Flakeboard Thickness Swelling. Part I. Stress Relaxation in a Flakeboard Mat
Keywords:
Flakeboard, steam injection, thickness swelling, dimensional stability, springbackAbstract
The steam injection schedule best suited for dimensionally stabilizing a flake mat is one in which steam treatment is initiated before the press is closed and is continued at least until the mat attains target thickness. Experiments showed that resinless mats treated with 20 sec of steam at 600 kPa had maximum thickness swelling of 205% compared to 350% for resinless mats pressed in a conventional fashion. Reductions in thickness swelling were proportional to steam duration and pressure. Mats treated with 20 sec of steam at 1,950 kPa had only one-tenth the thickness swelling measured in conventionally pressed mats. We believe that reduction of thickness swelling is dependent on a number of factors, including plasticization of the wood, "lignin" flow, and molecular changes in the wood structure.References
Dwianto, W., F. Tanaka, M. Inque, and M. Norimoto. 1996. Crystallinity changes of wood by heat or steam treatment. Wood Res. Bull. 83:47-49, Wood Research Institute, Kyoto University, Japan.nGeimer, R. L. 1983. Method of pressing reconstituted lignocellulosic materials. U. S. patent 4393019, July 12.nGeimer, R. L., and J. H. Kwon. 1988. Flakeboard thickness swelling. II. Fundamental response of board properties to steam injection pressing. Wood Fiber Sci. (in press).nGoring, D. A. I. 1963. Thermal softening of lignin, hemi-cellulose and cellulose. Pulp & Paper Mag. Can. 64(12): 517-527.nHeebink, B. G., and F. V. Hefty. 1968. Steam post treatments to reduce thickness swelling of particleboard (exploratory study). Research Note FPL-0187, USDA, Forest Serv., Forest Prod. Lab., Madison, WI. 27 pp.nHsu, W. E., W. Schwald, and J. A. Shields. 1988. Chemical and physical changes required for producing dimensionally stable wood-based composites. Part 1. Steam pretreatment. Wood Sci. Technol. 22(3):281-289.nHsu, W. E., W. Schwald, and J. A. Shields. 1989. Chemical and physical changes required for producing dimensionally stable wood-based composites. Part 2. Heat post-treatment. Wood Sci. Technol. 23(3):281-288.nKamke, F. A., and L. J. Casey. 1988. Fundamentals of flakeboard manufacture: Internal-mat conditions. Forest Prod. J. 38(6):38-44.nOkamoto, H., S. Sano, S. Kawai, T. Okamoto, and H. Sasaki. 1994. Production of dimensionally stable medium density fiberboard by use of high-pressure steam pressure. Mokazai Gakkaishi 40(4):380-389.nPrice, E. W., and R. L. Geimer. 1986. Thick composites are technically feasible with steam-injection pressing. Pages 65-71 in Proc., Composite Board Products for Furniture and Cabinets—Innovations in Manufacture and Utilization. Nov. 11-13, Greensboro, NC. Forest Products Society, Madison, WI, 1989.nRazali, A. K. 1985. Origins of thickness swelling in particleboards. Ph.D. thesis, University of Wales, Bangor.nShen, K. C. 1973. Steam-press process for curing phenolic bonded particleboard. Forest Prod. J. 26(11):46-50.n
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