Dynamic Sorption and Hygroexpansion of Wood Subjected to Cyclic Relative Humidity Changes
Keywords:Cyclical relative humidity, dynamic sorption, hygroexpansion, moisture gradient distribution, nonequilibrium state
AbstractTo investigate the behavior of sorption and hygroexpansion of wood at nonequilibrium, Sitka spruce (Picea sitchensis Carr.), 4-mm along the grain and 20-mm in radial and tangential directions, was exposed to sinusoidally RH between 45-75% at 20°C for 1, 6, and 24 h. Moisture changes and radial and tangential dimensional changes measured during the cycling gave the following results: moisture and dimensional changes of the specimens were generally sinusoidal but lagged behind the imposed RH. The phase lag decreased and amplitude increased with increasing cyclic periods. Furthermore, a mathematical model proposed in a previous study was modified to describe the dynamic sorption of wood exposed to cyclical RH. The model not only produced kinetics in good agreement with experiment results, but also can provide moisture gradient distributions developed throughout the wood during cyclical processes.
Bramhall G (1979) Mathematical model for lumber drying, Part 1: Principles involved. Wood Sci 12(1):14-21.nChomcharn A, Skaar C (1983) Dynamic sorption and hygroexpansion of wood wafers exposed to sinusoidally varying humidity. Wood Sci Technol 17(4):259-277.nDroin-Josserand A, Taverdet JL, Vergnaud JM (1988) Modelling the absorption and desorption of moisture by wood in an atmosphere of constant and programmed relative humidity. Wood Sci Technol 22(4):299-310.nGarcía Esteban L, Gril J, De Palacios De Palacios P, Guindeo Casasús A (2005) Reduction of wood hygroscopicity and associated dimensional response by repeated humidity cycles. Ann Sci 62(3):275-284.nHarris JM (1961) The dimensional stability, shrinkage intersection point and related properties of New Zealand timbers. Tech. Paper 36.nJönsson J (2004) Internal stresses in the cross-grain direction in glulam induced by climate variations. Holzforschung 58(2):154-159.nLu JP, Leicester RH (1997) Mechano-sorptive effects on timber creep. Wood Sci Technol 31(5):331-337.nMa EN, Nakao T, Zhao GJ (2009) Adsorption rate of wood during moisture sorption processes. Wood Res-Slovakia 54(3):13-22.nMa EN, Zhao GJ (2006) Hygroexpansion of wood: From equilibrious state to non-equilibrious state. Journal of Beijing Forestry University 28(5):133-138 [in Chinese with summary in English].nMa EN, Zhao GJ, Cao JZ (2005) Hygroexpansion of wood during moisture adsorption and desorption processes. For Studies China 7(2):43-46.nMacromolecule Academy (1958) Physical properties ofmacromolecule. Kyoritsu Press, Tokyo. 386 pp [in Japanese].nNakao T (2002) Theoretical analysis of structural lumber drying schedules. Mokuzai Gakkaishi 48(4):241-248 [in Japanese with summary in English].nSkaar C (1988) Wood-water relations. Springer-Verlag, Berlin, Germany. 283 pp.nStevens WC (1963) The transverse shrinkage of wood. Forest Prod J 13(9):386-389.nTime B (2002) Studies on hygroscopic moisture transport in Norway spruce, Part 1: Sorption measurements of spruce exposed to cyclic step changes in relative humidity. Holz Roh Werkst 60(6):271-276.nWu QL, Ren YK (2000) Characterization of sorption behaviour of oriented strandboard under long-term cyclic humidity exposure condition. Wood Fiber Sci 32(4):404-418.n
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.