Performance of Waterborne Cu(II) Octanoate/Ethanolamine Wood Preservatives

Abstract

Summary Various aqueous wood preservative solutions containing Cu(II) in the form of copper(II) sulphate or copper(II) octanoate, ethanolamine and in one case octanoic acid were investigated by spectrophotometry, polarography and Electron Paramagnetic Resonance (EPR) spectroscopy. Results have shown the same coordination environment around Cu(II) in all solutions with ethanolamine. Computer simulation of the EPR spectra also revealed that the coordination in the first coordination sphere of copper is the same at low concentration of ethanolamine. At 20% ethanolamine concentration, a mixture of two complexes (one with two nitrogens and the other with three) could be detected. The active compound in the investigated ethanolamine containing solutions is the same when previously synthesised copper(II) octanoate was used, or when copper(II) sulphate and octanoic acid were utilized instead. Fungicidal and leaching experiments with the treated wood resulted in the same conclusion: it is not necessary to use pre-synthesised copper(II) octanoate for the preparation of waterborne copper/ethanolamine wood preservatives. Preservative preparation time and costs can be reduced by simply dissolving copper(II) sulphate and octanoic acid in aqueous ethanolamine solutions.

Relationship between copper species in solution and leaching from alkaline copper quat (ACQ) treated wood

“…This may be because of the lower cation exchange capacity at the lower pH even more CuCO 3 (s) may form and contribute to the total amount of leach resistant Cu (Figure 2b). The higher percentage of Cu leached from ACQ at pH 12 compared to pH of 8 and 9 can be explained that the neutral complex, [Cu(Mea) 2-2H ] 0 , has lower affi nity to interact with wood and is available for leaching in agreement with Zhang and Kamdem (2000a) and Humar et al (2003Humar et al ( , 2005 . The monovalent cationic complex, [Cu(Mea) 2-H ] 1 + and CuCO 3 (s) are the major Cu species contributing to fi xation at pH 9 and below (Figure 2b and c).…”

“…For Cu-Mea complexes, the neutral complex fi xes less in wood and contributes to more Cu leaching (Zhang and Kamdem 2000a ;Humar et al 2003 ). Displacement of the Mea ligands is diffi cult because of the high stability of the complex (probably the result of strongly coordinating chelating Mea -ligands); the neutral complex also lacks electrostatic attraction towards the anionic sites.…”

Effect of ammonia addition to alkaline copper quaternary wood preservative solution on the distribution of copper complexes and leaching

“…The proportion of neutral Cu-Mea complex, wCu(Mea) 2-2H x 0 , which has a lower affinity to wood components (Zhang and Kamdem 2000a;Humar et al 2003) compared with the cationic complex species, increases in ACQ solutions with increasing pH. At pH 10.5, there is no change between ACQ 1:4:0 (no ammonia) and ACQ 1:4:2 in the neutral complex distribution; however, further increases in the ammonia to ratios of ACQ 1:4:4 and ACQ 1:4:6 decrease the neutral Cu-Mea complex (Figure 1a).…”

“…This should maximize the capacity of wood to accommodate more reacted Cu compared with Cu-ammonia complexes, which react with wood by consuming two reactive sites in wood (Xie et al 1995;Ruddick 1996). However, neutral Cu-Mea complexes present at higher pH (Tauler et al 1986) in Cu-Mea solution, are less fixed in wood and contribute to higher Cu leaching (Zhang and Kamdem 2000a;Humar et al 2003Humar et al , 2005. The neutral Cu-Mea complex is highly stable as both ligands are strongly chelated with Cu because of the presence of negatively-charged oxygen (dissociated alcohol group) in the Mea ligand and a lack of electrostatic attraction towards the anionic sites.…”

Lastnosti bukovine in njena raba

“…S primerno konstrukcijo ter rabo so dosegli, da bukovina v suhih klimatskih pogojih lahko služi tudi do 300 let. Danes je mogoče njeno biološko odpornost izboljšati s kemijskimi zaščitnimi sredstvi in toplotno obdelavo, sodobne raziskave pa so še naprej usmerjene v podaljšanje njene življenjske dobe Humar & Pohleven, 2005;Humar et al, 2003). Mehanske lastnosti impregniranega lesa se v splošnem bistveno ne razlikujejo od naravnega, modul elastično-sti pa se lahko celo rahlo poveča.…”