Effectiveness of micronizing zinc borate to improve its fungicidal properties

Abstract

The effectiveness was evaluated for an established wood preservative, zinc borate, prepared in an agitating bead mill to extensively reduce its particle size. The generated micro- or nano-particles of zinc borate were characterized by X-ray powder diffraction, and the particle size distribution was determined to evaluate the effect of milling. Then the fungicidal effectiveness of the zinc borate of both milled and unmilled samples were assayed against brown- and white-rot fungi, on culture medium and on conifer and hardwood as substrates. Treated wood samples were subjected to leaching tests. Scanning electron microscopic images of wood samples were examined to analyze the distribution of zinc borate within the wood. The micronized zinc product kept its crystal structure intact, and it increased the proportion of particles with diameters below 100 nm by 25% when compared to the unmilled product. Malt extract-agar medium supplemented with 2.5% of w/w milled and unmilled zinc borate inhibited fungal growth tested. Both milled and unmilled zinc borate protected the wood when not subjected to leaching. The milled sample of zinc borate improved resistance to leaching, which would allow its application in environments of high moisture content; however, it did not improve the fungicidal action against decay fungi.

Ammoniacal Zinc Borate for Wood Protection against Fungi and Insects

“…The retention values do not differ between species, and are generally close to [50] or higher than [37] reported in the literature for analogous treatments on other pinus. Differences in anatomy and density between the used hardwood and the pinus result in lower retention values on the former [35] and with lower ammonia content [39]. However, the ammonia seems to improve retentions, explaining the results.…”

“…The vacuum-pressure-vacuum impregnation of Populus sp., despite reaching greater retention, does not result in a better performance against fungi when compared with vacuum-vacuum impregnation [39]. Ammoniacal ZnB applied by vacuum-vacuum to P. taeda and E grandis wood is effective against xylophagous fungi.…”

“…ZnB has low solubility in water at room temperature-0.28% (w/w) [33]-which makes it hard to apply to solid wood. Many strategies have been developed to counter this, such as synthesizing ZnB in stages within the wood [34], and the use of milled micrometric ZnB [35] or nanometric products [36][37][38]. The use of ammoniacal ZnB improves penetrability in various types of solid wood.…”

“…was chosen for its availability, its treatability and its low natural durability against fungi and insects. The first study in our laboratory verifies the general effectiveness against fungi of ammoniacal zinc borate applied by the vacuum-vacuum (V-V) method by evaluating the susceptibility of the treated wood to fungal decay [39]. Herein, we analyze whether application by vacuum-pressure-vacuum (V-P-V) improves the fungicidal properties of ammoniacal ZnB.…”

Recent Developments Studies on Wood Protection Research in Academia: A Review

“…For instance, Zhang et al (2012) created a micronized boron preservative that had both wood preservative and flame retardant composition with low leachability. In Uruguay, the developed micronized zinc borate inhibited mold growth and prevent leachability while maintained protection against decay fungi (Ibañez et al, 2019).…”