Ethylene-bridged polysilsesquioxane (EBPSQ) was prepared by the sol-gel reaction of bis(triethoxysilyl)ethane. The whitish slurry was prepared by mixing EBPSQ and hollow silica particles (HSPs) with a median diameter of 18-65 μm at 80 °C, and it formed a hybrid film by heating at 80 and 120 °C for 1 h at each temperature, then at 200 °C for 20 min. The surface temperatures of EBPSQ films containing 10 wt% and 20 wt% of HSPs (90.2 °C-90.5 °C) were lower than those of EBPSQ films (93.6 °C), when the films on the duralumin plate were heated at 100 °C for 10 min from the bottom of the duralumin plate. The thermal conductivity/heat flux (k/q) obtained from the temperature difference between the surface temperature and bottom temperature of the films and the film thickness also decreased with adding the HSPs. EBPSQ film without HSPs exhibited T 5 d of 258 °C and T 10 d of 275 °C. However, EBPSQ film containing 20 wt% of HSPs exhibited high thermal stability, and T 5 d and T 10 d were 299 °C and 315 °C, respectively. Interestingly, T 5 d and T 10 d of the hybrid films increased with an increase in the number of HSPs. Overall, it was shown that HSPs could improve the thermal insulation properties and thermal stability.
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