Comportamento de filmes secos de tintas acrílicas à base d'água em condições de incêndio

Abstract

MACHADO PEREIRA HENRIQUE, ANGELO ABEL. Behavior of water-based acrylic paint dry films under fire conditions. Porto Alegre. 2022. Thesis. Master Graduation Program in Materials Engineering and Technology, PONTIFICAL CATHOLIC UNIVERSITY OF RIO GRANDE DO SUL. The growing availability of new polymeric materials for finishes and coatings used in civil construction, many of them combustible, has driven research to improve the testing protocols of these products, aiming at fire prevention. There are specific standards to determine the flammability of polymeric materials, but there are no specific standards for dry paint films. Most tests analyze the flammability of the paint film considering painting on a substrate, that is, on masonry, wood, or plaster. In addition, there is no simple methodology to estimate the toxic danger of burning paint films used as coatings in civil construction. Most tests for coatings seek to analyze the density of smoke generated by the material during burning and the density of particulates. Given this context, this work aims to quantify the emission of carbon dioxide and carbon monoxide during heating to combustion of commercial brands water-based, white acrylic paint films simulating a fire condition. Several techniques were used (TGA, CG, ICPMS and MEV/FEG) including flammability tests and the collection of gases generated during heating to combustion of the films in a closed oven. In the flammability tests carried out according to NBR 14892 (horizontal method), one of five samples was considered noncombustible and the other four were classified as self-extinguishing. Similar results were obtained in tests in accordance with UL 94 – HB (horizontal method - A). However, in the tests carried out in accordance with UL 94 – V0 (vertical method - B) all films were considered combustible. This discrepancy is not observed in the pyrolysis temperatures, obtained by TGA in synthetic air, which were around 374 °C, for all paints, indicating that complementary methods must be used to obtain flammability in the case of paint films. Gas chromatography analysis, performed with the gases collected in the pyrolysis oven, indicated that from 50 to 200 °C there was no CO emission by inks A, C and E. However, in the range of 50 to 200 °C, the ink B emitted from 198 to 399 ppm of CO and ink D of 371 and 407 ppm of CO. These amounts are above the amount of CO allowed for closed environments by NR 15. Above 50 ppm of CO, the first physiological symptoms appear, such as headache and dizziness. On the other hand, all paint films analyzed showed low CO2 emission rates, less than 3900 ppm, which is the reference quantity of NR 15, and less than 50,000, which is the reference quantity for the beginning of physiological symptoms in environments closed. In view of the results obtained and considering that the maximum temperature that the human body can withstand is 127 °C for 20 min, it is concluded that only paints B and D will contribute to the increase in the toxicity of the smoke generated in a fire.