Ethylene-bridged polysilsesquioxane/hollow silica particle hybrid film for thermal insulation material

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.