The effect of ammonium polyphosphate:melamine:pentaerythritol ratio on the efficiency of fire protection of reactive coatings

Abstract

In order to optimize the formulation of fire protective coatings for metal constructions, the effect of the ratio of main components in an intumescent system "ammonium polyphosphate–melamine–pentaerythritol" on the thermal destruction of the coating under conditions of fire (200–8000C) has been investigated. Thermal transformations of coatings were studied both by thermogravimetry with stepwise determination of the expansion coefficient by temperature variation and by IR spectroscopy. It was established for the first time that the ratio of ammonium polyphosphate, melamine and pentaerythritol as well as their content in the intumescent system is a factor determining the limit of the fire resistance of steel constructions, which a fire protective coating can ensure. Intumescent coatings with an ammonium polyphosphate:melamine:pentaerythritol ratio of 2:1:1 were shown to be more effective ones to provide the fire resistance of a steel construction during 30 minutes (R30). In turn, the use of the above ratio of 3.5:1:1.5 can provide the limit of the fire resistance of steel construction during 60 minutes (R60). The mixture of melamine and dicyandiamide in the intumescent system causes a synergistic effect, which leads to a non-additive increase in the fire protective efficiency of the coating. The results of this study have been confirmed by full-scale fire tests; they may be used to develop effective means of fire protection of steel constructions.