STATES OF CARBON-BLACK DISPERSION AND EXTENSIBILITY OF RUBBERS

Analysis is made for the origin of the mixing-induced tensile properly variation of a filled rubber. Attention is paid to the hydrodynamic effect f(phi(e)) of the filler, defined here as the factor to adjust the deviation of 100% modulus from the theory of rubber elasticity. For the rubbers mixed under variety of conditions, the f(phi(e))'s are calculated from the observed values of the modulus, at 25-degrees-C and 100-degrees-C, and the crosslink density. The variation of the f(phi(e)) is considered to be governed by the mobility of the polymer confined in agglomerates of the filler. The mobility variation due to mixing seems to be mainly influenced by agglomerate size at 25-degrees-C, and by agglomerate size and chemical constraints at 100-degrees-C. Therefore, the f(phi(e))'s at the two temperatures are suggested to be useful measures of the state of carbon-black micro-dispersion. The extensibility of the rubbers is closely related to f(phi(e)). This indicates that the failure property is also governed by the mobility of the confined polymer.