2962 Chapter 24 



Table 24-12. — Modulus of elasticity and modulus of rupture of 4- by 8 -foot flake board 

 made from a mixture of southern woods with flakes aligned and randomly oriented' (Data 



from Price 1978) 



Panels were a mix of 20 percent each by weight of hickory, white oak, southern red oak, 

 sweetgum, and southern pine. Flakes were cut 3 inches long from heated wood on a shaping lathe. 

 Face flakes were 0.015 inch thick and core flakes 0.025 inch thick. Flake moisture content, before 

 addition of 6 percent of phenol-formaldehyde resin and 1 percent of wax, was 3 to 4 percent; mat 

 faces were sprayed with 4.32 g of water/ft*^ surface area. Mats were constructed with each face 

 having one-fourth of total weight. Pressed panels had a density of 46 Ib/cu ft based on ovendry 

 weight and volume at 65 percent RH. They were tested after equilibrating at 65 percent RH. 



MOE proved to be significantly related to compaction ratio. Figure 24-30 shows 

 the relationship (black tupelo omitted). Each small increase in compaction ratio 

 yields a significant increase in MOE. 



Efforts to layer flakeboard according to species, e.g. , placing white oak in the 

 core layer and sweetgum in face layers, have not been particularly successful. 

 Best success has been attained by mixing flakes of the species to be used in 

 controlled proportions, and then using this mixture for all layers. Price (1974) 

 demonstrated the strong effect of species mix on MOE. Using lathe flakes of 

 white oak (a very dense wood) and sweetgum (a low-density wood) Price found 

 that if panel density was fixed, MOE was correlated with the species mix (fig. 

 24-3 1). This effect was also observed by Hse et al. (1975) when veneer flakes of 

 sweetgum and white oak were mixed in varying proportions, with results as 

 follows for flakeboard of constant density: 



Proportion of flakes by species 



