In some embodiments, the present disclosure provides a composition comprising from 5 phr to 30 phr of a PEDM terpolymer having 1 to 10 wt % diene, 13 to 40 wt % ethylene, and 15 to 85 wt % propylene, based on the weight of the PEDM terpolymer. The composition further comprises from 70 phr to 95 phr of an ethylene-based copolymer comprising an ethylene content different than the first polymer, a C.sub.3 to C.sub.12 -olefin, and, optionally, one or more dienes.

A power transmission belt is at least partially formed of a rubber composition. The rubber composition contains a rubber component, cellulose nanofibers, and carbon black. The amount of the cellulose nanofibers to be added is from 0.1 parts by mass to 20 parts by mass, relative to 100 parts by mass of the rubber component. The amount of the carbon black to be added is from 5 parts by mass to 80 parts by mass, relative to 100 parts by mass of the rubber component. The sum of the amount of the carbon black to be added and three times the amount of the cellulose nanofibers to be added is from 15 to 90.

A power transmission belt is at least partially formed of a rubber composition. The rubber composition contains a rubber component, cellulose nanofibers, and carbon black. The amount of the cellulose nanofibers to be added is from 0.1 parts by mass to 20 parts by mass, relative to 100 parts by mass of the rubber component. The amount of the carbon black to be added is from 5 parts by mass to 80 parts by mass, relative to 100 parts by mass of the rubber component. The sum of the amount of the carbon black to be added and three times the amount of the cellulose nanofibers to be added is from 15 to 90.

A power transmission belt or hose or other dynamic article with an elastomeric body comprising a rubber composition that includes an ionomeric polymer additive, such as an ethylene-methacrylic acid copolymer or a butyl ionomer. The rubber body exhibits improved crack growth resistance over the same body composition without the ionomer additive.

A power transmission belt or hose or other dynamic article with an elastomeric body comprising a rubber composition that includes an ionomeric polymer additive, such as an ethylene-methacrylic acid copolymer or a butyl ionomer. The rubber body exhibits improved crack growth resistance over the same body composition without the ionomer additive.

A power transmission belt is at least partially formed of a rubber composition. The rubber composition contains a rubber component, cellulose nanofibers, and carbon black. The amount of the cellulose nanofibers to be added is from 0.1 parts by mass to 20 parts by mass, relative to 100 parts by mass of the rubber component. The amount of the carbon black to be added is from 5 parts by mass to 80 parts by mass, relative to 100 parts by mass of the rubber component. The sum of the amount of the carbon black to be added and three times the amount of the cellulose nanofibers to be added is from 15 to 90.

A power transmission belt is at least partially formed of a rubber composition. The rubber composition contains a rubber component, cellulose nanofibers, and carbon black. The amount of the cellulose nanofibers to be added is from 0.1 parts by mass to 20 parts by mass, relative to 100 parts by mass of the rubber component. The amount of the carbon black to be added is from 5 parts by mass to 80 parts by mass, relative to 100 parts by mass of the rubber component. The sum of the amount of the carbon black to be added and three times the amount of the cellulose nanofibers to be added is from 15 to 90.

A power transmission belt includes a cured product of a rubber composition containing a rubber component containing an ethylene--olefin elastomer, an ,-unsaturated carboxylic acid metal salt, magnesium oxide, organic peroxide and inorganic filler. A proportion of the magnesium oxide is 2 to 20 parts by mass per 100 parts by mass of the rubber composition and is 5 parts by mass or more per 100 parts by mass of the ,-unsaturated carboxylic acid metal salt.

A power transmission belt includes a cured product of a rubber composition containing a rubber component containing an ethylene--olefin elastomer, an ,-unsaturated carboxylic acid metal salt, magnesium oxide, organic peroxide and inorganic filler. A proportion of the magnesium oxide is 2 to 20 parts by mass per 100 parts by mass of the rubber composition and is 5 parts by mass or more per 100 parts by mass of the ,-unsaturated carboxylic acid metal salt.

Provided is a desulfurized rubber capable of producing a crosslinked rubber having an excellent mechanical strength. The desulfurized rubber contains a solvent-soluble rubber component A having a weight-average molecular weight of more than 260,000 and less than 600,000, and a solvent-insoluble rubber component B, wherein the content ratio of the rubber component B is less than 45% by mass of the total mass of the content a of the rubber component A and the content b of the rubber component B.