Tensile and Flexural Properties of Kenaf Fibre-Reinforced Polylactic Acid Composites for Eco-Friendly Product Design

Growing environmental consciousness and regulatory pressure are driving demand for fully compostable natural fibre-reinforced biopolymer composites as alternatives to conventional synthetic materials. This study investigates the tensile and flexural properties of kenaf fibre-reinforced polylactic acid composites, assessing their suitability for eco-friendly consumer product applications in the Nigerian market. Kenaf fibres were sourced from agricultural residues in Borno State, North East Nigeria, treated with alkali and silane, and compounded with polylactic acid at fibre contents of 10, 20, and 30 percent by weight using a twin-screw extruder. Composite specimens were injection-moulded and evaluated following ASTM D638 and D790 procedures. Dynamic mechanical analysis assessed viscoelastic behaviour across a temperature range relevant to product use conditions. Results demonstrate that 20 percent kenaf fibre loading with combined alkali and silane surface treatment produced optimal tensile strength of 57.4 MPa and flexural modulus of 5.8 GPa. Dynamic mechanical analysis confirmed increased storage modulus with fibre addition, indicating stiffening of the biopolymer matrix. Glass transition temperature increased marginally from 62 to 67 degrees Celsius with kenaf addition, suggesting partial restriction of polymer chain mobility. Scanning electron microscopy showed improved interfacial bonding for dual-treated fibres relative to untreated controls. The study concludes that kenaf/polylactic acid composites are technically suitable for rigid consumer product components requiring moderate structural performance and environmental end-of-life advantages. Recommendations include process scale-up trials and lifecycle assessment for full environmental benefit quantification. Keywords: kenaf fibre, polylactic acid, biocomposite, tensile properties, eco-friendly