Properties of Structural Particleboards from Douglas-Fir Forest Residues

Structural particleboards bonded with phenolic resin were prepared from forest residues using Douglas-fir and some hemlock-true fir mixtures. Various diameters and proportions of sound wood, dead wood, decayed wood, tops, branchwood, and bark were used. Panels of 40 p.c.f. density, 1/2 inch thick, containing 5 percent phenolic resin and 1 percent wax were prepared, most of three-layer construction using large (0.02 x 1 x 2 in.) disk flakes for faces and 0.02- x 2-inch ring flakes for core material. Faces comprised 30 percent of panel weight and cores 70 percent. Silica content was less than 0.03 percent for wood fractions and was between 0.1 and 0.3 percent for the bark fractions. Ash and silica were concentrated in the bark, small twigs, and needles; thus large quantities of these materials should be avoided to minimize possible panel machining problems. Branchwood with high proportions of reaction wood had much more longitudinal swelling than normal wood. Significant strength reductions were found when more than 12 percent bark was included; when panels were composed entirely of tops and branches; or when panels contained a mixture of residues and were composed of less than 75 percent sound wood. Badly decayed wood reduced strength and durability properties in proportion to the amount and severity of decay. Retention of properties after accelerated aging was generally comparable to results from control panels, except with panels made up of 25 percent bark, 100 percent decayed wood, or 100 percent branchwood. Panels containing large amounts of branchwood had substantially poorer dimensional stability. Panels made with varying proportions of mixed western softwoods were comparable in almost all properties to panels made entirely of Douglas-fir.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member