Chemical Investigation of 23-Year-Old CDDC-Treated Southern Pine

Abstract

The effect of 23 years' exterior exposure on copper dimethyl dithiocarbamate (CDDC)-treated southern yellow pine was evaluated by the application of solid state analytical instrumentation. Analytical methods including environmental scanning electron microscopy (ESEM), energy dispersive X-ray analysis (EDXA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma (ICP), and atomic absorption spectroscopy (AAS) were used to study CDDC-treated wood. Data from ICP and AAS analysis indicated that about 60% of copper and 81% of sodium dimethyl dithiocarbamate (SDDC) are lost from the 1/8-in. shell of the below-ground portion of the stakes after 23 years' field exposure. The molar ratio of SDDC to copper for freshly treated southern yellow pine is 2:1, while it is reduced to 1:1 after 23 years' field exposure. ESEM micrographs and EDXA data confirm the presence of solids rich in copper and sulfur similar to that of CDDC freshly treated samples. It is suggested that bidentate CDDC is modified to monodentate and bonded to wood to balance the available valence.