Black-stain Resistant Acrylic Latexes for Wood Coatings Applications
G Boivin, A M Ritcey, P I Morris, V Landry
Translucent coatings on wood in exterior applications often fail due to photodegradation and colonization by black-stain fungi and require frequent refinishing. This limits competitiveness with alternative materials. In this project, it was hypothesized that an effective dispersion of inorganic nanoparticles will provide a translucent coating with long-term resistance to black-stain fungi. Functionalized silver nanoparticles with a mean particle size of 12 nm were incorporated in acrylic polymer particles by miniemulsion polymerization. This polymerization technique has been selected over the traditional emulsion polymerization to encapsulate inorganic particles into polymer particles and prevent the agglomeration of inorganic nanoparticles. In previous work, it was found that latexes containing silver nanoparticles showed antifungal activity against Epicoccum nigrum, and a mix of Penicillium funiculosum and Aspergillis niger at low silver concentration (0.1% m/m) (Boivin, Ritcey and Landry, 2015). Based on these results, acrylic latexes containing different concentrations of silver nanoparticles were mixed with a commercial acrylic resin. The formulations were applied on ponderosa pine (Pinus ponderosa) sapwood and fungal resistance was evaluated against three species Aureobasidium pullulans, Sclerophoma pityophila and E. nigrum. Latexes with concentrations of silver nanoparticles as low as 0.03% were able to control S. pityophila and E. nigrum, while higher concentrations were needed to control A. pullulans.