BIODETERIORATION OF PRODUCTS MADE FROM AUSTRALIAN CEDAR (Toona ciliata M. Roem. var. australis)

Abstract

The objectives of this study were to evaluate the natural resistance of composite and solid wood panels from Toona

ciliata to fungal attack through accelerated laboratory testing, to characterize the anatomical components of the wood according to IAWA, to quantify the soluble and insoluble lignin contents by acid hydrolysis and to determine the colorimetric parameters before and after fungal attack by using the CIE-L*a*b*(1976) system. Solid wood was classifi ed as moderately and highly resistant to white-rot fungus (Trametes versicolor) and to brown-rot fungus (Gloeophyllum trabeum). OSB panels were found to be resistant and moderately resistant to white-rot fungus and highly resistant to brown-rot fungus. Variation in species and particle type did not have a positive effect on the treatments. As regards the wood, both fungi were inhibited by the presence of phenolic resin. Particleboard panels were classifi ed as moderately resistant to white-rot fungus. Treatments T2 (cedar) and T4 (cedar-eucalyptus) were resistant while treatment T3 (cedar-pine) was not resistant to attack by brown-rot fungus. The urea-formaldehyde resin failed to inhibit attack in the same way the phenolic resin did. Anatomically, the species was found to have medium texture, straight vessel lines, pleasant smell after incision and poor luster on the radial surface. Its anatomical structure favored colonization by the threadlike fi laments of the fungi. All treatments caused wood darkening after attack by the G. trabeum fungus, with total variation in color. It was observed that with weight loss an increase followed in insoluble lignin contents, in all treatments, indicating that this chemical property is a

determining factor in wood resistance to the attack of the fungi being evaluated.