To evaluate the effect of fungal decay on the physico-mechanical properties of natural composites, a commercial extruded bagasse/polypropylene composite from a manufacturer was sampled. Weight loss, long-term water absorption, flexural modulus, flexural strength, and unnotched impact strength were determined after incubation with white and brown rot fungi for 14 weeks. Results indicated higher water absorption for all incubated samples. However, the water absorption capacity of brown-rotted samples was significantly higher than that of white rotted ones. The brown rot fungus caused more weight loss than the white rot fungus. Modulus of rupture and modulus of elasticity declined after incubation with fungi. The brown rot fungus generally caused a greater reduction in flexural strength than did the white rot fungus. Fungal decay had no significant influence on unnotched impact strength.

Walnut (Juglans regia L.) heartwood extractives were identified and their potential for protection of poplar wood was evaluated. Test specimens were prepared from poplar wood (Populus nigra L.) to meet BS 838:1961 requirements. Samples were impregnated with heartwood extractive solution (1.5, 2.5, and 3.5% w/w in ethanol-toluene), followed by 5 hours vacuum desiccator technique to reach complete saturation. Impregnated specimens were exposed to white-rot fungus (Trametes versicolor) for 14 weeks according to BS 838:1961 applying the kolle-flask method. The weight loss of samples was determined after exposure to white-rot fungus. The highest weight loss (36.96%) was observed for untreated control samples and the lowest weight loss (30.40%) was measured in samples treated with 1.5% extractives solution. The analyses of the extracts using GC/MS indicated that major constituents are benzoic acid,3,4,5-tri(hydroxyl) and gallic acid (44.57 %). The two toxic components in the heartwood are juglone (5.15 %) and 2,7-dimethylphenantheren (5.81 %).

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Variations in average tracheid dimensions (such as length, diameter, lumen diameter, and wall thickness) and its biometrical ratios including slenderness ratio, flexibility ratio, and Runkell ratio, oven-dry and basic density, longitudinal, radial, tangential, and volume shrinkage, maximum moisture content, and porosity of cypress trees wood (Cupressus sempervirens L.var. horizontalis), which was cultivated in the north of Iran, were studied from the pith to bark (radial position), and along the stem from the base upwards. To measure the mentioned traits, the test specimens were prepared from three stands and 9 discs at different height levels (5, 25, and 50% of the total tree height) based on ASTM-D143 standard. Results indicated that the tracheid length, tracheid cross-sectional dimensions, and its biometrical ratios irregularly varied at each height level, along the stem from the bottom to top, but within the discs, at the same height level biometrical traits in the radial position regularly increased from the pith to bark. Within the tree, wood oven-dry and basic density, longitudinal, radial, tangential, and volume shrinkage varied at each height level, decreasing along the stem from the base upwards. Within the discs, at the same height level, wood density and shrinkage, except for longitudinal shrinkage in the radial position, increased from the pith to bark. The maximum moisture content and porosity varied at each height level, increasing along the stem from the bottom to the top of the tree. Moreover, within the discs, at the same height level in the radial direction porosity decreased and maximum moisture content increased except for at 5% of height level from the pith to bark.

This study was performed to determine the effect of boric acid treatment upon the decay resistance and mechanical properties of poplar wood. Test specimens were prepared from poplar wood (Populus nigra L.) to meet ASTM D 143-94 and BS 838:1961 requirements. Samples were impregnated with boric acid solution (0.5, 1, and 2% w/w in distilled water) and by a long-term (21 days) dipping technique to reach complete saturation. Impregnated specimens were exposed to rainbow white-rot fungus (Trametes versicolor) for 14 weeks according to BS 838:1961 as applied by the kolle-flask method. The weight loss, compression strength parallel to the grain, and Brinell hardness were determined after impregnation and exposure to white-rot fungus. The highest weight loss (28.60%) was observed for untreated control samples and the lowest (0.63%) occurred in samples treated with 2% boric acid solution. The highest compression strength parallel to the grain was noted in samples treated with 0.5% boric acid and decayed (22.59 MPa) and the lowest compression strength parallel to the grain was recorded in untreated decayed samples (10.42 MPa). The highest Brinell hardness on tangential surface was observed in samples treated with 1% boric acid and decayed (1.32 KN) and the lowest was noted in untreated decayed samples (0.39 KN). The highest Brinell hardness on radial surface was observed in samples treated with 1% boric acid and decayed (1.07 KN) and the lowest was found in untreated decayed samples (0.35 KN).