Abstract: In this study,Chinese Fir(Cunninghamia lanceolata) plantation wood was dried by high-temperature drying(HTD),low-temperature drying(LTD) and freezevacuum drying(FVD) methods,and their dynamic viscoelastic properties were tested at various humidity environments.The measurements were done in the temperature range of-120 to 40 ℃ at frequencies ranging between 0.5 to 10 Hz.The results showed that: with the increase of moisture contents,the decrease of storage modulus with increasing temperature became more dramatically.The decrease extent of storage modulus was the lowest for high-temperature dried wood.Two mechanical relaxation processes were observed for three kinds of dried woods.The α relaxation process in higher temperature range was due to glass transition of hemicellulose with low molecular weight,while the β relaxation process occurred in lower temperature range was based on the reorientation of methylol groups in amorphous of wood cell wall and the reorientation of adsorbed water molecule in wood.The loss peak temperature of mechanical relaxation processes moved to lower temperature range with the increase of moisture contents,and moved to higher temperature range with the testing frequency increase.The apparent activation energy of mechanical relaxation processes decreased with the increase of moisture contents.For α relaxation process,high-temperature and low-temperature dried woods showed lower value than that for freeze-vacuum dried wood.

Key words: dried wood, mechanical relaxation process, moisture content, apparent activation energy