Plasma treatment of rice husk ash for application in tire retread compounds based on natural rubber

In this study, various plasma treatment protocols were employed to modify white rice husk ash (WRHA) for enhanced compatibility as a reinforcing filler in natural rubber (NR) formulations. The treatments included argon (cleaning), oxygen (activation), and acetylene (polymerization) plasma, aiming to increase WRHA's specific surface area. In this sense, five rubber compounds based on a standard NR/silica tire tread formulation were developed and assessed for vulcanization kinetics and mechanical, dynamical, and tribological properties. Characterization of the modified filler indicated a notable decrease in surface free energy, improving its dispersion and interaction with the NR matrix. While most modifications did not significantly affect vulcanization parameters or mechanical properties, argon plasma-treated WRHA hindered vulcanization and weakened the vulcanizates. However, all plasma treatments increased abrasion resistance and lowered tan δ values at 60°C and 100°C, indicating improved rolling resistance and reduced heat generation. Notably, WRHA treated with argon plasma followed by acetylene plasma polymerization exhibited the highest wet grip strength (~44%), along with reduced friction and wear (~14%). These findings suggest that plasma treatment, particularly the two-step method, offers a promising approach for enhancing filler surface properties in rubber compounds, leading to improved product durability. Highlights: White rice husk ash (WRHA) was successfully modified by plasma treatment. Argon treatment followed by acetylene plasma polymerization was the most effective approach. The incorporation of plasma-treated WRHA resulted in lower wear track compounds. Low rolling resistance and heat generation were achieved using plasma-treated WRHA. Plasma treatment emerges as an alternative to chemical rubber-filler compatibilization.