2835 



BOARD DENSITY (LBS/ FT 



Figure 23-65. — (Top curve) Relationship between bending strength and density of hard- 

 board. Drawing after Kumar 1958. (Bottom curve) Percent change in bending strength 

 per 1 -percent change in hardboard density. (Drawing from Suchsland and Woodson 

 1985.) 



may further improve controls on resin content to meet internal bond require- 

 ments and develop press cycle designs for density profiles to improve edge 

 machinability; such considerations are of less than secondary importance in 

 other dry fiberboards. 



A typical process flow diagram for a medium-density fiberboard plant is 

 shown in figure 23-67. This schematic differs little from the dry-process hard- 

 board flow diagram in figure 23-54 but has three unique elements, described by 

 Raddin and Brooks (1965). 



First, a pulp of very low bulk density (2 pounds/cu ft or less) is required to 

 develop good fiber bonds during compression to normal board density (45 to 50 



