VULCANIZATION OF ULTRASONICALLY DEVULCANIZED SBR ELASTOMERS

Sulfur cured SBR elastomers, devulcanized by high power ultrasonic irr adiation, were revulcanized by using the same curing conditions as for Virgin SBR. Crosslink density and gel fraction of virgin, devulcanize d, and revulcanized elastomers were measured. Curing behavior of some model compounds based on virgin and devulcanized SBR was investigated. Strongly pronounced differences between the curing behavior of virgin and devulcanized elastomers were observed. Torque and DSC studies ind icate that. two different processes during the crosslinking of devulca nized rubber take place. The existence of these two processes is expla ined by crosslinking of sulfidized polymer chains followed by crosslin king due to the presence of sulfur and accelerator. Chemical differenc es between virgin and devulcanized elastomers, explaining the observed phenomena, are discussed.