CARBON-BLACK ELASTOMER INTERACTION-II - EFFECTS OF CARBON-BLACK SURFACE-ACTIVITY AND LOADING

Carbon black morphology, surface activity and loading have been varied systematically to study the effects on an SBR formulation. The surface activity of five commercial grades of carbon black was varied by heat treating the standard grade samples at 1100-degrees-C and 1500-degrees-C in an inert atmosphere. Measurements on carbon black-elastomer interaction were based on a parameter I, defined elsewhere.1 The parameter I exhibited the previously reported correlation with known indicators of the surface activity of carbon blacks. The heats of adsorption by inverse gas chromatography at infinite dilution have been found useful as a measure of the carbon-black surface energy related to rubber interaction. These measurements have been employed in conjunction with carbon-black morphology and loading to develop a surface-area-modified and a surface-energy-modified effective volume fraction V' and psi, respectively. The parameter V' was utilized to explain the variation of the dynamic elastic modulus E' at 1% double strain amplitude (DSA) for all rubber compounds. The parameter psi was used to explain the variation of E' at 25% DSA and the factor sigma in the calculation of I. The parameters V' and psi provide a model for the estimation of I from fundamental carbon-black morphological properties and surface energy.