A facile ball milling method to produce sustainable pyrolytic rice husk bio-filler for reinforcement of rubber mechanical property

[Display omitted] •Pyrolytic rice husk (PRH) containing biochar and silica acted as a hybrid filler.•Biochar and silica were cross-linked and showed synergistic effect in rubber matrix.•Influence of ball milling on physicochemical properties of PRH was investigated.•Ball milling significantly improved the reinforcing performance of PRH. The hybrid fillers were reported to exhibit remarkable reinforcement in the mechanical properties of rubber composites. Herein, the pyrolytic rice husk (PRH) containing biochar and silica content was used as a natural hybrid filler, and exploited as a sustainable substitute for carbon black and commercial silica. The biochar and silica of PRH were cross-linked via Si-O-C bond and developed synergistic effect in rubber matrix, leading to the better reinforcement than the single component filler. Moreover, the influence of ball milling parameters on the physiochemical characteristics of PRH and the filler reinforcement of natural rubber vulcanizates were investigated. The results revealed that the changes of PRH in particle size, pore structure and surface chemistry affected its reinforcing performance. The optimal ball milled sample EM-400 showed 44%, 18%, 9% improved reinforcement in tensile strength, 300% modulus and tear strength of vulcanizates compared with the unmilled PRH. This work provides a facile approach to produce high-performance bio-fillers for rubber industry.