Abstract
Carbon black and cryogenically pulverised polyester polyurethane foam particles of average size 200μm were introduced alone and blended into natural rubber formulations to assess their affect on mechanical properties. Vulcanisates containing either carbon black or polyurethane particles showed maximum reinforcement at 60 and 30 parts per hundred rubber (pph) respectively. Directly comparing 30 pph filler loading, polyurethane particles showed similar ultimate strength but improved elastic properties compared with carbon black. Varying blend ratios of the two additives showed that the optimum addition concentration for balanced properties was equivalent to the addition of the optimum concentrations of each additive when incorporated alone i.e. 60 pph carbon black and 30 pph polyurethane particles. Whilst ultimate strength reduced ≈15% (compared with 60 pph carbon black alone), modulus reduced and substantial improvements in breaking strain and elongation set were observed, i.e. a small reduction in ultimate stress was accompanied by significant improvements in elastic properties.
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