Effect of crosslink density on solubility parameters of styrene butadiene rubber and the application in pre-screening of new potential additives

Equilibrium swelling measurement and software program were employed to investigate the effect of crosslink density on the swelling responses and three-dimensional solubility parameters (HSP) of the cured SBR samples. The swelling responses change evidently with increased crosslink densities which, however, have no influence on the HSP values of SBR. In order to study the application of HSP in predicting interactions between rubbers and additives, a set of new Flory-Huggins interaction parameters (χHSP) was calculated by HSP values, and was further correlated with the correlation index, which was obtained by normalizing the swelling data. The results showed that the swelling ratio decreased linearly with increasing χHSP value. The slope of these linear relations obtained for each SBR group decreased with increasing crosslink density in the form of power function. On the contrary, the relationship obtained between the correlation index and χHSP value had no change with the crosslink density. Taking advantage of this study, one can easily make the pre-screening of potential additives for their suitability in the rubber formula design. •The effect of crosslink density on swelling responses and solubility parameters have been investigated systematically.•The change of swelling responses with crosslink density has been determined quantitatively.•New Flory-Huggins interaction parameter (χHSP) has been calculated with HSP values.•The relationship of correlation index and χHSP value has been established by considering crosslink density.•The pre-screening work of potential additives for formula design becomes more conveniently now.