Dispersion of modified fumed silica in elastomeric nanocomposites

Surface modification of silica can enhance dispersion in elastomers by improved filler/polymer interactions. Surface modification is usually achieved with silane coupling agents.  It is also possible to deposit carbon directly during pyrogenic synthesis.  Carbon coated and chemically modified pyrogenic silica fillers were dispersed in styrene-butadiene (SBR) rubber to explore their differences. Surface carbon content, the extent of dispersion, and rheological properties were explored. X-ray scattering indicated that the in-flame and chemically modified fillers displayed good dispersion in the SBR matrix as quantified by the second viral coefficient_. Pristine pyrogenic silica aggregates at concentrations above a critical value display correlations in nanocomposites due to the presence of silanol groups on the surface as demonstrated in our previous work. In the present study, flame synthesized fumed silica with sufficient surface carbon monolayers mitigate the charge repulsion due to silanol moieties, removing aggregate correlations. This led to improved properties.  The rheological behaviour of the nanocomposites displayed a balance between lower rolling resistance and enhanced wet grip. Variations in the dispersion and its impact on rheological properties were also explored.