Slash pine rootwood in flakeboard

Abstract

Flakes 3 Inches along the grain. 3/8-inch wide, and 0.02 inch thick were machined from the taproots (with 6-inch-high stump) and second logs at eight 31-year-old slash pines. Specific gravity (O.D. weight, green volume) of stems averaged 0.52; rootwood averaged 0.43 and decreased sharply with depth below ground. Forty-four-lb./cu. ft. structural-type particleboards were prepared with random orientation of flakes and 5 percent phenol-formaldehyde solids. Stemwood boards were stiffer (737,000 psi MOE) than rootwood boards (643,000 psi MOE), but bending strength was lower (4,800 psi MOR) for stemboards than for footboards (5,500 psi 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 lb.). Internal bond of footboards (114 psi) was almost double that of stemboards (60 psi); the difference was associated in part with the greater densification of rootwood (x 1.66) as compared with stemwood (x 1.36). Root flakes were more conformable but had higher proportions of grain deviation and damaged surfaces. Rootboards had greater dimensional movement in both planes, greater soaked moisture content, greater thickness springback, and greater recovery from linear swell. Interrelations of board properties differed for the two materials. Differences appeared to be primarily due to anatomical characteristics, lower inherent strength of rootwood, degree of densiflcation, and machinability.

Citation

Howard, E.T. 1974. Slash pine rootwood in flakeboard. Forest Products Journal 24(6):29-35