A cable having one or more conductors surrounded by at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer, in that order, wherein the insulation layer is not crosslinked and has at least 90 wt % of a polymer composition, said polymer composition having: (I) 85.0 to 99.5 wt % of an LDPE; and (II) 0.5 to 15.0 wt % of an HDPE having a density of at least 940 kg/m.sup.3 or 1.5 to 15.0 wt % of an ultra-high molecular weight polyethylene having a Mw of at least 1,000,000.

A cable having one or more conductors surrounded by at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer, in that order, wherein the insulation layer is not crosslinked and has at least 90 wt % of a polymer composition, said polymer composition having: (I) 85.0 to 99.5 wt % of an LDPE; and (II) 0.5 to 15.0 wt % of an HDPE having a density of at least 940 kg/m.sup.3 or 1.5 to 15.0 wt % of an ultra-high molecular weight polyethylene having a Mw of at least 1,000,000.

A crosslinkable polymer composition includes an unsaturated polyolefin having a total amount of carbon-carbon double bonds/1000 carbon atoms of at least 0.1, at least one scorch retarder, and at least one crosslinking agent.

A crosslinkable polymer composition includes an unsaturated polyolefin having a total amount of carbon-carbon double bonds/1000 carbon atoms of at least 0.1, at least one scorch retarder, and at least one crosslinking agent.

A thermoplastic elastomer composition contains components (A), (B), (C), and (D), wherein the weight ratio of component (C) to component (D) is 0.1 and <2, component (A) is an ethylene random copolymer containing 50% and 90% of a monomer unit derived from ethylene by weight relative to the component (A) and a monomer unit derived from at least one monomer selected from the group consisting of -olefins having a number of carbon atoms of 3 and 10, component (B) is a polymer containing >50% and 100% of a monomer unit derived from propylene by weight relative to the component (B), component (C) is a copolymer containing an ethylene polymerization block and an ethylene--olefin copolymerization block, and component (D) is an ethylene polymer containing >90% and 100% of a monomer unit derived from ethylene by weight relative to the component (D).

A thermoplastic elastomer composition contains components (A), (B), (C), and (D), wherein the weight ratio of component (C) to component (D) is 0.1 and <2, component (A) is an ethylene random copolymer containing 50% and 90% of a monomer unit derived from ethylene by weight relative to the component (A) and a monomer unit derived from at least one monomer selected from the group consisting of -olefins having a number of carbon atoms of 3 and 10, component (B) is a polymer containing >50% and 100% of a monomer unit derived from propylene by weight relative to the component (B), component (C) is a copolymer containing an ethylene polymerization block and an ethylene--olefin copolymerization block, and component (D) is an ethylene polymer containing >90% and 100% of a monomer unit derived from ethylene by weight relative to the component (D).

A method comprising introducing a polymerization feed comprising an -olefin, a diluent, and a diene to a polymerization system, under polymerization conditions, whereby a polymer product is produced, wherein the diene is present at a level in the range of from about 1 ppm to about 1000 ppm based on the diluent.

A method comprising introducing a polymerization feed comprising an -olefin, a diluent, and a diene to a polymerization system, under polymerization conditions, whereby a polymer product is produced, wherein the diene is present at a level in the range of from about 1 ppm to about 1000 ppm based on the diluent.

A rubber composition comprising a nitroxide compound crosslinking agent containing 2.3 to 5.0 parts by weight of organic peroxide having a one-hour half-life temperature of 110 to 130 C., based on 100 parts by weight of an ethylene-butene-non-conjugated diene copolymer. Then, the ethylene-butene-non-conjugated diene copolymer can be used by being blended with EPDM in an amount of 50 wt % or less in the total amount of the ethylene-butene-non-conjugated diene copolymer and EPDM. A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition, having functions required as a sealing material for separators, and having improved low temperature sealing properties and scorch resistance as well as excellent injection molding properties.

A rubber composition comprising a nitroxide compound crosslinking agent containing 2.3 to 5.0 parts by weight of organic peroxide having a one-hour half-life temperature of 110 to 130 C., based on 100 parts by weight of an ethylene-butene-non-conjugated diene copolymer. Then, the ethylene-butene-non-conjugated diene copolymer can be used by being blended with EPDM in an amount of 50 wt % or less in the total amount of the ethylene-butene-non-conjugated diene copolymer and EPDM. A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition, having functions required as a sealing material for separators, and having improved low temperature sealing properties and scorch resistance as well as excellent injection molding properties.