Bark as a Supplement to Wood Furnish for Particleboard

Strength properties of laboratory-fabricated homogeneous particleboard of medium density were evaluated to determine the effects of substituting bark for 5, 10, and 20 percent (OD weight) of standard wood furnish. Three types of bark (Douglas-fir, ponderosa pine, and red alder) were individually substituted. The resulting boards, an equal number bonded with urea-formaldehyde (UF) resin and phenol-formaldehyde (PF) resin, were compared to each other and to control boards (100 percent wood furnish bonded with either resin) for differences in physical properties. Red alder bark with PF resin improved IB strength from 6 to 15 percent. Adding ponderosa pine bark with PF resin improved linear expansion and thickness swelling, with these decreasing as much as 18 and 35 percent, respectively. Douglas-fir bark added at the 5 percent level with PF resin did not affect strength properties. Otherwise, the three barks performed similarly. Increasing the rate of bark substitution linearly decreased strength properties, but had little effect on dimensional stability. On the average, increasing the rate of bark substitution from 5 to 20 percent decreased MOR 7 to 24 percent, decreased MOE 4 to 17 percent, and decreased IB 5 to 20 percent.

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