Utilisation of particles of coconut shell and cow bone as reinforcing materials for the production of low density hybrid polyethylene matrix composites by stir casting method was carried out. 50 µm coconut shell and 50 µm cow bone particulates in different proportions (5 – 25 wt. %) were mixed with polyethylene and the microstructural, physical and mechanical characterisations were determined using standardised methods. The hybrid composite exhibited desirable properties in terms of water absorption (0.3 %) indicating reduced pores/voids. It also exhibited ultimate tensile strength (1.78 MPa) and hardness (12.78 HBN) at 15 wt. % filler addition. The uniform dispersion of the reinforcing particles as observed in the SEM microstructure and the strong adhesion of the particles and polyethylene matrix contributed to the enhancement of the tensile strength and hardness of the composites. Increasing the filler concentration beyond 15 wt. % caused a decrease in the average inter-particle distance/spacing thereby increasing the amount of interparticle stress concentration overlap. This led to higher levels of debonding when tensile stress was applied. This ultimately impaired the tensile strength of the composites. The strain energy stored in the matrix which could be equal to the adhesion/bonding of the particles and polyethylene matrix caused the particle-matrix interface to debond and reduced or impaired the modulus of elasticity of the composites. Generally, the hybrid composites were better than the mono-reinforced composites and unreinforced polyethylene thus showing the efficacy of added particulates. Hence, the development of this biocomposites will reduce environmental pollution and also has the potential for application in areas where low strength composites are required.

Polyethylene composites --- Coconut shell --- Cow bone --- Stir casting --- Characterisation