Effect of antioxidants and fire retardants as mineral fillers on the physical and mechanical properties of high loading hybrid biocomposites reinforced with rice husks and sawdust

In this study, the physical and mechanical properties of recycled high density polyethylene (rHDPE) reinforced with a high loading hybrid of rice husks and sawdust were evaluated, and the effect of antioxidants (AOs) and fire retardants (FRs) as additives were investigated. The rHDPE and natural fibres were compounded into pellets by a compounder, then the pellets were extruded using a counter-rotating twin-screw extruder and test specimens were prepared using the hot and cold press process. Maleic anhydride was used as a coupling agent to increase the adhesion of the fibre/matrix interface. The thermal behaviour of biocomposites was evaluated using a thermal gravimetric analyser (TGA). The mechanical behaviour was measured using tensile, flexural and impact testing in comparison with non-added AOs and FRs. From the study, samples with 0.5 wt.% of antioxidants and 20 wt.% of fire retardants produce the most reasonable strength and elasticity of composites. Furthermore, the effect of the presence of antioxidants and fire retardants on water uptake was minimal. Microstructure analysis of the fractured surfaces of biocomposites confirmed improved interfacial bonding.

► Rice husks and sawdust as hybrid fibre for recycled HDPE base.
► The presence of antioxidants and fire retardants as mineral fillers in biocomposites.
► Mechanical and physical properties of biocomposites.
► Interfacial adhesion between the fillers and the matrix polymer.