Radiation Curing of Ethylene—Propylene—Diene Elastomers

Abstract

Abstract A significant reduction of the radiation dose required to cure EPDM elastomers can be obtained by introducing crosslinking monomers into the compounds. Multifunctional acrylates are more efficient than either allylic or pendent-vinyl crosslinking agents. The curing rate is also affected by the nature of the unsaturation in the base polymer. Compounds of EPDM containing 5-ethylidene-2-norbornene are more reactive than those with 1,4-hexadiene. Increasing polymer unsaturation levels above 3 per cent or changes in ethylene—propylene ratios have little effect. Curing rate is dependent, however, on the Mooney viscosity of the elastomer, with higher viscosities yielding faster cures. The addition of extender oils drastically reduces radiation efficiency, which depends on both the nature and the level of the oil. This can be overcome by increasing the monomer content. The physical properties of radiation-cured EPDM compare favorably with those of sulfur-cured EPDM. The radiation-cured EPDM exhibits greatly improved compression set and oil resistance.