DIE-SWELL OF CARBON-BLACK FILLED RUBBER COMPOUNDS

Die-swell of carbon black filled rubber compounds has been studied in terms of a model based on some generalizations of the results from linear viscoelasticity and on finite measure of strain. Butyl based compounds with four types of carbon black varying in surface activity and structure have been prepared for this purpose. Using capillary viscometer with a special optical unit, die-swell has been measured directly as a function of shear rate and carbon black content. Additionally, measurements of viscosity, Young's modulus and Poisson's ratio have been carried out in order to calculate the die-swell from the model. The measured and calculated die-swell values have been compared and, regarding simplifications of the model, fairly good agreement has been obtained. As for the die-swell itself, the main result is that it diminishes with increasing concentration of elastomer-filler linkages, i.e. with increasing both carbon black content and/or its surface activity.