Constructing a Covalently Cross-Linked Particle–Matrix Interface to Reinforce the Performance of Liquid Silicone Rubber

In nanosilica particle modification processes with hydrolysis of silane coupling agents, the hydrolysates are prone to undergo condensation. The condensed species graft onto particle surfaces and induce particle agglomeration, which results in poor particle dispersion. Furthermore, the reinforcing effect of silica in silicone rubber is limited by hydrogen bonding and van der Waals forces at the particle–matrix interface, yielding suboptimal enhancement. This paper proposes a modification route involving complete hydrolysis of the silane coupling agent prior to grafting, establishing a modification process of “acidic hydrolysis–slurry mixing–spray drying–thermal reaction”. Octenyltrimethoxysilane (VOTMS) bearing a double bond and octyltrimethoxysilane (OTMS), which possess comparable modifier structures, were employed for isolating the role of the double bond. They were hydrolyzed and grafted under individually optimized conditions to achieve similar grafting densities on the particle surfaces and similar dispersion of the modified particles within the silicone rubber. The double bonds of VOTMS grafted on the particle surface are linked with the double bonds of the side chains of silicone rubber with a cross-linking agent through an addition reaction, forming an interface of a covalent bond cross-linking network. This significantly increases the cross-linking density, tensile strength, and thermal stability of silicone rubber, demonstrating that the covalent cross-linking network formed at the particle–matrix interface substantially improves the reinforcing performance of the silicone rubber.