Effects of wood species on durability and chemical changes of fungal decayed wood plastic composites

Moisture sorption and decay resistance of HDPE based wood plastic composites (WPC) made from poplar, Douglas-fir, black locust, white oak, and ponderosa pine were investigated. Dimensional stability of WPC made from poplar was poor while black locust performed extremely well. There were no significant gravimetric differences in composites produced using Douglas-fir, poplar, or pine exposed to Gloeophyllum trabeum (brown rot). However, Trametes versicolor (white rot) produced significantly higher weight losses on HDPE/poplar composites, while Douglas-fir based WPC were less susceptible to this fungus. FTIR spectroscopy showed that white rot selectively decomposed lignin while brown rot degraded both polysaccharides and lignin. Cellulose and hemicelluloses content decreased in WPC exposed to brown rot. Chitin in the fungi cell walls increase polysaccharide content of decayed WPC. The results suggest that poplar and pine would be the preferred wood species for WPC production for applications where conditions would not be suitable for white rot.