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Revealing the inner secrets of intumescent chars by advanced small scale tests combined with µ-CT
(2015)
From halogenated flame retardants to non-halogenated to nanocomposites, each milestone in flame retardancy research led to an increase in performance and safety. With the rise of ceramic precursors in flame retardants, a new field of applications in extreme fire scenarios has become accessible. Intumescent coatings combined with precursors for ceramics show a high temperature transition to a ceramic foam, which provides much better fire resistance than conventional coatings at temperatures beyond 1200°C. Even a protection at 2000 °C for several minutes can be achieved. Combining the expansion property of traditional intumescent coatings with a ceramification at high temperatures leads to high-performance coatings, whose unique properties may prove useful for emergency insulation systems for re-entry bodies in the aerospace industry or special fire protection applications.
In this study, the protection performance in extreme fire conditions, the development of the expansion and the following ceramic transition of a high-performance coating are investigated. To this end, a small scale high-performance burner setup was created. The coated (2.5/4 mm) steel plates (75 x 75 x 2 mm) were exposed to direct flame treatment of a propane-oxygen-burner controlled by two flow controllers. During the test, temperatures above of 1800 °C were reached and steel and flame temperature were recorded. Fire tests of different durations (1, 2.5, 5, 10 and 20 min) were performed. The residues of the different development stages were analysed with non-destructive µ-computed tomography and scanning electron microscopy. The 3D images of the computed tomography provide an insight into the developing cell structure and state of ceramification of the residues.