Photo-aging deterioration of hybrid intumescent flame retarding coatings simultaneously modified by silicon aerogel, β-cyclodextrin, and nano-ZnO

Photo-aging has been manifested as the main threat to the service performance of organic coatings, but the deterioration of intumescent flame retarding coatings (IFRC) is scarcely reported. Therefore, the finish IFRC is benignly designed by simultaneously incorporating silicon aerogel, beta-cyclodextrin, and nano-ZnO, its deterioration mechanism under photo-aging (composed of xenon lamp radiation and water spraying) is quantitatively investigated. The results show that the photo-aging facilitates the declined flame retardancy, as measured by the rising fire growth index from 1.07 to 2.43 kW m(-2).s(-1) and the reduced fire performance index from 0.493 to 0.196 s.m(2).kW(-1) with the flame retardancy index of 0.18 for S-30d, as well as the diminished smoke suppression. Because the cleavage of C=N-bonding occurs for the IFRC subjected to photo-aging, presenting the serious yellowing of the IFRC surface with enhanced hydrophilicity. Meanwhile, the light-humidity cycles of photo-aging lead to the transformation from glassy residue to crystalline SiP2O7 during firing, presenting the disorder and fluffy char for S-30d. Thirdly, the photo-aging makes the pyrolysis E-alpha of 370 similar to 320 degrees C drop from 177.9 to 120.2 kJ.mol(-1) by the modified Coats-Redfern integral method. It probes the photo-aging deterioration mechanism of organic-inorganic hybrid IFRCs.

Automated summary

This study found that photo-aging accelerates the deterioration of intumescent flame retarding coatings by affecting their flame retardancy, fire performance, smoke suppression, and surface yellowing; it also causes the formation of disordered and fluffy char during combustion. Additionally, photo-aging lowers the pyrolysis activation energy of the coatings, and the incorporation of materials such as silicon aerogel, beta-cyclodextrin, and nano-ZnO can improve the stability of the coatings to some extent.