Subtropical testing of ACA-treated hardwood particleboard

Flakes of 22 Ghanaian hardwood species (in equal weight proportions) were treated to four retentions of ACA (zero, 0.2, 0.4, and 0.6 pcf, or zero, 3.2, 6.4, and 9.6 kg/m3 based on particleboard volume), and manufactured into phenolic-bonded structural type particleboards using 5 percent or 8 percent resin solids. Stakes from panels were installed in the ground in the Caribbean National Forest of Puerto Rico, and evaluated for assay, and decay and termite resistance after 7 years of exposure. Stakes containing 8 percent resin were preferentially invaded by small plant roots at the groundline. Failure rates after 7 years due to fungal soft rot as well as white rot and brown rot were 95, 100, 77, and 15 percent for zero, 0.2, 0.4, and 0.6 pcf (zero, 3.2, 6.4, and 9.6 kg/m3) ACA, respectively. Rating of stake surfaces for termite attack indicated fair to good performance overall, but internal examination of zero and 0.2 pcf (zero and 3.2 kg/m3) treated stakes revealed extensive termite invasion. Assay results indicated some loss of copper within the first year and negligible loss thereafter. There also was significant loss of arsenic within the first year, and virtually total loss by the seventh year. From deterioration that is present in the stakes remaining after 7 years in field exposure, it is projected that 0.6 pcf (9.6 kg/m3) ACA based on particleboard volume, will probably not provide long-term fungal and insect protection to hardwood particleboards in ground contact in such a high-hazard environment.

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