Changes in chemical composition, crystallinity, and microstructure of wood fiber mat-reinforced composite caused by white-rot fungus Trametes versicolor and brown-rot fungus Gloeophyllum trabeum

ABSTRACT Wood fiber mat-reinforced composite (WFMRC) is a novel type of engineering wood-based polymer composite for decorative and building applications. Fungal decay strongly influences the service life of wood composites in outdoor environments. In this study, fungal durability tests were conducted to investigate how white- and brown-rot fungi (Trametes versicolor and Gloeophyllum trabeum, respectively) affect the chemical composition, crystallinity, and morphology of WFMRCs made from two different wood species (poplar and larch). The poplar WFMRC lost more mass (18.3% and 18.4% by T. versicolor and G. trabeum, respectively) than the decayed larch WFMRC (11.4% and 18.4% by T. versicolor and G. trabeum, respectively) after 12 weeks of fungal exposure. Chemical analysis and Fourier-transform infrared spectroscopy measurement revealed the degradation of holocellulose of the WFMRCs after fungal decay. X-ray diffraction analyses demonstrated that fungal decay increased the crystallinity of the poplar WFMRC but decreased the crystallinity of the larch WFMRC. Bore hole formation on the walls of wood cells, cell wall thinning, and collapsed cells were found in decayed samples, particularly in the poplar WFMRC. Although the WFMRCs could be classified as resistant to fungal decay, an appropriate protective measure should be considered to improve the outdoor durability of the WFMRC.