The Effect of Cyclic Relative Humidity Changes on Moisture Content and Thickness Swelling Behavior of Oriented Strandboard


  • Laura Moya
  • William T. Y. Tze
  • Jerrold E. Winandy


Fire-impacted wood, oriented strandboard, cyclic humidity exposure, thickness swelling modeling


This study examines the effect of cyclic RH exposure on MC and thickness swelling (TS) of oriented strandboard (OSB) made from fire-impacted trees. Two specimens were cut from the center of each OSB panel and one was edge-sealed. After being conditioned to 65% RH, specimens were placed in a climate-controlled chamber and subjected to three cyclic changes of 90 - 30% RH at 20°C. Experimental data were characterized by three time-dependent MC or TS models: logarithmic, power law, and exponential. The latter two models gave the best fits showing that edge-sealing reduced the extent of swelling during adsorption and reduced the moisture loss at desorption. The models also described the effect of burnt level and bark throughout the humidity exposure cycles. The exponential model revealed no significant effect of burnt level on the panel TS. Both the power law and exponential models indicated that addition of charred bark to the panels significantly decreased the maximum amount of moisture and thickness change. The exponential model revealed an increase in equilibrium TS at the end of each RH cycle compared with the end of precyclic desorption. True nonrecoverable TS was difficult to discern in Cycle 1 because of moisture hysteresis, but the nonrecoverable effect was evident in Cycles 2 and 3.


Dinwoodie JM (1981) Timber: Its nature and behaviour. Van Nostrand Reinhold Co., New York, NY. 190 pp.nEricksson L (1967) Versuchsbericht Kriechen von Spanplatten. 17. Sitzung der Techn. Kommission der FESYP, Brüssel. Cited by Pierce et al (1979).nFan MZ, Bonfield PW, Dinwoodie J, Enjili V (2006) Effect of test piece size on rheological behavior of wood composites. J Eng Mech 132(8):815 - 822.nFan MZ, Dinwoodie JM, Bonfield PW, Bresse MC (2004) Dimensional instability of cemented bonded particle-board. Part 2: Behaviour and its prediction under cyclic changes in RH. Wood Sci Technol 38:53 - 68.nGerhards CC (2000) Bending creep and load duration of Douglas-fir 2 by 4s under constant load for up to 12-plus years. Wood Fiber Sci 32(4):489 - 501.nHoyle RJ Jr., Itani RY, Eckard JJ (1986) Creep of Douglasfir beams due to cyclic humidity fluctuations. Wood Fiber Sci 18(3):468 - 477.nHoyle RJ Jr., Itani RY, Anderson JT (1994) The effect of moisture cycling on creep of small glued laminated beams. Wood Fiber Sci 26(4):556 - 562.nJohnson JW (1964) Effect of exposure cycles on stability of commercial particleboard. Forest Prod J 14(7):277 - 282.nLu JP, Leicester RH (1997) Effect of cyclic humidity exposure on moisture diffusion in wood. Wood Fiber Sci 29(1):68 - 74.nMartensson A (1994) Mechano-sorptive effects in wooden materials. Wood Sci Technol 28:437 - 449.nMoya L, Winandy JE, Tze WTY, Ramaswamy S (2008) Use of fire-impacted trees for oriented strandboards. Forest Prod J 58(6):45 - 52.nMundi JS, Bonfield PW, Dinwoodie JM, Paxton BH (1998) Modelling the creep behavior of chipboard: The rheological approach. Wood Sci Technol 32:261 - 272.nMuszynski L, Lagana R, Shaler SM, Davids W (2005) Comments on the experimental methodology for determination of the hygro-mechanical properties of wood. Holzforschung 59:232 - 239.nMuszynski L, Wang F, Shaler SM (2002) Short-term creep tests on phenol-resorcinol-formaldehyde (PRF) resin undergoing moisture content changes. Wood Fiber Sci 34(4):612 - 624.nNemli G, Hizirouglu S, Usta M, Serin Z, Ozdemir T, Kalaycioglu H (2004) Effect of residue type and tannin content on properties of particleboard manufactured from black locust. Forest Prod J 54(2):36 - 40.nNofal M, Kumaran K (2003) Behavior of engineered wood materials under the effect of wetting and drying cycles. Tech Rep NRCC-43390. NRCC Institute for Research in Construction, Ottawa, Canada. 12 pp.nNuñez AT, Marcovich NE, Aranguren MI (2004) Analysis of the creep behavior of polypropylene-woodflour composites. Polym Eng Sci 44(8):1594 - 1603.nOlsson AM, Salmén L, Eder M, Burgert I (2007) Mechanosorptive creep in wood fibres. Wood Sci Technol 41:59 - 67.nPenneru AP, Jayaraman K, Bhattacharyya D (2006) Viscoelastic behavior of solid wood under compressive loading. Holzforschung 60:294 - 298.nPierce CB, Dinwoodie JM (1977) Creep in chipboard. Part 1. Fitting 3- and 4-element response curves to creep data. J Mater Sci 12:1955 - 1960.nPierce CB, Dinwoodie JM, Paxton BH (1979) Creep in chipboard. Part 2. The use of fitted response curves for comparative and predictive purposes. Wood Sci and Technol 13:265 - 282.nShi SQ, Gardner DJ (2006) Hygroscopic thickness swelling rate of compression molded wood fibreboard and wood fiber/polymer composites. Compos Part A-Appl S 37:1276 - 1285.nShi SQ, Gardner DJ (2007) Diffusion model based on Fick's second law for the moisture absorption process in wood fiber-based composites: Is it suitable or not? Wood Sci Technol 41:645 - 658.nSigmaPlot 8.0 (2002) SigmaPlot 2002 for Windows, Version 8.02. SPSS Inc., Chicago, IL.nStamm AJ (1964) Wood and cellulose science. The Ronald Press Company, New York, NY. 549 pp.nSuchsland O (2004) The swelling and shrinking of wood. A practical technology primer. Forest Prod Soc., Madison, WI. 194 pp.nTime B (2002) Studies on hygroscopic moisture transport in Norway spruce. Part 2: Modelling of transient moisture transport and hysteresis in wood. Holz Roh Werkst 60:405 - 410.nWu Q, Lee JN (2002) Thickness swelling of oriented strandboard under long-term cyclic humidity exposure condition. Wood Fiber Sci 34(1):125 - 139.nWu Q, Milota MR (1995) Rheological behaviour of Douglas-fir perpendicular to the grain at elevated temperatures. Wood Fiber Sci 27(3):285 - 295.n






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