Structure–property relationships of silica/silane formulations in natural rubber, isoprene rubber and styrene–butadiene rubber composites

ABSTRACT The mechanical performance of natural rubber (NR), synthetic poly‐isoprene rubber (IR), and styrene–butadiene rubber (SBR) composites filled with various silica/silane systems is investigated. The results are analyzed by referring to micro‐mechanical material parameters, which quantify the morphological and structural properties of the polymer and filler network. These are obtained from fits with the dynamic flocculation model (DFM) describing the strongly nonlinear quasi‐static stress–strain response of filler‐reinforced elastomers as found from multihysteresis measurements of the investigated compounds. We focus on the reinforcement mechanisms of silica compounds with coupling and covering silane, respectively. The fitted material parameters give hints that the coupling silane provides a strong chemical polymer–filler coupling, which is accompanied by improved strength of filler–filler bonds for all three rubbers types. This may result also from the chemical coupling of short chains bridging adjacent silica particles. It implies larger stress values for the coupling silane and, in the case of NR and IR, a more pronounced “Payne effect” compared to the covering silane. In contrast, for SBR, the coupling silane delivers a lower Payne effect, which is explained by differences in the compatibility between rubber type and silane‐grafted silica surface. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48435.