Properties of Particleboard from Southern Yellow Pine and Cottonwood Mixtures

Physical and mechanical properties of medium density, urea formaldehyde particleboards of various mixtures of Southern yellow pine and cottonwood furnish were determined. Resin content, press conditions and furnish were comparable to those currently used in commercial production. Relationships between several properties (MOE, MOR, rail shear strength, plate shear modulus, thickness swell, springback and linear expansion) and percentage of included cottonwood were determined. Correlation coefficients (r) for these relationships were 0.595 to 0.970. All boards met commercial standards for type 1-B-2 particleboard with respect to MOE, MOR, IB, screw withdrawal and linear expansion. Boards containing all cottonwood were found to be 37 percent stiffer (MOE) and 70 percent stronger (MOR) in flexure than boards containing all pine furnish. Boards containing all cottonwood were also found to have 41 percent higher edgewise (plate) shear stiffness and 56 percent higher edgewise (rail) shear strength than boards containing all pine. Thickness swell (from 65 to 90 percent RH) was 29 percent higher and springback (when reconditioned to 65 percent RH) was 38 percent higher for cottonwood boards than for pine boards. Boards containing all pine furnish had 54 percent higher linear expansion (from 65 to 90 percent RH) than did boards containing all cottonwood furnish.

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