Sustainable surface modification of sorghum residue-based fiber reinforced polymer composites: Properties and adhesion mechanism

•Hybrid treated fibers obtained from sorghum stalk dispersed well within the rLDPE matrix thereby producing a more homogenous composite material.•Thermo-alkali and thermo-laccase fibre modification treatments were employed to improve the properties of the composites.•The degradation temperature of the treated composites increased with treatment duration due to the improved removal of waxes and oils, and increased surface roughness leading to increased fiber/matrix adhesion.•Hybrid thermo-alkali treatment was better, in comparison to thermo-laccase treatment, at eliminating undesired contaminants in the fibers.•The thermo-alkali reinforced composite, which was treated for 10 days, be utilized for non-structural applications such as wall and floor paneling in buildings.