Structural Flakeboards and Composites 2969 



Hse and Koch^ amplified this observation in a sub-experiment in which both 

 surfaces of a mat were sprayed with water (10 grams to each face of a 20- by 20- 

 inch mat) just prior to hot pressing. When a three-layer mixture of hardwood 

 flakes was pressed to stops in 45 seconds to yield a panel density of 50 Ib/cu ft, 

 this water spray raised MOE about 100,000 psi (fig. 24-35). The increase in 

 MOE was mainly attributable to densification of surfaces; density profiles were 

 not quantitatively evaluated, however. Similar observations have been made by 

 Klauditz and Rackwitz (1952), Strickler (1959), and others. 



Inclusion of southern pine in the furnish. — The McMillin-Koch experi- 

 ment^ included observations of boards made of loblolly pine as well as those 

 made of mixed hardwoods (25 percent sweetgum, 50 percent red oak, and 25 

 percent hickory). It was abundandy evident that the pine yielded boards of 

 greater MOE than did the mixed hardwoods. Moreover, while the pine board 

 showed positive correlation between MOE and panel specific gravity, the slope 

 of the regression line was less steep than that for the mixed hardwood board (fig. 

 24-36). 



From these observations and from figure 24-38, it was concluded that a small 

 proportion of pine would substantially improve MOE, internal bond strength, 

 and modulus of rupture at panel densities below 50 Ib/cu ft. 



Inclusion of baldcy press in the furnish. — On the coastal plain of the South- 

 eastern States, baldcypress {Taxodium distichum var. distichum) is an important 

 component of forests. It has lower specific gravity than any of the major species 

 of hardwoods that grow among southern pines, except for yellow-poplar. Me- 

 chanical properties of baldcypress are not greatly different from those of yellow- 

 poplar. Baldcypress is somewhat denser, stronger, and stiffer than aspen 

 {Populus tremuloides Michx.). Flakeboards comprised of one-third baldcypress 

 and two-thirds mixed southern hardwoods have modulus of elasticity at 41 to 43 

 pounds/cu ft panel density of about 700,000 psi (table 24-13).*^ 



Seven-species mix of bottomland hardwoods. — Figure 24-33 summarizes 

 the relationship between panel density and modulus of elasticity of 7/16-inch 

 flakeboard comprised of hardwood species typically found in south-central 

 Louisiana. With 3-inch-long flakes in face and core layers arranged so that face 

 flakes were 0.015-inch thick and core flakes 0.025 inch thick, modulus of 

 elasticity exceeded 700,000 psi at board densities above 41 pounds/cu ft."^ 



This seven-species mixture, bonded with liquid resin and comprised as de- 

 scribed above of flakes cut from hot wet wood on a shaping lathe, had mechani- 

 cal properties generally superior to boards made of other mixes of Louisiana 

 hardwood species, other flake types and dimensions, or with powdered resin 

 (table 24-14).'^ 



Hse, C.-Y. and P. Koch. 1974. Properties of hardwood exterior flakeboard made from flakes 

 prepared on a veneer lathe and on the Koch lathe. U.S. Dep. Agric, For. Serv., South. For. Exp. 

 Stn., Alexandria, La., Fin. Rep. FS-SO-3201-2.66, dated Dec. 31, 1974. 



*^Hse, C.-Y., and E. W. Price. 1982. Technical feasibility of structural flakeboard made with 

 north Florida hardwoods and cypress. U.S. Dep. Agric, For. Serv., South. For. Exp. Stn., 

 Alexandria, La., Fin. Rep. FS-SO-3201-24. 



^Price, E. W., and C.-Y. Hse. 1982. Technical feasibility of a structural flakeboard made with 

 south-central Louisiana hardwoods. U.S. Dep. Agric, For. Serv., South. For. Exp. Stn., Alexan- 

 dria, La., Fin. Rep. FS-SO-3201-20. See also: Price, E.W. and C.-Y. Hse. 1983. Bottomland 

 Hardwoods for structural flakeboards. For. Prod. J. 33 (11/12): 33-40. 



