Barrier properties of <i>Prosopis juliflora</i> branches biomass derived biocarbon and waste <i>Cyperuspangorei</i> microfibre reinforced vinyl ester composite

This study aims to develop sustainable vinyl ester composites reinforced with waste Cyperus pangorei microfibers and biocarbon derived from Prosopis juliflora biomass, and to evaluate their mechanical, dielectric, and thermal performance. The composites were fabricated using a stir-casting technique, with biocarbon produced via pyrolysis at 800°C serving as a functional carbonaceous filler and microfibers providing structural reinforcement. Among the developed composites, VWB2 (3 vol.% biocarbon and 30 vol.% microfibers) exhibited the best balance of properties, achieving tensile strength of 141 MPa, flexural strength of 162 MPa, hardness of 83 (Shore D), impact strength of 6.9 J, and a dielectric permittivity of 6.1 at 8 GHz, attributed to uniform filler dispersion and improved stress transfer and interfacial polarization. In contrast, VWB3 (5 vol.% biocarbon) showed superior thermal performance, with thermal conductivity of 0.38 W/mK and enhanced thermal stability (88% weight retention at 342°C and a DTG peak at 351°C), due to the formation of efficient heat conduction pathways and protective char structures. SEM analysis confirmed the correlation between filler dispersion and composite performance. These results demonstrate that waste-derived biocarbon and natural microfibers can effectively enhance multifunctional properties of vinyl ester composites, making them suitable for lightweight structural, automotive, electromagnetic shielding, electrical insulation, and thermal management applications. The study provides a sustainable strategy for converting invasive and agricultural biomass wastes into high-performance polymer composite materials.