Isobutylene elastomer compound optimization for winter tire tread applications

Use of brominated isobutylene-co-paramethylstyrene (BIMS) improves lab dynamic properties predictive of wet and winter traction of formulations modeling winter passenger tire treads. Statistically designed blends of SIMS with cis-polybutadiene (BR) and natural rubber (NR) were studied in silane-coupled, silica-filled compounds. SIMS elastomer use requires adjustments to the curative system. By reducing sulfur and/or accelerator levels, compound cure and mechanical properties can be maintained. Winter and wet traction and handling properties were measured for retreaded winter tires containing BIMS/NR/BR blends in the model winter tread. Performance was evaluated by independent tire testing labs for tires having three different levels of SIMS used in place of NR. Results were compared to tires with a solution-polymerized styrene-butadiene rubber/NR/BR model tread used as control, and to a commercial winter tire tread compound used as a reference. Vehicles having tires with SIMS winter treads showed reduced braking distances on an indoor ice surface, on a snowy glacier in Austria, on a wet asphalt surface, and on a dry surface compared to both the control and reference winter treads. The 20-phr SIMS tread had a 76,000-kilometer projected wear-out life based on road testing in the winter in the U.S.