Sol-gel coatings with essential oil to prevent fungal defacement on bricks

N. BELLOTTI; R. ROMAGNOLI; C. DEYÁ

Río de Janeiro

Simposio; Latin American Biodeterioration and Biodegradation Symposium LABS 9; 2016

Structural materials used usually outdoor, such as brick, stone and wood, among others, need to maintain their natural appearance in service due to aesthetic reasons. Therefore, usually they are not protected with opaque protective paints. However, structural materials are susceptible to microbiological colonization and bricks have very low resistance to water and high porosity consequently they are more susceptible to bio-deterioration. Especially, molds are generally considered to be one of the major deteriorating agents of buildings materials. Bioactive coatings based on materials obtained by sol-gel process represent a promising option to control biofilm formation. In this sense, the present work proposes the addition of natural products as vegetables essential oils in a siliceous matrix for antifungal protection on bricks base. The essential oils used in this research were commercial ones and correspondent with pine, tea tree and geranium. The sol-gel precursor used was the mercaptopropyltrimethoxysilane (MTMO). The films were characterized by Fourrier transform infra-red spectroscopy and surface tension measurements by the water/ethanol solutions method.The bio-resistant test was carried out using fungi (Aspergillus sp., Alternaria sp. and Cladosporium sp.) isolated from bricks located outside CIDEPINT building, La Plata (27ºS22?0??S and 55º53?36??W). The assessment of coatings bio-resistant against the cited molds was performed on plates following a procedure similar to the fourth weeks ASTM D5590‐00 test. This standard proposes to rate the fungal growth as: 0 none, 1 trace, 2 light, 3 moderate, 4 heavy.Film characterization showed differences in surface wettability, especially between the non-treated and treated samples. FTIR spectra were used to confirm the presence of the essential oils in the film.The results obtained from the bio-resistant test showed that the sol-gel coating control without biocides presented some fungal inhibition with a light fungal growth rate (R) as 2 against Aspergillus sp. and Alternaria sp. but moderate, R=3, to Cladosporium sp.. The adding of 1% of pine and tea tree oils showed improve the performance presented for sol-gel control to light growth R=2 related to Cladosporium sp., the other results were similar to the coating control. Geranium oil did not improve the performance of the control coating with any of the three molds. On the bricks without any protection the fungal growth was heavy with R=4 with the three microorganisms.