Insight into the interactions of functionalised rubber-modified silica in tyre tread compounds

• Grafted rubber chains on silica create hybrid organic–inorganic reinforcing filler • Rubber-modified silica enhances reinforcement through an improved interphase. • Physical interfacial entanglements of silica-grafted chains reinforce vulcanisates. • Co-curing of grafted rubber chains is a key mechanism in rubber reinforcement. Silica plays a crucial role as a reinforcing component in rubbers, which are essential for high-performance tyres. Despite advances in conventional silica-silane coupling, challenges remain in achieving dynamic rubber-filler interfacial interactions. In this context, functionalised Solution Styrene-Butadiene Rubber (SSBR) was chemically coupled onto silica surface and applied as a reinforcing filler in model tyre tread compounds. This study investigates the impact of SSBR-modified silica, in the presence of varying quantities of a mono-functional covering agent, on the properties of the compounds. The complex interactions between rubber matrix, modified silica, and silane, were evaluated focusing on vulcanisation behaviour, filler dispersion, and reinforcement mechanisms. The anchoring of SSBR molecules onto the silica surface was found to enhance the vulcanisation reactivity, leading to a shorter scorch time and a faster cure rate, attributed to the hybrophobisation of silica surface by the grafted chains. The covering of the silica surface reduces the adsorption of accelerators which are then directly available for the vulcanisation process. Meanwhile, the covering silane plays a predominant role in reducing filler-filler interactions but does not provide chemical rubber-filler interaction. This study highlights that the grafted SSBR chains on the silica surface give improved reinforcement in rubber compounds, as they can entangle and co-cure with the rubber matrix. Results from a linear regression analysis demonstrate a strong correlation between swelling and cure torque difference, supporting the hypothesized co-crosslinking mechanism. The current approach requires further development to enhance its efficiency in reinforcing the compounds.