Tire black sidewall surface discoloration and non-staining technology: A review

The tire black sidewall is the outer surface that protects the casing again st weathering. It is formulated for resistance to weathering, oz;one aging, abrasion, tearing and cracking, and far good fatigue life by using blends of natural rubber and cis-butadiene rubber. Protection against ozone aging is of particular interest since reaction with these olefinically unsaturate d elastomers results in polymer decomposition via chain scission. Use of N- alkyl, N'-aryl-para-phenylenediamine antiozonants has proved most effective . However, their use also results in a surface discoloration, and thus they can be used in only limited amounts when tire appearance is also an import ant factor. A review is made of the literature describing this surface disc oloration problem and approaches to formulate a black sidewall compound to eliminate this surface discoloration upon exposure to ozone. Methods includ e use of non-staining antiozonants, and uses of elastomers with saturated b ackbones such as ethylene-propylene-diene terpolymers, halobutyl rubbers an d brominated-isobutylene-co-para-methylstyrene.