Compositions comprising mono-olefin polymers and hydrogenated block copolymers

Polymer blends comprise (1) a hydrogenated block copolymer of the formula A-B-A in which each A, prior to hydrogenation, is a polymer of an alkenyl aromatic hydrocarbon having an average molecular weight of 4000 to 115,000 and in which B, prior to hydrogenation, is a polymerized conjugated diene having an average molecular weight of 20,000 to 450,000, polymer A constituting 2 to 33% of the block copolymer, the residual unsaturation in both the aromatic and aliphatic blocks being less than 30% of the original value, and (2) an alpha-olefin polymer having a molecular weight of at least 5000. The hydrogenated block copolymers may be obtained as described in Specification 1,020,709. The blends may be either thermoplastic or elastomeric depending upon whether they contain major or minor proportions of polyolefins. The examples describe making blends of polyethylene and polypropylene with polystyrene-polyisoprene-polystyrene block copolymers.