Experimental
Four different rubbers, which are widely used in tyre manufacturing, were studied. Synthetic 97% cis-1,4-polyisoprene was obtained from Sigma–Aldrich. Natural rubber (SMR 20) was sourced from Continental Tyre SA, while the 97% cis-polybutadiene rubber (Neodene 40) and the cold emulsion polymerised styrene- butadiene random copolymer (Afpol 1500, 23.5% styrene) were both procured from a local rubber manufacturer (Karbochem Pty Ltd). All of the rubbers were cryogenically milled in order to obtain a particle size below 1 mm, but other than that were used as received.