Sustainable bio‐reinforcing mangosteen peel biochar filler in styrene‐butadiene rubber: Analysis of thermal, physical, mechanical, and dielectric properties

Abstract Mangosteen peel, an abundant agricultural waste from Chanthaburi, Thailand, was converted into biochar using a traditional furnace, offering a sustainable solution for waste valorization. This biochar was utilized as a bio‐reinforcing filler in styrene‐butadiene rubber (SBR) at 0, 10, 20, 30, and 40 parts per hundred rubber (phr). The biochar was characterized for particle size, morphology, chemical composition, and surface area. Its effects on the mechanical, thermal, physical, and electrical properties of SBR composites were examined. Increasing biochar content significantly enhanced mechanical properties. At 40 phr, tensile strength increased by 75%, modulus at 100% elongation by 42%, strain at break by 72%, and hardness by 21% compared to unfilled rubber, while tear strength improved by 75% due to uniform dispersion in the rubber matrix. Additionally, biochar at 40 phr reduced the swelling index by 11%, scorch time by 41%, and cure time by 38%, improving processing efficiency and durability. Remarkably, the dielectric constant reached 10.17 at 20 Hz (129% increase), demonstrating the potential for applications requiring enhanced electrical properties. This study highlights mangosteen peel biochar as a sustainable filler, combining environmental benefits with improved performance for eco‐friendly rubber composites. Highlights Mangosteen peel was successfully converted into biochar with 86.39% carbon content. Biochar was uniformly dispersed in SBR composites. Tensile and tear strength increased by up to 75% with biochar reinforcement. Swelling index, scorch time, and cure time decreased with biochar addition. At 40 phr, the dielectric constant increased by 129%.