A rubber-steel cord composite according to an embodiment is formed by vulcanizing and bonding a rubber composition containing 1 to 10 parts by mass of sulfur, 0.1 to 5 parts by mass of N,N-dibenzylbenzothiazole-2-sulfenamide, and 0.1 to 5 parts by mass of either one or both of hexamethylene bis-thiosulfate disodium salt dihydrate and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, with respect to 100 parts by mass of diene rubber containing natural rubber, and a steel cord. A pneumatic tire according to an embodiment includes the rubber-steel cord composite.

A rubber-steel cord composite according to an embodiment is formed by vulcanizing and bonding a rubber composition containing 1 to 10 parts by mass of sulfur, 0.1 to 5 parts by mass of N,N-dibenzylbenzothiazole-2-sulfenamide, and 0.1 to 5 parts by mass of either one or both of hexamethylene bis-thiosulfate disodium salt dihydrate and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, with respect to 100 parts by mass of diene rubber containing natural rubber, and a steel cord. A pneumatic tire according to an embodiment includes the rubber-steel cord composite.

The purpose is to provide rubber compositions and pneumatic tires which have reduced changes in tan δ peak temperature over time. The present invention relates to rubber compositions containing at least one copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, the rubber compositions having a heat aging resistance index defined by equation (1) of 0.45 or less.

The purpose is to provide rubber compositions and pneumatic tires which have reduced changes in tan δ peak temperature over time. The present invention relates to rubber compositions containing at least one copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, the rubber compositions having a heat aging resistance index defined by equation (1) of 0.45 or less.

An electro-conductive member for an electrophotographic image forming apparatus for which a change in resistance value is small even when a large current is applied at a high voltage for a long period of time is provided. The electro-conductive member includes a support having an electro-conductive outer surface and an electro-conductive layer on the outer surface of the support, in which the electro-conductive layer has a matrix including a cross-linked product of a first rubber and domains dispersed in the matrix, the domains include a cross-linked product of a second rubber different from the first rubber and an electrically conductive agent, and the cross-linked product of the second rubber has, in a molecule, a structural unit represented by Structural Formula (I).

[—(CH.sub.2).sub.n—O—]  Structural Formula (I)

In Structural Formula (I), n is an integer of 1 to 3.

An electro-conductive member for an electrophotographic image forming apparatus for which a change in resistance value is small even when a large current is applied at a high voltage for a long period of time is provided. The electro-conductive member includes a support having an electro-conductive outer surface and an electro-conductive layer on the outer surface of the support, in which the electro-conductive layer has a matrix including a cross-linked product of a first rubber and domains dispersed in the matrix, the domains include a cross-linked product of a second rubber different from the first rubber and an electrically conductive agent, and the cross-linked product of the second rubber has, in a molecule, a structural unit represented by Structural Formula (I).

[—(CH.sub.2).sub.n—O—]  Structural Formula (I)

In Structural Formula (I), n is an integer of 1 to 3.

A natural rubber composition includes a base resin including natural rubber, a filler including carbon black and silica, and an additive. The carbon black has a diameter of 20 nm to 50 nm, and the silica has a surface area of 100 to 150 m.sup.2/g. The additive includes at least one of a coupling agent, an activator, a crosslinking agent, an accelerator, or an anti-aging agent.

A natural rubber composition includes a base resin including natural rubber, a filler including carbon black and silica, and an additive. The carbon black has a diameter of 20 nm to 50 nm, and the silica has a surface area of 100 to 150 m.sup.2/g. The additive includes at least one of a coupling agent, an activator, a crosslinking agent, an accelerator, or an anti-aging agent.

A natural rubber composition includes a base resin including natural rubber, a filler including carbon black and silica, and an additive. The carbon black has a diameter of 20 nm to 50 nm, and the silica has a surface area of 100 to 150 m.sup.2/g. The additive includes at least one of a coupling agent, an activator, a crosslinking agent, an accelerator, or an anti-aging agent.

The present invention is directed to a sulfur vulcanizable rubber formulation comprising 10 phr to 100 phr of at least one partially saturated elastomer comprising repeat units, wherein at most 10% of all repeat units of the elastomer comprise a double bond; 0 phr to 90 phr of at least one diene based elastomer; 40 phr to 200 phr of at least one filler; and 5 phr to 70 phr of at least one hydrogenated plasticizer. This sulfur vulcanizable rubber formulation has been found to be useful in manufacturing tires.