Degradation and cross-linking of ethylene-propylene copolymer rubber on reaction with maleic anhydride and/or peroxides

The reaction of EPR with dicumyl peroxide at 180°C or t‐butyl perbenzoate at 140°C resulted in the formation of a fraction insoluble in cyclohexane at 22°C. The presence of maleic anhydride (MAH) in the EPR‐peroxide reaction mixture increased the amount of insoluble polymer, whose concentration decreased as the peroxide concentration increased. The [η] of the cyclohexane‐soluble polymer decreased and the MAH content increased as the peroxide concentration increased at constant MAH concentration. The [η] and the MAH content of the soluble polymer increased as the MAH concentration increased at constant peroxide concentration. The EPR‐peroxide and EPR‐MAH‐peroxide reaction products were soluble in refluxing xylene and could be fractionated by precipitation with acetone. The presence of stearamide in the EPR‐MAH‐peroxide reaction mixture decreased the amount of cyclohexane‐insoluble polymer, indicative of decreased cross‐linking, but the [η] of the soluble EPR‐g‐MAH increased, indicative of decreased degradation, analogous to the effect of stearamide in the MAH‐peroxide reactions with LDPE and PP, respectively.