Abstract: A curable halobutyl rubber/polyepihalohydrin rubber blend comprises a cure system consisting essentially of (a) sulfur, (b) sulfur accelerator, (c) zinc-containing promoter, (d) urea or urea derivative vulcanization accelerator and, optionally, (e) di- or tri-mercapto nonsulfur curative such as 2,4,6-trimercapto-1,3,5-triazine. The halobutyl rubber/polyepi-halohydrin rubber blends that are crosslinked with the cure system of this invention exhibit excellent scorch safety and cure rate, as well as a high degree of crosslinking, and are useful in the manufacture of tire inner tubes and inner liners.

Abstract: A pneumatic radial tire is provided with a tread having from 1 part by weight of hydrated amorphous fine-particle silica per 3 parts of carbon black tread reinforcing filler, to about 3 parts by weight of the silica to 1 part of the carbon black. The amount of silica present is preferably in the range from about 18 parts to about 50 parts by weight per 100 parts of natural or synthetic rubber. When such a tread is compounded with a mercaptosilane in which the mercapto group is reversibly blocked, the tread provides reduced rolling resistance without loss of traction. Such reduction in rolling resistance without loss of traction is not observed when the silica is not coupled with the mercaptosilane coupling agent.