# Complementary Techniques of Thermal Analysis as a Tool for Studying the Properties and Effectiveness of Intumescent Coatings Deposited on Wood

## TL;DR

This paper explores how thermal analysis techniques can assess fire-retardant coatings on wood, identifying the most effective coating and the gases it releases during fire exposure.

## Contribution

The study demonstrates the use of advanced thermal analysis methods to evaluate and compare the performance of intumescent coatings on wood.

## Key findings

- Coating No. 3 provided the best fire protection, initiating protection at lower temperatures and reducing combustion enthalpy by 50%.
- TGA-IST16-GC-MS outperformed TGA-MS in identifying complex gaseous products from coating degradation.
- DSC-microscopy allowed direct observation of coating expansion and degradation during thermal exposure.

## Abstract

Fire-retardant intumescent coatings offer an effective means of enhancing the fire resistance of combustible substrates such as wood. These coatings have a complex chemical composition and, when exposed to temperatures above 200 °C, undergo an intumescent reaction accompanied by the release of non-flammable gases, forming an expanded, charred layer with low thermal conductivity. This provides thermal insulation and acts as a physical barrier against heat, oxygen, and flammable volatiles. In this study, the applicability of several thermoanalytical techniques for evaluating the performance of three different intumescent coatings applied to spruce wood was investigated. Simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that coating No. 3 was the most efficient, initiating substrate protection at the lowest temperature and reducing the combustion enthalpy by approximately 50% compared to uncoated wood. DSC-microscopy visualization enabled direct observation of the intumescent expansion, degradation of the carbonized protective layer, and delayed thermal decomposition of coated wood. Furthermore, a comparison between TGA-MS and TGA-IST16-GC-MS demonstrated the superiority of chromatographic separation for identifying evolved gaseous products. While TGA-MS is effective for detecting small gaseous species (e.g., H2O, CO2, formaldehyde), TGA-IST16-GC-MS enables the deconvolution of many degradation products evolving simultaneously, allowing for distinction between flame-retardant-related species, polymer backbone fragments, nitrogen-rich heterocycles, and small oxygenated molecules in the most effective coating.