Biochar filled high-density polyethylene composites with excellent properties: Towards maximizing the utilization of agricultural wastes

Biochar derived from agricultural wastes was used to reinforce high-density polyethylene (HDPE) to obtain composites abbreviated as B10, B20, B30, B40, B50, B60, and B70. Investigating the mechanical, thermal, water absorption and flame retardant properties of the composites is one of the objectives while maximizing the utilization of agricultural wastes is the ultimate goal of this work. It was found that flexural properties, tensile properties, storage modulus, elasticity, creep resistance and anti-stress relaxation ability of HDPE were improved by the inclusion of biochar, and excellent mechanical properties were obtained in 50 % even 60 % biochar added composites because of good dispersion and unique structure shown in the interface. The composites achieved good flexural strength of 34.95 MPa in B50, flexural modulus of 1.79 GPa in B40, tensile strength of 29.05 MPa in B40, and tensile modulus of 2.03 GPa. Additionally, the thermal and flame retardant properties (limited oxygen index of 25.06 % in B70) increased for the biochar added composites as the biochar loading increased due to the high thermal stability of biochar, although biochar had a negative effect on water-resistance of the composites. The results revealed that the ultimate goal was achieved in terms of producing composites with excellent mechanical, thermal, water absorption and flame retardant properties while maximizing the utilization of agricultural wastes as a rational balance.