The effect of donor-acceptor interactions on the mechanical properties of wood

Abstract

This paper explores the empirical correlations between the mechanical properties of solvent-treated wood and solvent parameters. Wood beams (10 inch x 0.7 inch x 0.4 inch) of lauan, birch, and Douglas fir were soaked in five solvents (benzene, dioxane, methanol, dimethyl sulfoxide, and distilled water) for 4 months at room temperature (23°C) and then mechanically tested in bending. The acoustic emission (AE) energy (related to failure energy), the modulus of rupture (MOR), and the modulus of elasticity (MOE) of the specimens were determined. It was found that all of these properties of the specimens decreased with the solvent strength parameter which was related to acceptor number (AN), donor number (DN) and molecular volume (MV ). The linear correlation of the AE energy of the specimens with the solvent parameter (AN + DN)1/2 was verified. Alternative relationships between the AE energy, MOR or NIOE of the specimens and the modified solvent strength parameters, 2.5 DN + AN or DN/MV1/3, were explored. The microstructures of fracture surfaces of lauan specimens were examined by scanning electron microscopy (SEM) and showed dramatic changes when the solvent strength increased, such as microfibril pull-out and a decrease in roughness of the fracture surfaces of cell walls. All these observations reflected the changes in mechanical properties and the mean AE energy qualities of the specimens.