The present disclosure provides a polyisoprene wherein: a vinyl bond content of the polyisoprene is 30 mol % or higher; and a ratio of the weight-average absolute molecular weight (Mw′) determined by GPC-MALS with respect to the weight-average molecular weight (Mw) in terms of polystyrene determined by GPC, i.e., Mw′/Mw, is 0850 or less. A rubber composition containing the polyisoprene is excellent in the fuel-saving performance and grip performance on a wet road surface, as compared with a rubber composition containing the conventional polyisoprene.

The present technology provides a rubber composition having: from 30 to 50 parts by mass of carbon black having a nitrogen adsorption specific surface area of from 100 to 130 m.sup.2/g, from 25 to 40 parts by mass of carbon black having a nitrogen adsorption specific surface area of from 37 to 60 m.sup.2/g, from 1.5 to 2.2 parts by mass of sulfur as a pure sulfur content, and from 110 to 200 mass % of a sulfenamide-based vulcanization accelerator relative to the pure sulfur content compounded in 100 parts by mass of diene rubber containing from 30 to 60 parts by mass of isoprene rubber and from 40 to 70 parts by mass of butadiene rubber.

A conjugated diene-based polymer of the present invention has an absolute molecular weight measured by viscosity detector-equipped GPC-light scattering measurement, of 40×10.sup.4 or more and 5000×10.sup.4 or less, has a branching number (Bn) measured by the viscosity detector-equipped GPC-light scattering measurement, of 8 or more, and has a modification ratio of 60% by mass or more.

The bead portion of a pneumatic tire has a bead structure including a bead core having a bead cord covered with a resin material, and a bead filler continuous to the bead core and formed of the resin material and tapered outside in the tire radial direction. The bead structure has a weld line of the resin material. The weld line is formed inside in the tire radial direction more than ⅔ of the total height along the tire radial direction of the bead structure.

The present invention relates to compositions for elastomeric compounds for tyres, comprising monotetrazole compatibilizing agents characterised by precise activation temperatures, tyre components and tyres for vehicle wheels which comprise them. Advantageously, the present monotetrazole compatibilizing agents allow the breaking properties of the compounds to be improved while maintaining a high compatibilisation of the filler.

Provided is a pneumatic tire with which the same driving safety as prior arts can be ensured and an improvement in fuel efficiency performance and durability performance is achieved. In this pneumatic tire, the tire radial direction outside end section of a chafer is disposed on the tire surface part, the loss tangent tan δ70° C.-SW of a side wall, the loss tangent tan δ70° C.-C of the chafer, complex elastic modulus E*70° C.-SW of the side wall, and the complex elastic modulus E*70° C.-C of the chafer under the condition of 70° C., an elongation of 1%, and a frequency of 10 Hz, and the loss tangent tan δ150° C.-SW of the side wall, and the loss tangent tan δ150° C.-C of the chafer measured under the condition of 150° C., an elongation of 1%, a frequency of 10 Hz satisfy the following expression. tan δ70° C.-SW+tan δ70° C.-C≤0.25|tan δ70° C.-SW−tan δ70° C.-C|≤0.07 E*70° C.-C−E*70° C.-SW≤6.5 MPa tan δ150° C.-SW+tan δ150° C.-C≤0.20

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 present invention relates to elastomeric compositions for tyres and relative compounds, components and tyres comprising them, said compositions comprising an elastomeric polymer, a phenolic product, optionally already partially cross-linked, optionally an aldehyde and/or at least a methylene donor product and an oxidised carbon allotrope as a cross-linking catalyst. Advantageously, this catalyst is able to complete the cross-linking reactions of the phenolic resins in the conventional times and conditions of vulcanisation, or even more rapidly, providing mechanically stable compounds.

The present invention is directed to a pneumatic tire having a tread comprising a vulcanizable rubber composition comprising, based on 100 parts by weight of elastomer (phr), up to 100 phr of a solution polymerized styrene-butadiene rubber; from 5 to 50 phr of a fatty acid monoester of formula 1

##STR00001##

where R.sup.1 is selected from C1 to C8 linear or branched alkyl, C1 to C8 linear or branched alkenyl, and C2 to C6 linear or branched alkyl substituted with from one to five hydroxyl groups; R.sup.2 is C11 to C21 alkyl or C11 to C21 alkenyl; from 5 to 50 phr of a hydrocarbon resin having a Tg ranging from −40° C. to 20° C.; less than 10 phr of a petroleum-derived oil; and from 50 to 130 phr of silica. optionally, from about 1 to 50 phr carbon black.

The invention relates to nano-particle containing rubber formulations having improved physical properties used for manufacturing cured rubber articles and more specifically to a rubber composition containing non-rubber masterbatch containing graphene comprised nanoparticles. Such compositions may be used for articles of manufacture that include, for example, conveyor belts, motor mounts, tubing, hoses, or tires or components thereof.