The effects of filling method on silicone rubber composites filled with SiO2 and TiO2

Abstract

Silica (SiO₂) serves as a reinforcing filler, while titanium dioxide (TiO₂) functions as a functional filler, imparting exceptional mechanical strength and UV resistance to silicone rubber. However, compatibility issues may arise when both fillers are incorporated into silicone rubber. This study explores potential solutions through processing methods, specifically by comparing the effects of graded filling and mixed filling on the properties of silicone rubber. Field emission scanning electron microscopy reveals that the mixed filling method promotes a more uniform dispersion of fillers, leading to enhanced performance. Curing tests indicate that the effect of the filling method on the curing processing performance of silicone rubber is negligible. Tensile test results reveal that, compared to the graded filling system, the mixed filling system improves the tensile strength and elongation at break of the silicone rubber composites by 13% and 13.4%, respectively, while simultaneously reducing the Mullins effect, thereby enhancing material stability. Thermogravimetric analysis (TGA) and differential thermal analysis (DTG) results indicate that the uniform dispersion achieved through mixed filling optimizes thermal transfer pathways, resulting in superior thermal stability compared to graded filling. Ultraviolet (UV) spectroscopy results demonstrate that composites containing added TiO₂ exhibit almost zero transmittance in the UV range of 200-400 nm, underscoring their excellent UV resistance; the mixed filling method provides superior UV protection compared to the graded fill method. In summary, for the dual-filler system of SiO₂ and TiO₂, the mixed filling approach enhances filler compatibility by improving dispersion, thereby elevating material performance and broadening potential applications.