Use of Multifunctional Crosslinking Agents in the Electron Beam Cure of Elastomers

Electron beam curing of elastomers involves applying an intense and precise stream of high energy electrons capable of radical induced crosslinking. In the presence of multifunctional crosslinking agents (coagents), induced radicals can undergo addition reactions via reactive sites on the coagent or via hydrogen abstraction and subsequent crosslinking. Radically induced curing of elastomers in the presence of coagents produces higher crosslink density and physical properties when compared to the elastomer alone.  These properties are directly related to the composition of the crosslinks formed.

In this study the influence of electron beam radiation dosage on crosslinking ethylene propylene diene monomer (EPDM) in the presence of various coagents was investigated. The influence of coagent level and coagent type on physical properties was investigated. It was shown that increasing coagent level at low irradiation dosage (50 kGy) minimally influences crosslink density and physical properties. The impact of methacrylate multifunctional coagents at various loadings was also investigated. Increase in physical properties as a function of increasing coagent level was observed.

The data was compared with a standard peroxide cured system also containing the same coagents. Peroxide vulcanization at 160°C was carried out on EPDM samples. Physical property and crosslink density of electron beam irradiated samples were compared with the peroxide cured samples. Further, peroxide cured samples were formulated to an equivalent crosslink density as that of the electron beam samples. When formulated to similar crosslink density, peroxide initiated cure and electron beam cure produced similar trends in physical properties.