Fire protection of ultraviolet-aged intumescent coatings containing polyhedral oligomeric silsesquioxanes

Intumescent coatings are alternatives for protecting substrates against fire and can be applied externally, being exposed to inclement weather, such as solar radiation, making it necessary to know the effect of this exposure on their protective properties. This study developed benzoxazine- and epoxy-based intumescent coatings containing different types of polyhedral oligomeric silsesquioxanes (POSS), to evaluate the influence of UV aging on fire resistance properties. The coatings were formulated, applied on metallic substrates, and exposed to UV aging. Coatings without exposure to aging were also evaluated. The coatings were characterized using burning tests, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, combustion microcalorimetry and visual analysis. The char layers were characterized using optical microscopy and scanning electron microscopy. FTIR results indicated absorption bands related to functional groups typical of degradation for each resin. The burning test revealed that aging exposure decreased the fire protection of all coatings. Coatings containing POSS with nonreactive groups showed better protective properties after UV aging when compared with the ones containing reactive groups.