A Study of EPDM Devulcanization in a Co-rotating Twin-screw Extruder.

T he devulcanization process of EPDM compound was carried out using a twin-screw extruder. The effects of barrel temperature, screw speed and diphenyl disulphide as a devulcanization agent (DVA) on the devulcanization were investigated. Percent devulcanization, sol fraction, Mooney viscosity and curing behaviour of devulcanized samples were studied. The devulcanized samples could not cure without addition of the curing agents. After the addition of curing agents into the devulcanizates, the general behaviour of rheometry test for rubber compounds was observed. Percent devulcanization was dependent on DVA content and screw speed, especially at low and middle level of barrel temperature. Barrel temperature was the most effective parameter on the amount of sol fraction and Mooney viscosity. The devulcanizates were recured with a semi-efficient curing system. Tensile strength, elongation-at-break, compression set, hardness and cross-link density of revulcanizates were evaluated. It was found that the mechanical properties were slightly inferior compared to virgin compound.