Effect of alkali treatment and coupling agent on thermal and mechanical properties of Opuntia ficus-indica cladodes fibers reinforced HDPE composites

In this work, Opuntia ficus-indica ( OFI) fibers were used as natural reinforcement to high-density polyethylene (HDPE) matrix to valorize unexploited Moroccan natural resources in composites applications. Composites specimens were prepared by combining extruder and injection molding processes using various fibers loadings (2.5, 5 and 10 wt%). OFI fibers were alkali treated to clean their surfaces from non-cellulosic compounds, and styrene–(ethylene–butene)–styrene three-block copolymer grafted with maleic anhydride (SEBS-g-MA) is used as coupling agent to graft maleic groups in the surface of matrix. Combined effects of both treatments on thermal and mechanical properties of prepared composites were investigated. Results showed that the alkali treatment proves to be more effective in improving interfacial adhesion between fibers and matrix, which positively influences the hardness and Young’s modulus properties of composites without SEBS-g-MA, while the addition of coupling agent increased composites plasticity and thermal stability owing to the chemical bond formation at fibers–matrix interface.