Influence of moisture content on the vibrational properties of hematoxylin-impregnated wood

The vibrational property of hematoxylin-impregnated wood was investigated from the aspect of moisture content dependence. The specific dynamic Young's modulus (E/gamma) and loss tangent (tan delta) of hematoxylin-impregnated wood were determined in the relative humidity (RH) range of 0%-97%, and were compared with those of the untreated and some conventional chemically treated woods. The changes in the E/gamma and tan delta of wood with increasing RH were suppressed by acetylation and formaldehyde treatment because of a marked reduction in the hygroscopicity of the wood. Although the hematoxylin impregnation did not significantly affect the hygroscopicity of the wood, its influence on E/gamma and tan delta were similar to that of formaldehyde treatment at low RH and of acetylation at medium RH. It was supposed that at low to medium RH hematoxylin restrains the molecular motion of amorphous substances in the cell wall because of its bulkiness and rigidity. On the other hand, at high RH it seems to work as a plasticizer with adsorbed water molecules.