Effect of Several Production Variables on Modulus of Rupture and Internal Bond Strength of Boards Made of Green Douglas-Fir Planer Shavings

Using planer shavings from Douglas-fir (Pseudotsuga menziesii), boards were made with variables as follows: three specific gravity levels, 0.60, 0.75, 0.90; three wax levels, 0 percent, 0.75 percent, l.5 percent; three resin levels, 2 percent, 4 percent, 8 percent; and two screen fractions, and -4. The main effect of screening fractions on MOR was that the are stronger than the -4. MOR increased with increase of resin. This gain in MOR was greatest at higher density levels and higher wax levels. If strength was compared by an internal bond, test, the finer size gave higher strength. The effect of wax exceeded that of resin in contributing strength to the board especially with coarse particles at 2 percent resin. Internal bond was found to be a worthwhile adjunct to the modulus of rupture test in interpreting the results.

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