The reaction of sulphur and sulphur compounds with olefinic substances. Part VI. Factors influencing cyclic sulphide formation in the reaction of sulphur with polyisoprenes

Cyclic sulphides arc to a large extent secondary products of the reaction of primarily‐formed intermolecular polysulphides with polyisoprene hydrocarbon, and undue prolongation of the time of reaction of sulphur with polyisoprenes favours cyclic sulphide formation and so reduces the cross‐linking efficiency of the sulphur. Various accelerating substances markedly increase the cross‐linking efficiency either by permitting shorter reaction times to be employed, or by promoting a cross‐linking rather than a cyclizing reaction of the sulphur. Thiuram disulphide accelerators in the absence of sulphur bring about cross‐linking, the linkages being of C‐S‐C type rather than C‐C.