Properties of Medium-Density, Dry-Formed Fiberboard from Seven Hardwood Residues and Bark

In the refining of both white oak cooperage wastes and aspen wood it was necessary to use considerable heat energy and long retention time in order to obtain high quality fiber furnishes in the Bauer 418 refiner. The processing of four hardwood bark species required shorter retention time and consumed less steam pressure and horse power than three hardwood mill residues during the refining process. It was found that processing dry wood residues in a steam-pressurized refiner offers an unexpected energy saving advantage during the subsequent drying operation in dry-formed fiberboard manufacture. Medium density fiberboards at 7.5 and 10.0 percent resin levels meet most of the specifications required for industrial-grade type of board. Fiberboard made from steam-pressure refined furnishes showed better bending strength and tensile strength parallel to face; less variation in linear expansion; and tighter edges than particleboard made from corresponding hammer-milled furnishes. Cottonwood bark fiberboards showed the least average linear expansion values, and are suitable for underlayment or other interior uses. Three other bark boards had good internal bond and screw-holding properties, but lower bending strength. At a 10 percent resin level they can be used in non-structural applications, where high bending strength is not needed. There were more inner bark tissues contained in cottonwood bark as compared to bark from two oaks and a walnut species. Hammermilling tended to break cottonwood bark into thin, flaky particles which contributed to better bending properties of different combinations. Simple regressions explained up to 97 percent of the variation in some board properties. Close associations were found between board properties of stiffness and maximum bending strength, between tensile strength and modulus of rupture, and between face screw holding and edge screw holding values. In spite of a wide range of furnish types, milling techniques, and resin levels involved, relatively reliable approximation of the board properties can be made.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member