Effect of Maleamic Acid on the Properties of Silicone Rubber/Silica Composites

Maleamic acid (MAA), hexamethyldisilazane (HDMS) and vinyltriethoxysilane (VTEO) were used to modify the silicone rubber (SR)/Silica composites. The effects of these three modifiers on the composites were compared using scanning electron microscopy (SEM), equilibrium swelling method and mechanical properties tests, etc. The results show that MAA can effectively facilitate the dispersion of silica in SR matrix and increase the crosslinking densities of SR/Silica composites. These can be ascribed to the special chemical structure of MAA. On the one hand, the carboxyl group and amino group of MAA are able to attach onto the surface of silica via hydrogen bonds to promote the dispersion of silica in SR matrix, and, as hydrogen-bond donors and receptors, enable the formation of a non-covalent crosslinking network. On the other hand, the carbon-carbon double bond in MAA might participate in the curing reaction of SR side chains, thus enhancing the interactions between silica and SR matrix. In comparison with SR/Silica/HDMS and SR/Silica/VTEO composites, MAA modified SR/Silica composites (m(MAA)∶m(SR)=3%) exhibited a tensile strength improvement of 24% and 52% higher, respectively. Besides, the lowest compression relaxation rate and compression set were also achieved by SR/Silica/MAA composites. We believe that MAA can be a good additive candidate for fabrication of high-strength silicone rubber.