Sustainable filler from agricultural waste: Ball milling optimization of rice husk ash‐based silica for green tire tread composites

Abstract The objective of this study was to investigate the potential of using rice husk ash‐derived silica (RHA‐SiO₂) as a sustainable reinforcing agent for tread rubber composites. This investigation addresses the dearth of systematic research on the mechanical ball milling of RHA‐SiO₂ by employing a central composite design within the response surface methodology to meticulously examine the impact of ball milling rotational speed, duration, and sample drying conditions on particle quality post‐milling. The study's findings indicate that the rotational speed exerts the greatest influence on RHA‐SiO₂ particle size, while drying state also emerges as a crucial factor influencing particle dispersion. The optimal ball milling parameters were identified as 240 r/min for 2 hours under anhydrous ethanol wetting conditions. Furthermore, it was demonstrated that RHA‐SiO₂ could preserve the hardness and density of the composite, while simultaneously enhancing its stiffness and resilience by replacing industrial silica in the reinforced tread rubber composite. Notably, a 50% substitution rate resulted in a 23.1% enhancement in tear strength, demonstrating the efficacy of RHA‐SiO₂ in bolstering the mechanical properties of rubber composites. Indeed, this work may offer new ways of high value use of agricultural waste and open new horizons for the development of high performance environmentally friendly tyre materials. Highlights RSM was utilized as a RHA‐SiO 2 ultrafine ball milling technique with controlled particle size. The optimum ball milling process was 240 r/min for 2 h in the alcoholic state. RHA‐SiO 2 exhibited a crystal structure and surface functional groups similar to the industrial silica. Replacement of industrial silica by RHA‐SiO 2 improved the mechanical properties of tread rubber composites. RHA‐SiO 2 at 50% substitution ratio increased tear strength by 23.1% to 41.76 kN/m.