Preservation of Particleboard and Hardboard with Pentachlorophenol

Three methods of preserving composition board were attempted in the laboratory: 1) spraying the processed wood chips with aqueous sodium pentachlorophenate just prior to adding the adhesive, 2) adding pentachlorophenol or sodium pentachlorophenate to the sizing agent, and 3) adding pentachlorophenol or sodium pentachlorophenate to the adhesive. The most satisfactory method of preserving particleboard bonded with either phenol-formaldehyde or urea-formaldehyde resin was by direct addition of sodium pentachlorophenate to the adhesive. The amount of sodium pentachlorophenate necessary to achieve protection in a modified soil-block test for both particleboard and hardboard was less than 0.65 percent, based on the dry wood weight. With the addition of as much as 1.0 percent sodium pentachlorophenate, added directly to the resin and based on the dry wood weight, no loss of flexural strength was noted in particleboard. Also, the addition of the sodium pentachlorophenate did not affect water-absorption or thickness-swelling properties over a 24-hour soaking period. Comparative strength and water-absorption properties have also been observed for preserved hardboard. The preservative may be added to the particleboard or hardboard during the manufacturing process at little additional cost over that of the preservative itself.

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