Slash Pine Rootwood in Flakeboard

Flakes 3 inches along the grain, 3/8-inch wide, and 0.02-inch thick, were prepared from the taproots (with six-inch-high stumps) and from the second logs of eight 31year-old slash pines. Forty-four lb./cu.ft. structural boards with random orientation of flakes were prepared with five percent phenol-formaldehyde solids. Stemwood and rootwood boards from each tree were tested for bending strength, internal bond, 6d nail-withdrawal resistance, and dimensional stability. Specific gravity (0.D. weight, green volume) of stems averaged 0.52; rootwood averaged 0.43 and decreased sharply with depth below ground. Stemwood boards were stiffer (737,000 p.s.i. MOE) than rootboards (643,000 p.s.i. MOE), but bending strength was lower (4,800 p.s.i. MOR) for stemboards than for rootboards (5,500 p.s.i. moR). MOE/MOR ratio was 155 for stemboards and 118 for rootboards. The two types of boards did not differ in nail-withdrawal resistance (96 and 97 ibs). Internal bond of rootboards (114 p.s.i.) was almost double that of stemboards (60 p.s.14; this was associated in part with the greater degree of densification of rootwood (x 1.66) as compared with stemwood (x 1.36). Root flakes were more conformable, but had a higher proportion of grain deviation and damaged surfaces. Rootboards had greater dimensional movement in both planes, greater soaked moisture content, and greater thickness springback. Recovery from linear swell was greater for rootboards. By VPS test, stemboards contained 108 percent moisture after soaking, swelled 26.8 percent in thickness (15.2 percent of which was not recovered when redried) and swelled 0.40 percent in length. stemboard strips dried from 5 percent M.C. (no soaking) shrank 0.18 percent in length; they were 0.1 percent shorter than redried soak strips. Rootboards contained 114 percent moisture after soaking, swelled 30.2 percent in thickness (21.7 percent of which was not recovered when redried) and swelled 0.52 percent of length. Strips dried from 5 percent M.C. shrank 0.26 percent in length. Interrelations of board properties differed for the two materials. Differences appear to be primarily due to anatomical characteristics, lower inherent strength of rootwood, degree of densification, and machinability. Wood from the stump-taproot appears satisfactory for particleboards, but partial preliminary breakdown to remove dirt pockets would be advisable.

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