Effect of micronized copper treatments on retention, strength properties, copper leaching and decay resistance of plantation grown Melia dubia Cav. wood

Due to the health and environmental concerns, residential usage of copper chrome arsenate (CCA) and similar other heavy metal-based wood preservatives has been restricted in many countries. Waterborne micronized copper formulations of micron-sized particles containing copper- and some biocides are being used on commercial scale to improve the biological durability of various nondurable timber species. In the present work, different concentrations of micronized copper azole (MCA) were used to vacuum-pressure treat the plantation grown non-durable Melia dubia Cav. sapwood. The same species was also treated with CCA and water to be able to compare the efficacy of the treatments. Effect of impregnation of different MCA concentrations (0.5–2.0%) on the retention, density, water uptake, mechanical properties and decay resistance of M. dubia wood against brown and white rot fungi was evaluated. Copper leaching tests were carried out following American Wood Protection Association (AWPA) standards (E11) and the amount of copper leached from treated wood was analyzed using atomic absorption spectroscopy. The amount of copper retention in treated wood increased with increasing MCA concentration. The density of treated wood was slightly increased with MCA concentration due to the increased amount of preservative absorbed, while most of the strength properties of wood treated with MCA were found either comparable to control or slightly reduced. Micron- to nano-sized copper-containing particles were observed on cross-section and in the cell lumens. The numbers of particles observed on wood surfaces increased with the MCA concentrations. The improved performance of micronized copper treated M. dubia suggested that MCA can be used as an alternative to CCA and similar precarious preservatives for extending the service life of non-durable timbers.