CONICET | Buscador de Institutos y Recursos Humanos

The behavior of silver nanoparticles hosted in LTA structure as biocide additive for waterborne outdoor-coatings in replacement of commercial biocides based on isothiazolinones (CIT-MIT-OIT) was assessed.LTAordered aluminosiliceous framework (NaA zeolite) with a theoretical ion exchange capacity of 7.04 mEq.g-1(unhydratedbase) was synthesized by hydrothermal crystallization.The Ag+cations were incorporated into thezeolitecages by ion exchange process. 24wt% silver loaded zeolite was achieved by contacting, under stirring, LTA with 1.0 mol.L-1 of AgNO3 in the dark. To obtainnon-aggregate silver nanoparticles,chemical green treatment with trisodium citrate (10-1M) at 90ºC was performed.Silver cluster formation was detected by the characteristic change of colour from white to orange. The reduced silver clusters migrated to the external zeolite surface and formed larger spherical nanoparticles, which exhibited an average diameter of 8 nm with a narrow size distribution. The solids were characterized by SEM, EDS, XRD, and TEM.Waterborne outdoor-coatings based on thermoplastic binders were prepared using the composite as biocidein increasingconcentrations.Coating with 0.15%wt commercial biocide was used as reference. Styrenated acrylic binder and elastomeric acrylic emulsion were selected to provide good elasticity and barrier properties. TiO2(rutile grade) was used as hiding pigment. Micronized CaCO3 was selected as extender. Thepigment volume concentration (PVC)of coatings was 33% (12% superior to the critical value).The antimicrobial activity of the dry coating films against P. aeruginosa after 6 months of outdoor exposurewas determined. Coatings containing silver-zeolite composite show excellent antibacterial efficiency.

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