Table 16 . --Comparative screen analyses of 0.20 inch thick disk flakes (nonhammermilled) 

 and ring flakes produced from sound and decayed Douglas-fir forest residues 

 (greater than 4 inches diameter) (Lehmann and Geimer 1974) 





: Mean screen 



fraction 





: Ring flakes from hand- 



: Disk flakes 



Screen rnesh 



: cut fingerlings 



: (nonhammermilled) 



(inches) 



: (Sound) (Decayed) 



: (Sound) (Decayed) 



Percent 



>l/2 15.4 11.4 84.7 60.1 



<l/2 >l/4 40.6 29.6 8.6 22.4 



<l/4 >l/8 18.2 18.1 3.0 9.5 



<l/8 >1/16 12.7 18.5 2.0 5.4 



<1/16 13.2 22.4 1.7 2.6 



Homogeneous random flakeboards were prepared employing 3 percent phenol -formaldehyde 

 resin and 1 percent wax. The physical properties of the panels were evaluated and com- 

 pared to assess the influence of flake type. Physical properties (before and after 

 accelerated aging) are given in table 17. Distinct reductions in strength are evident 

 when compared to similar panels produced from wholly sound wood (table 14) , and again 

 are attributable to lower wood quality used in panels shown in table 17. Levels for 

 MOR, MOE , and IB (internal bond) for many panels still exceed current Canadian and 

 American standards given in table 12. 



Panels made from various kinds of flakes are compared in table 17. Ring-flake 

 panels generally have reduced MOR and MOE levels compared to disk-flake panels, but IB 

 is similar. Ring flaking hand-chipped fingerlings produces flakes that are inferior 

 to those from disk flaking, but drum-chipped fingerlings induce a further reduction in 

 ring flake quality (Heebink, and others, in press) . Panel stiffness (MOE) again appears 

 most sensitive to the difference in quality of ring flakes from hand-cut fingerling 

 and drum-chipped fingerlings. No difference in linear expansion or thickness swell was 

 detected between ring flakeboards and disk flakeboards. 



To consistently obtain panels of maximum strength from ring flakes derived from 

 forest residue, the flakes must be further separated during screening and the longest 

 flakes placed in the panel surfaces. 



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