Effect of carbon black and silica fillers in elastomer blends

The effects of carbon black and pyrogeneous silica fillers on the interfacial properties of a homopolymer [polybutadiene, (PB)] and a terpolymer [brominated poly(isobutylene-co-p-methylstyrene), (BIMS)] are reported. Neutron reflectivity (NR) was used to study the interfacial structure. The results are complemented by scanning transmission X-ray microscopy (STXM) and lateral force microscopy (LFM), which were used to probe the morphology and surface lateral force. Small-angle neutron scattering (SANS) was used to characterize the size and surface properties of the filler aggregates in elastomers. Our results show that the interfacial behavior of PB/BIMS is more sensitive to carbon black than to silica. The interfacial broadening is significantly slowed down with addition of merely φ_CB = 0.01 (volume fraction) carbon black fillers. This volume level is much lower than that used in bulk rubbers (φ_CB ≥ 0.1). Pyrogeneous silica has a less pronounced effect on the interracial characteristics. When both carbon and silica are incorporated into the PB layer, the effect of carbon black is offset by silica fillers.