Preparation and thermal stability of UV-cured epoxy-based coatings modified with octamercaptopropyl POSS

•EA/POSS hybrid films were prepared via thiol-ene photopolymerization.•An double effect of OMP-POSS on the thermal stability of hybrid films.•Reduction of the flammability of EA/POSS nanocomposites.

UV-curable epoxy acrylate (EA) modified with octamercaptopropyl polyhedral oligomeric silsesquioxane (OMP-POSS) was prepared via thiol-ene photopolymerization. The study of microscale combustion indicated that EA/POSS nanocomposite displayed both the slower heat release rate and lower total heat release. The result of thermal degradation of the cured films showed that OMP-POSS had a double effect on the thermal stability of EA due to its structure containing both the relatively weak mercapto moieties and the POSS core resistant to heat shock, the derivation from the former (thioether linkages) leading to the early decomposition of the nanocomposites whereas the latter providing the well protective effects on some moieties of EA like aromatic groups and on the carbonaceous char. The analysis for the residues of EA2 with 20 wt% OMP-POSS exhibited that POSS can well protect the carbonaceous char from thermal-oxidative degradation at 600 °C, but do not work at 800 °C.