EVALUATION OF THE THERMAL STABILITY OF STYRENE-ACRYLIC INTUMESCENT COATINGS

This study investigates the thermal stability and intumescent performance of fire-protective polymeric coatings based on a styrene-acrylic dispersion matrix, incorporating ammonium polyphosphate (APP), pentaerythritol (PE), and aluminum hydroxide (Al(OH)₃). These coatings are designed to enhance fire resistance of steel structures by forming an insulating char layer when exposed to high temperatures. The research applies thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) to assess thermal degradation behavior, identify decomposition stages, and quantify residual char formation. Experimental findings reveal that individual components exhibit different degradation profiles: APP decomposes with the release of phosphoric acids acting as acid catalysts; PE serves as a carbon source undergoing esterification and subsequent carbonization; Al(OH)₃ decomposes endothermically, releasing water vapor and forming aluminum oxide, which contributes to thermal insulation and structural integrity of the char. The combination of these ingredients in a single system demonstrates a synergistic effect, providing improved thermal stability, reduced mass loss, and higher residual mass at temperatures up to 800 °C. The intumescent mechanism proceeds through several stages, including dehydration, esterification, carbonization, gas release, and foam formation. The thermal barrier created by the expanded char layer significantly delays heat transfer to the substrate, thereby increasing the fire resistance time of steel components. The DTG curves clearly indicate enhanced performance of the composite system compared to coatings containing individual additives. The study concludes that optimized formulations with APP, PE, and Al(OH)₃ can deliver effective fire protection by ensuring controlled thermal decomposition, robust char formation, and improved thermal insulation. These results support further development of high-performance, eco-friendly intumescent coatings for fireproofing applications in civil and industrial engineering.