Thermo‐oxidative aging in surface layer of cis‐1,4‐polybutadiene vulcanizates

The structural changes occurring in the surface layer and in the center bulk of butadiene (BR) vulcanizates has been studied in hot air at 120-180°C. The thermo-oxidative aging takes place only in the surface layer. The thickness of the oxidized surface layer is almost independent on the aging time after a period of aging time, but decreases with an increase of aging temperature. The crosslink on oxidation in the surface layer of BR vulcanizates increases with aging time, while the thermo-cyclization is formed in the center bulk