Mechanical characterization of bio-composites fabricated from natural coconut fibre and linear low density polyethylene

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Fibre reinforced composite materials constitute an important class of engineering materials with outstanding mechanical properties, unique flexibility in design capabilities and ease of fabrication. Today, green, environmentally friendly, sustainable, renewable and biodegradable composites from natural fibres are among the most keenly required materials of choice. Coconut fibres can be used as environmentally friendly alternatives to conventional reinforcing fibres in composites. Composites consisting of linear low-density polyethylene (LLDPE) and coconut fibres with percent fibre loading of 10, 20, 30, 40 and 50 respectively were fabricated by extrusion. The extruded strands were pelletized, ground and test samples were injection moulded. The mechanical properties of composites were evaluated using standard American Society of Testing Methods (ASTM). Also, Fourier Transform Infrared Spectroscopy (FTIR) and Swelling Index studies were performed. Coconut fibre (CCF) was treated with sodium hydroxide (NaOH) (5% w/v) for 24 hours. The FTIR results revealed a partial removal of lignin and hemicellulose after the CCF treatment, manifested through the disappearance of the peak at 1740 cm-1. The NaOH treatment increased the tensile strength and tensile modulus in the treated coconut fibre composites (TCFC) whilst slightly decreased the % elongation when compared to the untreated coconut fibre composites (UCFC) at similar % fibre loading, although both were lower than the pure LLDPE. For both the UCFC and TCFC, maximum or optimum ultimate tensile strength was attained at 30% fibre loading (w/w). Generally, the results showed that increasing percent coconut fibre content loading decreased the tensile strength and elongation at break but increased the young’s modulus at similar fibre loading in all cases studied. The swelling index generally increases with increasing amount of fibre loading in the composites with a corresponding decrease in crosslink density.
A thesis submitted to the Department of Chemistry, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfillment of the requirements for the degree of Master of Philosophy (Polymer Science and Technology).