Analysis of the Fatigue Process in NR/BR Blends

Mechanism of improvement of the fatigue resistance by blending poly(butadiene) (BR) to natural rubber (NR) was investigated. In this study, the changes of tensile property of NR/BR blends and NR during the dynamic deformation were examined. The following results were obtained by Ahagon plot of tensile property results (λ_b=AM₁₀₀ ^-0.75)

Dynamic deformation induced enhanced crosslinking to the vulcanizates of NR and NR/BR blends. The rates of crosslinking and main chain scission during the  dynamic deformation were evaluated by means of the tensile property changes of samples after the dynamic deformation. The relationship between the extents of crosslinking and main chain scission suggested that the faster scission caused the faster crosslinking. The acceleration of crosslinking was due to the mechanochemical reactions where the main chain scission by the deformation generated radicals which in turn of accelerate crosslinking via autoxidation. Blending BR to NR made the fatigue life longer and the rate of crosslinking slower. The close relationship was found between the fatigue life and the rate of crosslinking during the dynamic deformation.