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.

Zinc borate has long been used as a protector for wood products due to its fungicide, insecticide and flame retardant properties. In this initial study, its capacity as a flame retardant when applied to Eucalyptus grandis wood is evaluated; micronized zinc borate, synthesized from zinc oxide and boric acid in our laboratory was used. The methodology used in the study is the use of the Vandersall tunnel, which allowed analyzing parameters such as the flame spread, the carbonization index, the carbonization area and the wood weight loss. The results show a remarkable improvement in these parameters after the application of micronized zinc borate. For the longest fire exposure time, the percentage decrease of each evaluated parameter is, for tangential and radial plane respectively: 31.27-43.00% for flame spread, 36.66-40.86% for carbonization area, 33.01-52.49% for carbonization index and 19.86-57.80% for mass loss.

The biological decomposition of lignocellulosic materials caused by basidiomycetes plays an essential role in the carbon cycle. Brown rot fungi represent important agents in the biodegradation of wood products and standing coniferous trees in natural ecosystems. The initial moisture content of the wood is an important factor in the degradation process. In this work, the effects of initial moisture content of Eucalyptus grandis sapwood on decay by two brown rot fungi Gloeophyllum trabeum and Laetiporus sulphureus were studied over a 10-month period. The fungal activity was evaluated, through wood weight loss, moisture content, anatomical changes (scan electronic and fluorescence microscopy) and Fourier-transform infrared spectroscopy. Weight loss increased through the 10-month test for both fungi, Laetiporus sulphureus producing higher mass losses. Colonization of the wood by both fungi started below the fiber saturation range. It was observed that the initial moisture content of the wood influenced the rate of deterioration: the wet samples showed higher weight loss compared to the dry samples. Changes in the chemical composition and structure of cell walls were detected. The initial moisture content of the substrate affected the development of the fungi, slowing their growth.

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