Changes of dielectric relaxation of wood by acetylation

The longitudinal dielectric constant and dielectric loss of oven-dried acetylated hinoki (Chamaecyparis obtusa) wood samples with different percentages of weight gain (WPG) were measured in the temperature range from -150 degreesC to 0 degreesC and in the frequency range from 1 kHz to 1 MHz. By applying a sech law to results of the dielectric loss, relaxation spectra due to the relaxation of methylol groups were calculated. The distribution of relaxation times became broader with increasing WPG and with decreasing temperature, but the relaxation magnitude for sample with different WPG levels was constant irrespective of temperature. As compared with the average relaxation time and the apparent activation energy of the untreated sample, these values decreased slightly in the samples with WPG of 5.4% and 9.7% and increased in the sample with a WPG of 22. 5%. The numbers of methylol groups involved in a unit volume of cell wall for the samples with WPG of 5.4%, 9.7% and 22.5% were 0.83, 0.71 and 0.43 times that of the untreated sample, respectively.