The Dielectric Properties of Wood VI : On the Dielectric Properties of the Chemical Constituents of Wood and the Dielectric Anisotropy of Wood

Abstract

In this paper, the dielectric properties of the chemical constituents of wood were measured over a wide temperature and frequency ranges in order to elucidate the dielectric anisotropy of wood. In the case of cellulose and mannan the only one temperature dispersion was observed. The dispersion would be due to the rotational motions of methylol groups in the amorphous regions since the dispersion did not occur in xylan. On the other hand, the two dispersions were observed in lignin. The dispersion in high temperature range would be due to the motions of carbonyl groups to which water molecules are attached by hydrogen bonds, while the one in low temperature range would be due to the motions of methylol groups. The temperatures corresponding to the maximum dielectric loss factor for wood in the longitudinal direction coincided with that of cellulose and they were in higher range than those for wood in the transverse directions. These facts, therefore, show that the dielectric relaxation processes of wood in the longitudinal direction are governed by those of cellulose, while the relaxation processes of wood in the transverse directions are considerably influenced by those of lignin.