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Chapter 23 



I 



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 5 



BOARD THICKNESS 





Figure 23-53. — Typical density profile of SIS hardboard. (Drawing after Spalt 1977. 



The obvious major advantage of dry process fiberboards, very large reduction 

 in process water, is increasingly important in light of stringent regulation of 

 effluent quality. 



Another important advantage of the dry fiberboard process is its ability to 

 make medium-density boards thicker than !/2-inch, the upper limit for wet- 

 processing. This allows dry-process fiberboard to compete in a market pre- 

 viously dominated by particleboard. This medium-density, thick, dry-formed 

 fiberboard, normally called MDF, combines dry-process hardboard and parti- 

 cleboard technologies to make a very versatile board product. 



Dry process fiberboards may be classified as thin boards (<y8-inch) and thick 

 boards (>y8-inch). The thin boards are similar to wet-process fiberboard in 

 appearance and applications, and are sold under the same commercial standards. 

 They are made in both medium-density (40 to 50 pounds/cu ft) and in the high- 

 density range (over 55 pounds/cu ft). Thick boards are made only in the medium- 



