Compression behaviors of acetylated wood in organic liquids. Part I. Compression in equilibrium conditions

The radial compression behaviors of acetylated cedar wood were measured in various liquids. The compressive Young’s modulus (E) of acetylated wood was reduced by soaking in water, toluene, and acetone, but it was always greater than that of water-swollen unmodified wood at the same swelling level. The behaviors of acetone-swollen unmodified wood were similar to those of acetylated wood rather than those of water-swollen unmodified wood. These results indicated that the swelling of hydrophobic wood components had a lesser influence on the E of wood than the water-swelling of unmodified hydrophilic components. After large compression (ε > 45%), a part of the strain remained unrecovered because of irreversible mechanical deformation. Since the remaining strain was smaller in the wood specimens indicating greater stress relaxation, it was assumed that the viscoelastic deformation of amorphous matrix components is important for lesser irreversible deformation and effective shape recovery of wood. In contrast with water-swollen unmodified wood, the acetylated wood and acetone-swollen unmodified wood exhibited greater shape recovery despite their relatively higher E. This suggested that the swelling of hydrophobic wood components reduced the viscosity of the matrix rather than its elasticity, resulting in more effective shape recovery with lesser softening.