Swelling of Filled Rubber Vulcanizates

Abstract

Abstract A detailed study has been made of the swelling of vulcanizates containing “adhering” and “non-adhering” fillers. The restriction of the swelling of vulcanizates containing “adhering” fillers compared to the swelling of the corresponding pure gum vulcanizate does not take place in solvents with solvent power below a critical value. The solvent power is indicated by the volume fraction of rubber (vr0) in the swollen pure gum vulcanizate. It appears that the critical value, vrc, is not very dependent on the type of black and slightly dependent on the crosslink density. Graphitized (2700° C) blacks differ from all other fillers in that they cause no restriction in swelling for any solvent, nor do they increase the swelling of the apparent matrix as is the case with non-adhering fillers. A semi-quantitative explanation for the observed phenomena is proposed.