Journal Papers Published by the Rubber Research Group
"Viscoelastic behaviour of rubber under a complex loading II: The effect of carbon black"
Journal: Journal of Applied Polymer Science, Vol. 117, 1290–1297 (2010)
Suphadon et al. (J. App. Poly. Sci., 2009, Vol. 113, p. 693.) showed using small oscillations of less than 1% strain superimposed on a larger pre-strain that the loss modulus, referred to the test piece dimensions after the application of the pre-strain, did not vary with pre-strain for unfilled rubber materials for a wide range of pre-strains up to 100%. Also for unfilled rubbers it was observed that up to 100% pre-strain that the loss modulus behaviour was isotropic. This paper extends this previous work to larger pre-strains for styrene butadiene rubber (SBR) compounds and natural rubber (NR) compounds some of which incorporate carbon black fillers. Both the storage modulus and the loss modulus are again calculated relative to the dimensions of the test piece after the application of the pre-strain. These results show that for materials with 25 phr of carbon black filler, the loss modulus was still independent of the pre-strain for normal engineering strains but at filler contents of 50 phr the loss modulus increases with pre-strain at extension ratios less than 2. Even so over the typical engineering strains of below 50%, the loss modulus was still independent of strain. This increase in loss modulus at large pre-strains can in part be explained by considering the molecular orientation of the polymer in combination with a consideration of the molecular slippage that takes place at the polymer filler interface.