Strategies for improving the resistance of wood-plastic composites (WPC) against wood-decay fungi

In Europe, most commercial wood-plastic composites (WPC) contain 60-70 % (by weight) of wood particles, usually in the form of wood flour, and are therefore potentially susceptible to degradation by wood decay fungi. The amount of susceptibility to fungal decay depends on various factors such as amount of wood, wood species, wood particle geometry, processing (quality wood encapsulation by the thermoplastic polymer) and presence of additives. Wood decay fungi require a certain amount of moisture, therefore, it is of paramount importance to minimize water uptake of the composites to inhibit fungal growth. In this project, two strategies were pursued to minimize fungal decay in the WPC: the use of robinia (Robinia pseudoacacia), a wood species with high natural resistance to decay, and the use of refiner fibres (thermomechanical pulp fibres) as opposed to wood flour. It was assumed that improved interfacial adhesion can be achieved in WPC with refiner fibres due to coating of fibre with lignin during the refining process; this should reduce water uptake and fungal degradation. It was decay fungi to WPC. Robinia refiner fibres show potential for improvement of mechanical properties and reduction of moisture uptake in WPC.