The Effects of Copper-Based Preservative Technologies on the Resistance of Aspen Strandboards to Biological Degradation

Mold and decay resistance of aspen strandboards treated with various copper-based preservative systems were evaluated in laboratory tests. Five copper-based chemicals or zinc borate were blended into the aspen furnish at three retention levels. Tebuconazole or 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one (DCOI) were added as cobiocides to selected copper-based treatments. Panels were inoculated with four common molds and subjected to high temperature and humidity for 8 wk according to AWPA Standard E24. Most panels experienced extensive mold growth, but panels treated with DCOI had marked resistance to attack as did combinations of copper-based preservatives and DCOI. Panels were also assessed for decay resistance in a laboratory soil-block test against the brown-rot fungus Gloeophyllum trabeum or the white-rot fungus, Trametes versicolor, according to AWPA Standard E10. All preservatives reduced weight losses caused by G. trabeum or T. versicolor below 10%, except for micronized copper hydroxide or DCOI alone. The four other copper-based preservatives performed well independently and with the addition of DCOI or tebuconazole. The results suggest that incorporating combinations of copper-based preservative systems with organic cobiocides improved decay and mold resistance of aspen-oriented strandboard