Distribution ratio of carbon black in polyisobutyrene/polyisoprene rubber blends using high-resolution solid-state 13 C NMR

We attempted to estimate the distribution ratio of carbon black (CB) in blends of polyisobutyrene rubber and polyisoprene rubber using high-resolution solid-state 13 C nuclear magnetic resonance (NMR). Our NMR analysis revealed that, in polyisobutyrene rubber/polyisoprene rubber/CB composites, CB more easily distributes in polyisoprene rubber than in polyisobutyrene rubber. We found that more than 70% of CB is distributed into the polyisoprene rubber phase. The sum of the amounts of CB in both the polyisobutyrene rubber and polyisoprene rubber phases estimated by our method using 13 C NMR closely corresponds with the amount of CB originally added to the compound, verifying the validity of the NMR method. Further, we observed the distribution of CB in polyisobutyrene/polyisoprene rubber blends using transmission electron microscopy and the Carbon-Black-Gel method, which can only be used for unvulcanized rubber blends, for comparison. The results obtained using these three methods show similar tendencies, which confirms the accuracy of this method of using 13 C NMR to determine CB distribution in rubber blends.