Moisture Dependent Softening Behavior of Wood
Keywords:
Viscoelastic behavior, wood, thermal softening, high-temperature, glass transitionAbstract
An improved understanding of material behavior during the manufacture of wood-based composites can increase the efficiency of wood utilization and provide insight into the development of new processes and products that manipulate the viscoelastic nature of wood. One specific area where additional knowledge can be of great benefit is the influence of heat and moisture on the softening behavior of wood.
The thermal softening behavior of wood at four moisture levels from 0 to 20% was evaluated using dielectric thermal analysis (DETA). Coincident in situ relaxations attributed to the softening of amorphous wood components in the range of 20 to 200°C were observed and found to exhibit the characteristics of a glass transition. The moisture dependence of this transition was characterized, and differences in the observed Tg were detected between juvenile and mature wood. Time-temperature superposition was also shown to be applicable to the wood and water system.
References
Aklonis, J. J., and W. J. MacNight. 1983. Introduction to polymer viscoelasticity. John Wiley and Sons, New York, NY.nArmstrong, J. P., C. Skaar, and C. deZeeuw. 1984. The effect of specific gravity on several mechanical properties of some world woods. Wood Sci. Technol. 18:137-146.nAtack, D. 1981. Dynamic mechanical loss properties of wood. Philos. Mag. A. 43(3):619-625.nBack, E. L., and N. L. Salmen. 1982. Glass transitions of wood components hold implications for molding and pulping processes. Tappi 65(7):107-110.nBecker, H., and D. Noack. 1968. Studies on the dynamic torsional viscoelasticity of wood. Wood Sci. Technol. 2:213-230.nCasey, L. J. 1987. Changes in wood-flake properties in relation to heat, moisture and pressure during flakeboard manufacture. M.S. thesis, V.P.I. & S.U., Blacksburg, VA.nChow, S. Z., and K. J. Pickles. 1971. Thermal softening of wood and bark. Wood Fiber 3:166-178.nConnolly, M., and B. Tobias. 1992. Thermoset cure by dynamic mechanical, dielectric and calorimetric methods. Amer. Lab. 24(1):38-42.nCousins, W. J. 1976. Elastic modulus of hemicellulose as related to moisture content. Wood Sci. Technol. 10:9-17.nCousins, W. J. 1978. Young's modulus of hemicellulose as related to moisture content. Wood Sci. Technol. 12:161-167.nCowie, J. M. G. 1991. Polymers: Chemistry and physics of modern materials, 2nd ed. Blackie Academic and Professional, New York, NY.nEaton, R. F., T. H. Tran, M. Shen, T. F. Schatzki, and E. Menefee. 1976. Water dependent beta relaxations in cellulose and its derivatives. Polymer Prepr. 17(2):54-58.nFerry, J. D. 1980. Viscoelastic properties of polymers, 3rd ed. John Wiley and Sons, New York, NY.nFunakoshi, H., N. Shiraishi, M. Norimoto, T. Akoi, H. Hayashi, and T. Yokota. 1979. Studies on the thermoplasticization of wood. Holzforshung 33(5):159-166.nGoring, D. A. I. 1963. Thermal softening of lignin, hemicellulose and cellulose. Pulp Paper Mag. Can. 64(12):517-527.nHedvig, P. 1977. Dielectric spectroscopy of polymers. John Wiley and Sons, New York, NY.nHillis, W. E., and A. N. Rosa. 1978. The softening temperatures of wood. Holzforshung 32(2):68-73.nHöglund, H., U. Sohlin, and G. Tistad. 1976. Physical properties of wood in relation to chip refining. Tappi 59(6):144-147.nIrvine, G. M. 1984. The glass transitions of lignin and hemicellulose and their measurement by differential thermal analysis. Tappi 67(5):118-121.nKelley, S. S., T. G. Rials, and W. G. Glasser. 1987. Relaxation behavior of the amorphous components of wood. J. Mater. Sci. 22:617-624.nKretschmann, D. E., and B. A. Bendsten. 1992. Ultimate tensile stress and modulus of elasticity of fast-grown plantation loblolly pine lumber. Wood Fiber Sci. 24(2):189-203.nLenth, C. A., and F. A. Kamke. 2001. Equilibrium moisture content of wood in high temperature pressurized environments. Wood Fiber Sci. 33(1):104-118.nMcCrum, N. G., B. E. Read, and G. Williams. 1967. Anelastic and dielectric effects in polymeric solids. John Wiley and Sons, New York, NY.nMizumachi, H. 1991. Wood-polymer composites, in Wood and cellulosic chemistry. Marshall Dekker, New York, NY.nNeter, J., and W. Wasserman. 1974. Applied linear statistical models. Richard D. Irwin Inc., Homewood, IL.nÖstberg, G., L. Salmen, and J. Terlecki. 1990. Softening temperature of moist wood by differential scanning calorimetry. Holzforshung 44(3):223-225.nRials, T. J. 1992. Cure analysis of phenol-formaldehyde resins by microdielectric spectroscopy, in W. G. Glasser and H. Hatakeyama, eds. Viscoelasticity of biomaterials. ACS Symposium Series 489 18:282. ACS, Washington D.C.nSadoh, T. 1981. Viscoelastic properties of wood in swelling systems. Wood Sci. Technol. 15:57-66.nSalmen, L., and E. L. Back. 1977. The influence of water on the glass transition of cellulose. Tappi 60(12):137-140.nSalmen, N. L. 1984. Viscoelastic properties of in situ lignin under water-saturated conditions. J. Mater. Sci. 19:3090-3096.nShutler, E. L. 1992. Relating the compression and recovery of polymeric cellular materials to the dimensional stability of wood composites. M.S. Thesis, West Virginia University, Morgantown, WV.nTakahashi, K., T. Morooka, and M. Norimoto. 1998. Thermal softening of wet wood in the temperature range of 0 to 200°C. Wood Research 85:78-80.nTorgovnikov, G. I. 1993. Dielectric properties of wood and wood-based materials. Springer-Verlag. Berlin, Germany, 196 pp.nUhmeier, A., T. Morooka, and M. Norimoto. 1998. Influence of thermal softening and degradation on the radial compression behavior of wet spruce. Holzforshung 52(1):77-81.nWard, I. M. 1983. Mechanical properties of solid polymers, 2nd ed. Wiley-Interscience, New York, NY.nWert, C. A., M. Weller, and D. Caulfield. 1984. Dynamic loss properties of wood. J. Appl. Phys. 56(9):2453-2458.nWetton, R. E., M. R. Morton, and A. M. Rowe. 1986. Comparison of information obtained during epoxy cure by DMTA and DETA techniques. Pages 439-440 in Proc. ANTEC 86, Boston, Mass, Apr. 28-May 1, 1986. Technomic Pub., Lancaster, PA.nWolcott, M. P. 1989. Modeling viscoelastic cellular materials for the pressing of wood composites. Ph.D. dissertation, V.P.I. and S.U., Blacksburg, VA.nWolcott, M. P., F. A. Kamke, and D. A. Dillard. 1990. Fundamentals of flakeboard manufacture: Viscoelastic behavior of the wood component. Wood Fiber Sci. 22(4)345-361.nWolcott, M. P., F. A. Kamke, and D. A. Dillard. 1994. Fundamental aspects of wood deformation pertaining to manufacture of wood-based composites. Wood Fiber Sci. 26(4):496-511.nYoung, R. J., and P. A. Lovell. 1991. Introduction to polymers, 2nd ed. Chapman and Hall, London, UK.n
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