2994 



Chapter 24 



Species 



Yellow-poplar 

 Southern pine. 



Linear expansion 



Percent 



0.030 



.036 



Panel density 



Lblcu ft 

 39.4 

 40.4 



When northern red oak flakeboard was given OD-VPS treatment, Heebink and 

 Lehmann (1977) found that linear expansion was 0.53 to 0.56 percent; these oak 

 boards were made of cross-grain planed flakes 2 inches long and 0.015 inch 

 thick. Ring-flakes 2 inches long and 0.020 inch thick yielded flakeboards with 

 linear expansion after OD-VPS as follows: 



American elm 0.28-0.33 percent 



Maple sp 0.38-0.40 percent 



Hse (1981) found that linear expansion of a phenol-formaldehyde-bonded 

 white oak flakeboard subjected to the OD-VPS cycle was particularly large 

 (0.528 percent) compared to that of southern red oak flakeboard (0.358 percent), 

 but was significantly reduced by applying polyisocyanate to the flakes before 

 application of liquid phenol formaldehyde resin (table 24-10). 



Heebink and Hann (1959) concluded that addition of 1 percent wax to north- 

 em red oak flakeboard made of 1-inch-long, 0.015-inch-thick, disk-cut flakes 

 did not increase linear stability; their boards were bonded with urea-formalde- 

 hyde resin. 



Table 24-20. — Dimensional stability evaluated by 24-hour water soak of flakeboards of 

 mixed species and single species of southern woods (Data from Price 1978)' 



Panel type Water Linear expansion^ 



and density absorption Thickness swell 8-foot 4-foot 



(Ib/cu ft) direction direction 



Percent Percent Percent/ Percent 



percent 



1/2-in oriented mixed species 



43.63 30.0 20.8 0.338 0.085 0.030 



48.30 36.4 17.8 .383 .079 .020 



1/2-in random mixed species 



43.95 21.4 13.2 .454 .055 .090 



45.68 21.0 13.2 .445 .062 .101 



5/8-in oriented mixed species 



42.54 36.6 22.7 .463 .193 .143 



47.16 27.8 19.0 .351 .190 .129 



5/8-in random mixed species 



38.77 26.7 13.3 .342 .058 .116 



42.03 22.5 12.0 .383 .028 .057 



47.07 17.1 9.6 .428 .065 .085 



1/2-in random pine 

 40.37 27.3 12.9 .331 .020 .053 



1/2-in random yellow-poplar 

 39.42 20.5 9.9 .372 .025 .035 



'See footnote of table 24-12 for flakeboard fabrication procedures. 



^Calipers were used to measure the distance between pins set in grommeted holes. 



