A new benzoxazine-based intumescent coating for passive protection against fire

• Published in: Progress in organic coatings 2019-12, Vol.137, p.105321, Article 105321
• Main Authors: M. Beraldo, Carlos H., da S. Silveira, Mauro R., F. Baldissera, Alessandra, Ferreira, Carlos A.
• Format: Article
• Language: English
• Subjects: Aerospace engineering; Benzoxazine; Benzoxazines; Coatings; Expandable graphite; Fire exposure; Fire protection; Fire resistance; Flame retardants; Intumescent coatings; Melamine; Optical microscopy; Phenolic resins; Scanning electron microscopy; Substrates; Thermogravimetric analysis
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2019.105321

•Only melamine does not cause expansion of the char layer in the adopted system.•Addition of melamine and expandable graphite form a highly porous char layer.•Individual addition of expandable graphite forms a cohesive and protective layer.•Heat released of the paints is related to the amount of benzoxazine in the system.•Expandable graphite exposed to high temperatures may generate graphite oxide. The use of intumescent coatings has proved to be an efficient alternative for the protection of metallic substrates against fire. Benzoxazine is a type of phenolic resin of great interest for aerospace engineering because it inherently exhibits flame retardant properties. However, its use as the main component of an intumescent coating has not been explored yet. The aim of the present work is to develop, for the first time, an efficient benzoxazine-based intumescent coating. The proposed formulations were applied to steel substrates and exposed to fire resistance tests. The coatings were characterised using thermogravimetric analysis (TGA) and microcolorimetry (MCC). The resulting chars were analysed using MCC, optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The intumescent coatings provide efficient fire protection. The substrates coated with the formulations containing expandable graphite showed a decrease of 300 °C when compared to the uncoated substrate. SEM analysis of the char revealed porous structures and MCC showed that benzoxazine coatings have low heat release.