Utilizing Coconut Biochar as a Bio‐reinforcing Agent in Natural Rubber Composites

Abstract This research investigates the pyrolysis of biochar from different parts of residual aromatic young coconut waste, namely coconut fruit, coconut bunch, and coconut leaf, to be used as fillers in natural rubber (NR). Scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy reveals that biochar has a flake‐like structure with a high carbon content (67%–77%). The biochar is mixed with NR using a two‐roll mill at filler contents of 0, 10, 20, 30, and 40 phr (part per hundred of rubber). Adding coconut fruit biochar at 40 phr increases the Shore A hardness to 59.62, a remarkable 47% improvement compared with unfilled NR. The maximum tensile strength occurs at 20 phr, while the highest tensile modulus (4.53 MPa) and tear strength (17,344 N m −1 ) are observed at 40 phr. Moreover, the swelling index of composites in toluene decreases slightly as biochar content increases, and the crosslink density is higher for NR filled with coconut fruit biochar than for other biochar types. Based on these results, coconut fruit biochar is identified as the most effective reinforcement filler for NR among the biochar types studied. Consequently, it can be used as a bio‐reinforcing agent in NR composites, contributing to sustainability and eco‐friendliness.