Hardboards from Mixed Tropical Hardwoods

Forest products users selectively exclude most wood species growing in the natural tropical forests because they are believed to be undesirable by reason of either product quality or processing problems. This study was undertaken to establish the suitability of using mixed tropical hardwoods in the manufacture of medium- and high-density hardboards. Logs from secondary hardwood species were collected in Columbia, Ghana, and the Philippine Islands and shipped to the U.S. Forest Products Laboratory, Madison, Wis., where chip mixtures were prepared to represent run-of-the-woods situations. All of the chip mixtures were readily fiberized in a pressurized refiner, producing an excellent fiber. High-density hardboards made from all chip mixtures by the dry- and wet-forming procedures met the Voluntary Product Standard for standard hardboard, except for some dry-formed hardboards with 2 percent resin. Dry-formed, medium-density hardboards were made from all chip mixtures with urea and phenol-resorcinol adhesives. The urea-bonded hardboards were intended for interior applications and had strength properties that made them suitable for the manufacture of furniture. The phenolresorcinol-bonded hardboards were sufficiently durable for exterior applications and had strength properties suitable for use as siding. All classes of hardboards from all chip mixtures had excellent dimensional stability with very small linear and thickness movement. The surfaces of all hardboards were excellent, and would be suitable for finishing operations.

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