The effect of organoclays on the fire-proof efficiency of intumescent coatings

Abstract

We explored thermal transformations of the intumescent system (ammonium polyphosphate, pentaerythrite, melamine, copolymer of styrene acrylate) in the temperature range of 200-600 °C in the presence of organomodified montmorillonites and titanium nano-oxide. Coefficients of swelling, masses of coke residues are determined and morphology of the formed coke layer is investigated. These data were used for the development of formulations for effective fire-retardant coatings of the intumescent type, which do not contain halogen fire retardants. As a result of the research, it was established that montmorillonite and organic clays on its base (cetyltrimethylammonium- montmorillonite and tallow bis-hydroxyethyl methyl ammonium-montmorillonite), in contrast to titanium nano-oxide, significantly inhibit the processes of swelling at the initial stages of fire action. At temperatures above 500 °C, the intumescent compositions, which contain organic clays, form a durable and dense coke layer. IR-spectrometric studies of the samples of coke with the participation of organoclays demonstrate deceleration of oxidation processes and decomposition of polymeric protective layer in contrast to the composition with titanium oxide and nano-oxide. Based on these observations, we give practical recommendations regarding the preparation of formulations for fire-retardant coatings for the building structures depending on the required limit of fire resistance. It is recommended to use additives of nano-oxides for the class of fire resistance R 30-R 45; and for the class of fire resistance R 60 and above, organoclay should be added to the intumescent system. This assumption was confirmed by firing tests of steel columns. The results we obtained may be used for the design of new fire-retardant coatings of the intumescent type with improved efficiency and ecological safety.