Effect of Bromination on the Properties of Ethylene-Propylene-Diene Rubber in the Presence of Divinylbenzene

Abstract

Abstract The curing behavior and vulcanizate properties of EPDM and brominated EPDM (BEPDM) were compared using a dicumyl peroxide curing system. The BEPDM displayed lower torque and crosslink density, but better tensile properties than the EPDM. In the presence of divinylbenzene (DVB) coagent, all vulcanizates, i.e., EPDM, BEPDM, and their blends with natural rubber, had improved tensile properties. At low DVB concentration, the filler effect of DVB on the modulus enhancement was noticed. At high and comparable DVB concentration, both the BEPDM and NR/BEPDM blend showed significantly higher modulus (M100) and tensile strength than their EPDM counterparts. The BEPDM was also found to have higher crosslink density and storage modulus (E′) than the EPDM. This observation could be attributed to the better dispersion of DVB in the BEPDM and NR/BEPDM vulcanizates, as supported by TEM measurements. The TEM data is also consistent with the properties observed on the uncured mixes, in which the NK/BEPDM + DVB mix has favorable viscosity and die swell properties due to the more homogeneous DVB dispersion in the rubber phases. Thus, the bromination of EPDM has resulted in better processing and vulcanizate properties of the rubber and its blend with natural rubber.