Desenvolvimento e avaliação antimicrobiana de revestimentos para madeira plástica a base de PDMS com nanopartículas de prata e de óxido de zinco utilizando Solution Blow Spraying (SBSp)

Abstract

Wood Plastic Composites (WPC) is a polymeric composite with high contents of vegetal fibers. Given the porosity and the biodegradable nature of the fibers, these materials are susceptible to the microbial attack. In order to protect WPC against biological degradation, metallic nanoparticles are antimicrobial agents that have been gaining prominence. In this study, antimicrobial coatings for WPC based on poly(dimethyl siloxane) (PDMS) with silver nanoparticles (AgNPs) and zinc oxide (ZnO-NPs) were developed, using solution blow spraying (SBSp). The AgNPs were synthesized by chemical reduction of silver salts with sodium borohydride, having their nanometric particle size confirmed by ultraviolet-visible spectroscopy and a minimum inhibitory concentration against Pseudomonas aeruginosa and Staphylococcus aureus of 150 µg/mL and 250 µg/mL, respectively. The ZnO-NPs, synthesized in ethanolic medium by the microwave-assisted hydrothermal method, presented wurtzite hexagonal structure and average particle size of 229 nm, determined by dynamic light scattering (DLS). In the agar diffusion test, the ZnO-NPs showed a discrete antimicrobial activity against the two microorganisms mentioned above. The freshly prepared AgNPs colloidal suspension and the ZnO-NPs suspension in ethanolic medium containing 0.5%, 1.0%, 1.5% and 2% (m/v) were sprayed onto the PDMS partially cured surface . In the case of the PDMS/AgNPs coating, the nanoparticles were sprayed 3, 5, 8 and 10 times, with one spray per minute, in order to increase the AgNPs content adhered to the substrate. For the coating of PDMS/AgNPs, the antimicrobial action was higher according to the increase in the number of AgNPs applications. For PDMS/ZnO-NP coatings, the best antimicrobial action results were obtained for the coating containing 0.5% (m/v) of ZnO-NPs. The increase of clusters in the coatings with 1.5 and 2% of ZnO-NPs probably contributed to this result. Therefore, the coatings of PDMS/AgNPs and PDMS/ZnO-NPs have great potential of application in the protection of plastic wood composites from microbial attacks.