Studies on the effect of atmospheric oxygen content on the thermal resistance of intumescent, fire-retardant coatings

Studies are conducted to measure the rate of thermal degradation and the thermal resistance of three intumescent fire-retardant coatings under atmospheres of varying oxygen content. The degradation trials are conducted using thermal gravimetric analysis and differential thermal analysis in an atmosphere of nitrogen or air. It has been found that a low oxygen content in the atmosphere significantly affects the rate of degradation of the char material at temperatures greater than 540°C. The global kinetics of the thermal degradation is modeled using three or four first-order parallel reactions. The degradation of char is modeled using the method of invariant kinetic parameters. The derived kinetic parameters are reported. The thermal resistance of the materials coated on steel plates is determined using a cone calorimeter with controlled oxygen content in the atmosphere. It has been found that the thermal resistance of two of the coatings has been strongly influenced by the oxygen content of the atmosphere; hence, this factor may be of importance when predicting the performance of intumescent materials in real fire scenarios.