Influence of intercalated modified hydrotalcite on the ultraviolet resistance of intumescent fire-retardant coatings

To better understand the influence of intercalated modified hydrotalcite on the ultraviolet resistance of intumescent fire-retardant coatings on wooden structures, this study is dedicated to exploring the flame-retardant properties of intumescent fire-retardant coatings with different mass fractions of hydrotalcite or intercalated modified hydrotalcite after ultraviolet exposure of different durations. The analysis focused on the performance and mechanisms of intercalated modified hydrotalcite.

Experimental specimens were prepared, including a control specimen (#0), five groups of fire-retardant coating specimens containing different proportions of hydrotalcite, and five groups containing different proportions of UV326-intercalated modified hydrotalcite. The specimens were subjected to ultraviolet (UV) irradiation for different durations. Their properties were analyzed using cone calorimeter, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR). Key fire-related parameters, such as ignition time, heat release rate, total heat release, effective heat of combustion, and total smoke release, were studied to assess performance differences.

Cone calorimeter tests revealed a significant improvement in the flame-retardant and UV-resistant properties of specimens containing hydrotalcite or intercalated modified hydrotalcite compared to the control group (#0). When the additive ratio was 2.7%, the aging rate decreased from 86% (#0) to 48% (hydrotalcite specimens) and 45% (intercalated modified hydrotalcite specimens), respectively. SEM analysis of the aged UV#3 (with 2.7% intercalated layered hydrotalcite) specimen, along with its expanded char layer, showed that intercalation modification effectively minimized hydrotalcite agglomeration in the coating. During the early stages of the UV aging process, the expanded char layer exhibited excellent performance, with a dense and thick structure, numerous pores, and a well-defined honeycomb-like pattern. With the extension of UV irradiation time, however, the char layer became increasingly fragmented and irregular. After 15 days, the control specimen (#0) was nearly incapable of forming a complete expanded layer. FTIR analysis indicated that UV aging treatment caused the decomposition of ammonium polyphosphate and polyacrylate resin in the flame-retardant system. The UV resistance of the intumescent fire-retardant coating with intercalated modified hydrotalcite was significantly enhanced. The inclusion of intercalated modified hydrotalcite caused the appearance of the C—N—C absorption peak, indicating the formation of a cross-linked structure between the amino groups in hydrotalcite and pentaerythritol.

This study underscores the importance of optimizing the formulation and application of fire-retardant coatings to effectively reduce the fire risk of wooden structures. Properly designed coatings can slow the flame spread and control local temperatures, but inappropriate coating choices or application strategies may lead to risks such as UV aging and uneven fire protection. These findings provide important technical insights for developing fire safety measures, highlighting the need to tailor fire-retardant coating strategies to wooden structures. This study offers valuable scientific evidence for improving fire safety management in wooden structures and holds practical relevance for improving the design and application of fire-retardant coatings.