Sustainable Reinforcement of Silicone Rubber: Comparative Analysis of Biosilica from Rice Husk and Conventional Silica

The objective of this study is to compare rice husk-derived silica (biosilica) synthesized via an environmentally friendly method with conventional silica (Zeosil 175) for reinforcing the mechanical properties of silicone rubber. The silanol group content of Zeosil 175 (9.45 OH/nm²) is higher than that of biosilica (7.07 OH/nm²), whereas the specific surface area of biosilica (159.52 m²/g) exceeds that of Zeosil 175 (144.90 m²/g). Silicone rubber specimens containing two types of silica nanoparticles were prepared at loading levels of 5, 10, 15, 20, 25, and 30 parts per hundred rubber to evaluate their mechanical properties and characteristics. Results indicate that silicone rubber filled with biosilica shows comparable tensile strength to Zeosil 175 at low filler contents, which can be attributed to its higher specific surface area. However, at higher loading levels, the mechanical properties are somewhat diminished due to the Payne effect and filler agglomeration resulting from the larger particle size of biosilica. These experimental findings offer insights into the potential utilization of rice husk-derived biosilica as an alternative to conventional silica in enhancing the properties of silicone rubber alongside the findings of the mechanical analysis.