Effects of manufacturing parameters on the linear expansion of densified wood composite panels, 3: Effect of board density, resin type and resin contents on linear expansion of medium density fiberboard
2001
Suematsu, A. (Polytechnic Univ., Sagamihara, Kanagawa (Japan)) | Sekino, N. | Fujimoto, Y. | Kitani, Y. | Wang, Q.
The objective was to determine the relationship between the variables of board density, resin type and content, and the dimensional stability properties of medium density fiberboard (MDF). Manufactured boards were exposed to three levels of relative humidity (RH) and a vacuum-water-soak treatment. Changes in moisture content (MC), linear expansion (LE), and thickness swelling (TS) were measured. Results obtained are summarized as follows: 1) Equilibrium moisture content (EMC) decreased with increasing board density and resin content at all levels of exposure. The EMC of urea-melamine (UMF) resin board had a slightly higher value. 2) Increasing board density increased LE per unit of moisture content change (LE/MC) and TS per unit of moisture content change (TS/MC). LE/MC was dependent on resin type. Increasing resin content decreased TS, but had a tendency to increase LE slightly. 3) Multiple regression analysis showed that LE/MC could be predicted with the TS/MC, board density (D), ratio of maximum density through the board thickness (Dmax) and D (Dmax/D), and resin content (RC) as explanatory variables. 4) When exposed to an alternate vacuum-water-soak and oven-dry treatment, TS increased, however LE decreased with increasing number of cycles. The length of the board in the dry condition gradually became shorter than the original length. 5) MDF had larger values of LE/MC than particleboard because of its higher values of Dmax/D.
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