The effects of residual lignin content on wood fibre reinforced polypropylene composites

This study investigates the effect weathering on composites made from fibre subjected to various stages of a standard Kraft pulping process. Pre-washed, washed and bleached Kraft wood fibre of kappa numbers 27, 17, and I was assessed in terms of its surface potential using the streaming potential method and combined with polypropylene (PP) to produce composites. Composites were prepared using a twin screw extruder followed by pelletising and injection moulding. Tensile testing, hardness testing and impact testing were carried out to evaluate the composite mechanical properties. It was found that fibre with higher amounts of residual lignin content led to composites with lower tensile and impact strengths and increased degradability when subjected to accelerated weathering testing.