Characterization of high-temperature paints for infrared thermography in fire research

Infrared temperature measurements are common in fire research and adjacent fields to provide spatially-resolved temperature distributions on surfaces. To obtain accurate temperature values from these instruments, a well-characterized emissive surface is desired to minimize error in the calculated values. In fire applications, the robustness of the surface coating is also an important consideration. To this end, surfaces to be measured with infrared thermal cameras are commonly coated with a high-emissivity coating to reduce uncertainty in measurements. Here, the optical properties and thermal stability of a set of commercially available paints were characterized to assess their suitability for future applications and to provide a reference dataset for researchers. The thermal stability of the paints was assessed using thermogravimetry to measure degradation at elevated temperatures. Emissivity was determined spectrally at room temperature and as a band-averaged value as a function of temperature for long-wave infrared thermography applications. Differences were revealed in these tests, indicating a need to carefully select coatings based on the application, giving consideration to the exposure temperature, optical-sensing band, and dynamic emissivity input for temperature-varying environments. Properties collected were verified against a bench-scale experiment with flame exposure, demonstrating the accuracy and usefulness of infrared thermography in fire research applications.