Micro-Distribution of Micronized Copper in Southern Pine
R Stirling, J Drummond, Jun Zhang, R J Ziobro
For copper-based preservatives to be used in ground contact, penetration of copper into the cell wall is believed to be important to protect the wood from soft rot fungi. Preservatives containing soluble copper are known to do this. It is not known whether preservatives containing particulate copper will also migrate into the cell wall in sufficient quantities to control soft rot decay. An AWPA standard E11 leaching test found that leachate from southern pine blocks treated with a preservative containing particulate copper (Micronized copper quat) contained copper ions, suggesting that copper-containing particles in the treated wood slowly release mobile copper. Southern pine sapwood samples treated with wood preservatives containing soluble (ACQ-D) and particulate copper (Micronized copper quat), as well as untreated southern pine sapwood, were analyzed by Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-Ray Spectrometry (EDS). Copper was detected in the lumens of wood treated with both preservatives, and not in the untreated control. Moreover, the presence of small amounts of copper in the cell walls of samples treated with Micronized copper quat and ACQ-D was indicated by ESEM and EDS. This was further supported by the results of a fungal cellar test and a field stake test which demonstrated that wood treated with Micronized copper quat is resistant to soft rot attack. Future work will investigate copper mobility from particles lodged in the lumens.
Keywords: micronized copper, alkaline copper quat, environmental scanning electron microscopy, micro-distribution, cell wall, southern pine