Providing moisture and fungal protection to wood-based composites

The use of wood-based composites in structural applications is often limited because of their sensitivity to excessive levels of moisture and decay. The environmental conditions that exist in certain use categories can be so adverse that the performance of these composites is negatively affected. This paper discusses the evaluation of various water-repellent preservative systems as furnish treatments for a single-layer strandboard. After treating aspen strands and fabricating them into composite panels, we conducted physical, mechanical, and efficacy property tests on specimens cut from the experimental panels. The panels were tested for thickness swell, water absorption, modulus of rupture, and modulus of elasticity. Efficacy performance was evaluated in bioassay tests against deuteromycete and basidiomycete fungi. One of the waterbased treatments (WB-1) substantially improved the water-resistant properties of these panels. The thickness swell of control samples after 24 hours of water soaking was 23.8 percent compared to a thickness swell value of 8 percent for treatment WB-1. Similar results were obtained for the water absorption test. No significant deterioration in static bending properties was observed. Our studies showed that a water-repellent preservative system could be effectively applied to furnish that is subsequently used in strand panel production. The physical and fungal resistance properties of the panels were enhanced without decreasing their mechanical properties.

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