Effect of Heat Treatment of Wood Flour on the Mechanical Properties of Outdoor Weathered Red Balau/LDPE Composites

Abstract

The interest in replacing synthetic fillers with biodegradable natural fillers from renewable resource in thermoplastic composites is gradually gaining attention. This has led to an upsurge in the use of wood flour as fillers in wood thermoplastic composites (WTC). Wood offers the advantages of being renewable, biodegradable, good strength to weight ratio and tribological properties. However, the hydrophilic properties of wood, intrinsically connected with its cell wall polymers confer some limitations in its use in WTC. Therefore, some modification is required. Usually, chemicals are used to modify wood to enhance the properties of WTC. This possesses environmental challenges as effluents are generated and disposal becomes a problem. Thermal treatment is another wood modification method employed to checkmate the limitations of wood. In thermal treatment, wood is subjected to higher temperatures than drying in a controlled environment. This results in the reduction of the OH groups on the surface of the wood polymers, resulting in reduced polarity. This offers a better alternative as an environmentally benign way to modify wood. In this study, Red Balau saw dust was modified by subjecting it to 180˚C and 200˚C in an oven and compounded with LDPE, then moulded in an injection moulding machine. Samples were exposed to outdoor weathering and tested for mechanical properties to assess the effects of heat treatment on the tensile and flexural properties of weathered and unweathered samples. Results revealed that the mechanical properties of untreated weathered samples deteriorated more than the heat treated composites. Reduced hydrophilicity, resulting from wood flour heat treatment which led to better compatibility between the matrix and the fillers, conferred better interfacial adhesion and resulted in the observed trend. Therefore, heat treatment is an environmental friendly way of modifying the chemistry of wood polymers for property enhanced composites