Continuous devulcanisation by shear-flow stage reaction control technology for rubber recycling. Part 4. Devulcanisation mechanism for EPDM

Abstract

The mechanism of devulcanisation by shear flow stage reaction control technology for sulphur vulcanised EPDM rubber has been studied based on network structure of devulcanised rubber and the behaviour of crosslinking bond breakage. Sulphur crosslinking bonds of vulcanised rubber are broken selectively during the devulcanisation reaction. There are three types of crosslinking bonds such as monosulphide, disulphide and polysulphide bonds. At the initial stage of reaction, the polysulphide and disulphide bonds are changed to monosulphide bonds by heat. Furthermore, the monosulphide bond is broken by addition of shear stress and finally the devulcanised rubber is obtained. Residual sulphur atoms at the broken crosslinking bonds are stabilised by the reaction of the adjacent hydrogen atom and change into less reactive sulphur functional groups.