Evaluation and Process Optimization of Micronized Copper Azole for Environmentally Sustainable Wood Preservation

Abstract

Micronized Copper Azole (MCA) is a commonly used wood preservative in Canada for pressure-treated products such as decking and fence boards. This research addressed concerns about its treatment process and long term performance. During treatment, preservative dripping from freshly treated wood was frequently observed, creating safety risks for workers and increasing the potential for environmental contamination. This problem was addressed by optimizing the treatment parameters, resulting in a significant reduction in dripping. The environmental impact of MCA was further assessed through a leaching analysis of treated wood exposed to simulated rainfall. Although optimization of the treatment cycle reduced leaching, the wood preservative levels in the leachate still did not meet government regulatory standards, indicating the need for further investigation. Another key issue examined in this research was the presence of black residue on the surface of treated wood, which negatively affected the product’s appearance and quality. An in-depth analysis of the chemical composition of the MCA solution from these treatment facilities revealed considerable variability in preservative composition. Miscibility tests further showed poor compatibility among MCA ingredients, leading to improper mixing, surface defects, and consequently, unsatisfactory quality of the treated wood products. These observations were supported by contact angle and surface tension measurements, which confirmed inadequate miscibility and wettability of the MCA solution. To improve miscibility, four surfactants were selected and evaluated for their effects on contact angle, surface tension, and solution quality: Ammonium Sulfate, TERGITOLTM 15-S-9, TERGITOLTM LFE-635, and a proprietary surfactant. Among these, TERGITOLTM LFE-635 was identified as the most effective surfactant for improving wettability and overall performance of the MCA solution. Finally, efforts were made to analyze how particle size varied with treatment parameters using a laser particle size distribution method. However, this approach was not feasible at this stage due to the complex solution composition and the absence of an accurately estimated refractive index (RI) for the MCA suspension. In summary, this thesis identified key challenges in applying Micronized Copper Azole as a wood preservative and proposed practical approaches to improve treatment efficiency, preservative performance, and the overall quality of wood products treated with MCA.