Fatigue, resilience and hardness properties of unfilled SMR L/ENR 25 and SMR L/SBR blends

The fatigue, resilience and hardness properties of natural rubber/epoxidize d natural rubber (SMR L/ENR 25) and natural rubber/styrene-butadiene rubber (SMR L/SBR) blends were studied with a blend ratio from 0 to 100% rubber. A semi-efficient vulcanization system was used throughout the study. The cu re rime of the rubber compound was determined by using the Moving-Die Rheom eter (MDR 2000). The fatigue life of the unaged and aged samples was determ ined by using a Fatigue To Failure Tester (FTFT), whereas the unaged sample s of resilience and hardness were measured by a Wallace Dunlop Tripsometer and a Wallace Dead Load Hardness Tester, respectively. Results indicate tha t before ageing, fatigue life passes through a maximum at 50% ENR and SBR f or both blends. This observation is attributed to the "synergistic'' effect of mutual reinforcement due to strain-induced crystallization in the forme r system, whereas for the latter system, compatibility accounts for the obs erved maximum. Ageing lowers the fatigue life for both blends, a phenomenon which is associated essentially with the breakdown of crosslinks. Resilien ce decreases with increasing blend ratio, whereas the reverse behaviour is observed for the hardness experiment. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.