Mechanical properties of wood in an unstable state due to temperature changes, and analysis of the relevant mechanism VI: Dielectric relaxation of quenched wood

Abstract

To analyze the effects of lignin on the destabilization of wood due to quenching, we examined the dielectric properties of untreated and delignified wood before and after quenching at 20°C from 50 Hz to 100 MHz. For untreated wood, the inflection points of log ε′ and log σ vs log f and the peak of log(tan δ) vs log f were attributed to interfacial polarization before quenching, and the location of the inflection point shifted to a higher frequency with increasing moisture content because of changes in the water cluster. After quenching, the inflection points of log ε′ and log σ and the peak of log(tan δ) shifted to higher frequency; however, the values of log ε′, log σ recovered to those before quenching with the passage of time. For delignified wood, dielectric relaxation was observed at a higher frequency than for untreated wood irrespective of quenching. It was inferred that the mobility of water molecules was influenced by the cluster surroundings because of increased number of adsorption sites in hemicellulose. Moreover, after quenching, the recovery process did not change greatly over time; it was shown that the matrix structure was affected more by quenching with the loss of lignin. © 2008 The Japan Wood Research Society.