Prevention of the color changes in waterbone antimicrobial coatings with nano-functionalized siliceous filler

LEYANET BARBERIA ROQUE; ERASMO GÁMEZ ESPINOSA; MARISA VIERA; NATALIA BELLOTTI

Ciudad Autónoma de Buenos Aires

Congreso; Midterm Meeting of the International Color Association (AIC 2019); 2019

International Colour Association

In environmental engineering, biodeterioration is defined as any change made by an organism on a surface. These changes can be caused by the mere presence of the organism as well as the result of its metabolic activity and can affect both the appearance and the structure of the materials, as well as potentially damaging to human health. One of the main alternatives to avoid it is the use of coatings with protective characteristics conferred by antimicrobial additives. Nanoparticles are promising to be used as antimicrobial additives, especially if they are obtained by green synthesis, due to be a low cost and eco-friendly methodology. However, the nanoparticles are colored and their addition causes changes in the color of the coatings. The change of color could be considered a useful visual indicator of the loss of efficiency to this kind of functional coatings This effect can be maintained and even increase over time, due to the fact that the nanoparticles are very reactive and tend to aggregate, losing the properties conferred by their nanometric size and shape. These changes in the properties of the coatings would be related to a decrease in their bioactivity. In addition, the ornamental, artistic or functional value that gave the original color to the painted material deteriorates. The objective of this work is to evaluate the effectiveness of the addition of Ag nanoparticles in natural siliceous base material to prevent the change of color of the coating. The adsorptive capacity of Ag+ ions of the siliceous material (SM) was evaluated. To functionalize the SM, it was first activated with an alkaline solution later two strategies were used: the direct addition of silver nitrate 10-2M solution (SMAg) and the addition of silver complexed with ammonium (SMAgC). Afterward, the silver was reduced using the aqueous plant extract of Senna occidentalis from Nigeria. At the same time, the green synthesis of free nanoparticles (AgNps) was carried out using the same silver nitrate solution and the plant extract as a reducing agent. The obtained products were incorporated into a waterborne acrylic paint and applied on slides. The painted glasses were subjected to a natural aging process, exposed to natural light from behind a window. During this time the color was measured by the CIELab system with a colorimeter. Statistical analysis of the color data showed from 24 hours the effectiveness of the functionalized materials to decrease the color change. This data is consistent with the highest antimicrobial activity of the paints with less color variation. The color variation in the control paints was slight. The alternative paints with SMAg and AgNps were big and very big taking into account the colorimeter method by Teichmann. However, with the addition of SMAgC, the color change was barely evident. The color variation over time highlighted the effectiveness of the SMAgC to prevent the color change by approximately six months