Evaluation of silver nanoparticles supported on LTA structures as biocide for waterborneoutdoor-coating

LUCAS EMANUEL MARDONES; ANDREA PEREYRA; MARCIA SOARES LUTERBACH; ELENA ISABEL BASALDELLA

Manchester

Simposio; The 17th International Biodeterioration & Biodegradation Symposium?; 2017

AbstractThe behavior of silver nanoparticles hosted in LTAstructure as biocide additive for waterborne outdoor-coatings in replacement ofcommercial biocides based on isothiazolinones (CIT-MIT-OIT)was assessed.LTA ordered aluminosiliceous framework (NaA zeolite) witha theoretical ion exchange capacity of 7.04 mEq.g-1 (unhydrated base)was synthesized by hydrothermal crystallization. The Ag+ cationswere incorporated into the zeolite cages by ion exchange process. 24wt% silverloaded zeolite was achieved by contacting, under stirring, LTA with 1.0 mol.L-1of AgNO3 in the dark. To obtain non-aggregate silver nanoparticles, chemicalgreen treatment with trisodium citrate (10-1M) at 90ºC wasperformed. Silver cluster formation was detected by the characteristic changeof colour from white to orange. The reduced silver clusters migrated to theexternal zeolite surface and formed larger spherical nanoparticles, whichexhibited an average diameter of 8 nm with a narrow size distribution. The solidswere characterized by SEM, EDS, XRD, and TEM. Waterborne outdoor-coatings based on thermoplasticbinders were prepared using the composite as biocide in increasing concentrations.Coating with 0.15%wt commercial biocide was used as reference. Styrenatedacrylic binder and elastomeric acrylic emulsion were selected to provide goodelasticity and barrier properties. TiO2 (rutile grade) was used ashiding pigment. Micronized CaCO3 was selected as extender. The pigmentvolume concentration (PVC) of coatings was 33% (12% superior to the criticalvalue). The antimicrobial activity of the dry coating films against P.aeruginosa after 6 months of outdoor exposure was determined. Coatings containingsilver-zeolite composite show excellent antibacterial efficiency.