Ionic cros slinks were greatly improved by increasing the amount of zinc dimethacrylat e or dicumyl peroxide, and the relationship between mechanical properties a nd crosslink density indicates that the tensile strength of the vulcanizate was principally dependent on ionic crosslink density.