Sorption of Moisture by Wood Within A Limited Range of Relative Humidities

Authors

  • Perry N. Peralta

Keywords:

Sorption, adsorption, desorption, isotherm, hysteresis

Abstract

Information on wood sorption behavior provides desorption and adsorption curves from the green and fully dry initial conditions, respectively. Wood in service, however, is exposed to only a narrow range of relative humidities (RH) and, therefore, should exhibit intermediate isotherms that are different from those of the full isotherms. This paper presents the results of a study performed to establish the intermediate desorption curves at 30 C for yellow poplar wood samples subjected to RH ranges of 92% to 0%, 75% to 0%, 53% to 0%, and 32% to 0%. The desiccator method was used to establish the full desorption curve, while a high-vacuum system was employed to obtain the full adsorption and the four intermediate desorption curves. The desired relative humidities were maintained by saturated salt solutions.

The generated intermediate desorption curves all fall within the full adsorption and desorption isotherms, with the isotherms originating from 92%, 75%, 53%, and 32% RH tracing progressively lower curves. These isotherms exhibit relatively short crossovers; a 40% RH change being needed for an intermediate desorption curve to cross over from the full adsorption isotherm to the full desorption isotherm. The intermediate curve from 92% RH has the characteristic sigmoidal shape, but those from 75%, 53%, and 32% RH are concave towards the X-axis. All the intermediate curves exhibit hysteresis, even at low RH levels and narrow RH ranges.

References

Avramidis. S. 1986. Nonisothermal diffusion of moisture in wood and sorption studies. Ph.D. thesis, SUNY College of Environmental Science and Forestry, Syracuse, NY.nJury, W. A., W. R. Gardner, and W. H. Gardner. 1991. Soil physics, 5th ed. John Wiley, New York, NY. 328 pp.nLabuza, T. P. 1984. Moisture sorption: Practical aspects of isotherm measurement and use. American Association of Cereal Chemists, St. Paul, MN. 150 pp.nMorton, W. E., and J. W. S. Hearle. 1975. Physical properties of textile fibers, 2nd ed. John Wiley. New York. NY. 660 pp.nOkoh, K. I. A. 1976. Moisture sorption and electrical resistivity of some woods and barks. Ph.D. thesis, SUNY College of Environmental Science and Forestry. Syracuse. NY.nOkoh, K. I. A. and C. Skaar. 1980. Moisture sorption isotherms of the wood and inner bark of 10 southern US hardwoods. Wood Fiber 12(1):98-111.nPeralta, P. N. 1990. Nonisothermal moisture transport in wood. Ph.D. dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA.nSAS. 1990. SAS/STAT User's guide, Version 6, 4th ed., vol. 2. SAS Institute, Inc., Cary, NC.nSimpson, W. T. 1980. Sorption theories applied to wood. Wood Fiber 12(3):183-195.nSpalt. H. A. 1958. The fundamentals of water vapor sorption by wood. Forest Prod. J. 8:288-295.nSpeakman, J. B., and C. A. Cooper. 1936. The adsorption of water by wool. I. Adsorption hysteresis. J. Textile Inst. 27:T183-T185.nUrquhart, A. R. 1960. Sorption isotherms. Pages 14-32 in J. W. S. Hearle and R. H. Peters, eds. Moisture in textiles. Wiley Interscience, New York, NY.n

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Published

2007-06-25

Issue

Number 1 / January 1995

Section

Research Contributions

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