The effect of furnish moisture content, press closure rate, and panel density of thickness swell and the vertical density profile of a mixed hardwood flakeboard

One-half inch non-oriented flakeboard was manufactured using three levels of furnish moisture content (3, 6 and 9 percent); three levels of press closure rate (20, 60 and 100 seconds); and two levels of panel density (41 and 51 Ib/ft³). Panels were manufactured with seventy percent dense hardwood species. Panels were tested for thickness swell and accelerated aged internal bond using the American Society for Testing and Materials D-1037 24-hour water soak procedure, and the American Plywood Association-Pl standard ovendry-vacuum pressure soak procedure. Process variable levels were used to determine a means of decreasing thickness swell and increasing internal bond in panels manufactured with dense hardwood species. Thickness swell decreased with increasing furnish moisture content, decreasing press closure rate, and increasing panel density. Internal bond decreased linearly as furnish moisture content increased, decreased as press closure rate increased, and increased as panel density increased.

Vertical density profiles were developed for all thickness swell and internal bond specimens. The profiles were then divided into five density regions. The response variables were correlated to the five density regions for profiles developed before accelerated aging and for profiles developed by taking the difference of profiles taken before and after accelerated aging. The strongest correlation was found between the 24-hour water soak internal bond specimens and the core density region of the difference of the before and after accelerated aging vertical density profiles (R--0.75, p<0.01).