Assessment of lignin as a carbon source in intumescent coatings containing polyaniline
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Assessment of lignin as a carbon source in intumescent coatings containing polyaniline A. F. Baldissera, M. R. Silveira, A. C. Dornelles, C. A. Ferreira
American Coatings Association 2020 Abstract Lignin, a vegetable compound, is the second most abundant biorenewable and biodegradable polymer in nature. In this study, the addition of this compound to paints containing ammonium polyphosphate (APP) and expandable graphite as pigments was investigated to improve the fire protection performance of intumescent coatings. The combination of lignin with polyaniline (PANI) in the formulations was also evaluated, as previous studies have shown that PANI-based paints show promising results in intumescent coatings. For this purpose, the thermal protection of mild steel samples coated with these organic coatings was evaluated during a fire resistance test, with the sample exposed to a Bunsen torch. During the test, temperature data and thermography images for the steel surface were collected. The coatings were also evaluated by thermogravimetric analysis and microscale combustion calorimetry. It was found that all coatings formulated provided good fire protection to the steel substrate and the lignin could be a good option to replace nonrenewable sources in intumescent paints, since the sample coated with the paint containing 10 wt% lignin reached 230C after 30 min of assay. In addition, when this compound was used in combination with PANI, the flame protection was even better. The best performance was observed for the paint formulated with combination of 10 wt% lignin and 10 wt% PANI-ES, whose metal substrate temperature was 170C after 30 min of assay. Keywords Lignin, Polyaniline, Coating, Intumescent, Fire protection
A. F. Baldissera (&), M. R. Silveira, A. C. Dornelles, C. A. Ferreira LAPOL/PPGEM, Universidade Federal do Rio Grande do Sul, BP 15010, Porto Alegre, RS 91501-970, Brazil e-mail: [email protected]
Introduction Safety in construction is an ever present concern, and accidents, such as fire, require the development of new materials able to offer better fire protection and thus provide longer escape and rescue times.1 One material that has received great attention is intumescent coatings, which offer thermal protection to structures, including metallic substrates, which are often made of steel. However, steel loses approximately half of its mechanical properties around 500C,2 which can cause collapses and other serious consequences. Intumescent coatings are heat reactive, expanding with the direct action of the flame or heat source and creating a carbonaceous layer that acts as a thermal insulator. For the intumescence to occur, an acid source, a carbon source, and a blowing agent are the three major reactive components required in the coating.3 Often, only the resin itself, or other nonrenewable sources such as pentaerythritol, is used as a carbon source.4 However, depending on the type of resin used, this is not a sufficient source of carbon to form an efficient flame protection carbonaceous layer.
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