| 摘要 |
A chafer element for a pneumatic tyre comprises a strip of natural or synthetic rubbery material, which may be fabric reinforced, compounded with 60 to 110 parts of silica per 100 parts by weight of rubber hydrocarbon to yield a Williams plasticity Y-3 value of at least 6 when tested at 212 DEG F. under a 5 kilogram load for 3 minutes. Such rubbery material resists flow during vulcanization of the tyre and ensures an adequate rubber covering of the carcase plies in the bead area. Suitable synthetic base-rubbers include copolymers of butadiene and styrene, butadiene and acrylonitrile, isobutylene and isoprene, and rubbery polymers of chlorobutadiene. The compound may include up to 60 parts of carbon black, with the usual vulcanizing agents, antioxidant, and accelerators. Suitable accelerators include the thiazoles, dithiocarbamates, thiuram sulfides, aldehydeamines and guanidines, and for polychloro-butadiene rubbers, magnesium oxide. The compound is preferably mixed in three stages, the majority of the silica being added in the first two stages, and the remainder, if any, of the silica, together with the carbon black and vulcanizing agents being added at the final stage, the batches resulting from each stage being allowed to cool before proceeding to the next. The Specification describes a specific example of a suitable compound. |
