Abstract: Polysulfide compounds and vulcanization compositions containing the polysulfide compounds, for use in vulcanizing rubbers, are disclosed, with the polysulfide compounds being of the formula ##STR1## wherein R.sup.1 -R.sup.4 are each, independently, hydrogen or C.sub.1 -C.sub.4 alkyl and n is 2 to 10wherein the polysulfide compounds can be used alone or in a vulcanization composition containing the polysulfide compound, sulfur, one or more additional accelerators, one or more basic compounds and, optionally, conventional rubber additives, to provide vulcanized products with improved reversion stability and ageing stability.

Abstract: An unsaturated, elastomeric ABC block copolymer comprised of the monomer units of 40 to 80% of 1,3-butadiene, 5 to 40% of isoprene and 2 to 30% of styrene, said copolymer comprising i) 40 to 75% of block A which contains styrene and butadiene units or isoprene and butadiene units with a content of distributed vinyl or isopropenyl groups of less than 15%, iia) up to 25% of a block B which contains styrene and butadiene units or isoprene and butadiene units with a vinyl or isopropenyl content of more than 70%, or iib) up to 25% of a block B' which contains styrene, isoprene and optionally butadiene units with a content of homogeneously distributed isopropenyl or vinyl groups of less than 15%, and iii) 20 to 55% of a block C which contains styrene and isoprene units and optionally butadiene units with an isopropenyl or vinyl content of more than 70%.

Abstract: An unsaturated elastomeric AB block copolymer comprising 20-75 wt. % 1,3-butadiene monomer units; 5-50 wt. % isoprene monomer units; and 3-30% wt. % styrene monomer units; wherein said block copolymer contains less than 3 wt. % styrene blocks, each of said block A and block B contain all three of said monomer units, said copolymer comprises 30-90 wt. % of block A and 70-10 wt. % of block B, and wherein the average vinyl and isopropenyl content of block B are each at least 30% higher than those of block A; and a method for preparing the unsaturated AB block copolymer.

Abstract: An unsaturated elastomeric AB block copolymer, comprising:(i) 45-85 wt. % 1,3-butadiene,(ii) 5-40 wt. % isoprene, and(iii) up to 30 wt. % styrene,wherein said AB block copolymer comprising:40-80 wt. % of a block A, said block A comprising butadiene monomer units and having a content of uniformly distributed vinyl groups of 8-60 wt. %, and60-20 wt. % of a block B, said block B comprising 0-60 wt. % 1,3-butadiene, at least 10 wt. % isoprene and up to 45 wt. % styrene monomer units, wherein the butadiene and isoprene monomer units have a vinyl group content of 75-90 wt. %.