Abstract:

To determine the states of water and its fraction in frozen tree in winter, the heating and cooling curves of Populus ussuriensis and Pinus koraiensis green timber specimens were tested and analyzed respectively using differential scanning calorimetry(DSC 204). The positions of exothermic and endothermic peaks, which were shown on the DSC curves, caused by freezing and melting of water in wood were located, and the areas of endothermic peaks were measured by using an integration method, then the states of water and its fraction in frozen wood were evaluated. The results showed that:1) It was feasible to determine the states of water and its fraction in frozen wood using DSC. The DSC curves illustrate that there were three types water in green wood:frozen free water, frozen bound water and nonfrozen water. 2) The positions of exothermic peak induced by freezing of free water in Pinus koraiensis and Populus ussuriensis specimens were about -13 ℃ and -18 ℃ as temperature decreased; the positions of endothermic peak induced by melting of bound water and free water were about -0.4 ℃, 6 ℃ and 0.8 ℃, 9 ℃ respectively as temperature increased. 3) Considering latewood and earlywood of sapwood and heartwood, the ratios of frozen water contents to moisture content were 80.3%, 75.8%, 75.2% and 77.3% in Pinus koraiensis, 69.4%, 68.5%, 63.3% and 89.0% in Populus ussuriensis when temperature was -60 ℃.

Key words: frozen wood, free water, bound water, differential scanning calorimetry (DSC)