Optimized rice husk biochar as a sustainable reinforcement in emulsion-grade styrene–butadiene rubber composites

Rice husk (RH) poses challenges as a filler in rubber due to self-association and reduced effectiveness from –OH group re-agglomeration, often complicating polymer composite fabrication and thereby deteriorating the final properties of the composite. This study addresses these drawbacks by pyrolyzing RH into biochar under optimized conditions. Optimal filler properties for rubber were observed in biochar samples, with 850 °C RH (biochar derived from rice husk heated to 850 °C) exhibiting the most promising characteristics. Emulsion-grade styrene–butadiene rubber (E-SBR) composites containing 850 °C RH demonstrated significantly improved reinforcement, particularly at a dosage of 20 parts per hundred rubber (phr). This article provides a thorough exploration—from the initial preparation of RH-derived biochar under optimized conditions to the evaluation of its effectiveness as a reinforcing filler in rubber composites, thereby elucidating the structure–property-processing relationships of these novel composites for commercial rubber compounding applications, along with offering a sustainable and high-performance alternative derived from biomass.

This study explores biochar made from rice husks as a sustainable solution for manufacturing E-SBR composites, focusing on selecting, characterizing and applying biochar effectively.