Network formation at squalean/Vinyl-containing silica interfaces

Abstract

This work reports an alternative approach to forming crosslinked network at the “interphase” between natural rubber and silica. The model studies involved chemical modification of silicon oxide surface (a flat surface model for silica) by vinyl-containing silane reagents followed by a reaction with squalene (a natural rubber model). Silicon oxide surfaces containing a monolayer of vinyldimethylsilyl and trivinylsilyl groups were capable of forming interfacial network with squalene as opposed to its saturated analog, squalane, when p-toluenesulfonic acid was used as a catalyst. A comparative study indicated that the crosskinked network can also be generated at vinyl-containing silicon oxide/squalene interface in the presence of a conventional sulfur curing agent. The model studies have demonstrated that the thickness of the crosslinked network can be primarily controlled by reaction time and temperature. The thickness and the rate of crosslinked network formation were independent of vinyl group density on silicon oxide surface. The results of curing behavior and mechanical properties of natural rubber composites filled with vinyl-containing silica agree well with the results of model studies. It is thus feasible to use vinyl-containing silica as an alternative reinforced filler for natural rubber, particularly when it was used in a combination with a silane coupling agent such as bis(triethoxy silyl propyl tetrasulfide).