Análise comparativa da secagem de esmalte imobiliário pelo método normativo e por radiação micro-ondas

Abstract

In this work, the drying of synthetic white enamels when subjected to microwave radiation was examined. The new methodology made it possible to speed up, by eight times, the drying time of enamels produced at the Hydronorth S/A paint factory, located in Cambé, in the interior of Paraná. Currently, the company adopts the drying test for synthetic real estate enamels in white and black, which lasts 24 hours, as determined by the ABNT NBR 15311 standard. In this way, the decision to bottle a certain batch of paint depends on the result obtained in this analysis, which can compromise the company's productivity, if it is necessary to retain a batch of non-compliant product in the mixer for this long time. As an alternative to reducing this time, this work proposes the use of a domestic microwave oven to accelerate the drying of enamels, according to a factorial design. The planning was elaborated considering the analysis of the responses color, brightness and drying time responses of a liquid film extended over a substrate when this film is submitted to a certain oven power in a certain time interval. Preliminary tests with three different substrates and thicknesses of applied films, delimited the factorial design, carried out in triplicate and with a central point. The results showed that the exposure time under radiation significantly influences the final color of a dry paint film while the oven power influences the gloss. It was also possible to identify two processes for the formation of the dry film: drying by evaporation of solvents and curing by oxidative polymerization of the phenolic resin, being necessary to determine variables that provide the event of the two phenomena in the most complete way possible, forming the expected film within the predetermined parameters. The drying of five different batches of the product by the normative method and by the new methodology led to the conclusion that, even the results of the color variable being different from those obtained by the norm, the brightness variable presented an efficient correlation between the data, making the method applicable.