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Chapter 23 



COMMERCIAL MEDIUM-DENISTY FIBERBOARDS 



Standards. — Property requirements of thick medium-density fiberboard for 

 interior use are specified in a standard co-sponsored by the American Hardboard 

 Association and the National Particleboard Association; some major require- 

 ments from this standard are shown in table 23-17. 



Properties. — Suchsland et al. (1978) evaluated properties of eight commer- 

 cial medium-density fiberboards, from a total of 1 1 such boards being manufac- 

 tured at time of test in 1975 (table 23-18). They found that average board 

 densities varied among manufacturers from about 0.72 to about 0.95 g/cm^ and 

 also varied significantly within board type (fig. 23-107). 



They found that most boards had considerable density variation in cross 

 section, faces being denser than cores. Enhancement of modulus of elasticity in 

 bending provided by this density gradient is shown in figure 23-108 in which the 

 density variation of each board is represented by a horizontal line at the level of 

 its modulus of elasticity. The length of each line indicates the density gradient 

 from face (right end of line) to core (left end of line), and average board density 

 is indicated by the numbered circle between extremes. Face density appeared 

 strongly correlated with modulus of elasticity in bending. A similar relationship 

 between core density and internal bond strength in tension perpendicular to the 

 face was not found. 



1.0 



DENSITY (G/CM') 



Figure 23-107. — Normal distribution curves for board densities of eight commercially 

 manufactured medium-density fiberboards. (Drawing from Suchsland et al. 1978.) 



