Heat-insulating materials with high-temperature resistance through binding hollow glass microspheres with vinyl-functionalized polyborosiloxane

In this study, a kind of novel heat-insulating material composed by the vinyl-functionalized polyborosiloxane (BSiO) and hollow glass microspheres (HGM) was successfully prepared. Under solvent-free condition, the BSiO was synthesized by reacting triethoxyvinylsilane (VTEOS) and boric acid by one-pot method and characterized by GPC, FT-IR, NMR-²⁹Si, NMR-¹¹B and TGA analysis. The results indicated that the monomer feed ratio of the reactant made a great difference on the molecular structure and thermal stability of the BSiO and the BSiO-2 showed the best thermal stability when the feeding ratio of VTEOS and BA was 1.5. Moreover, the ceramic conversion analysis indicated that the BSiO-2 tended to form the inorganic SiBOC nanocomposite. Properties, such as the microstructure, density, linear shrinkage, compressive strength and thermal conductivity, burning behavior and flame retardancy of the BSiO-2/HGM composites after different heat treatment, were studied. The SEM results showed that the BSiO-2 could effectively wet the surface of HGM and the HGM was glued together firmly. With the increase in heat treatment temperature, the density and thermal conductivity of BSiO-2/HGM composites reached the minimum value at 600 °C, while the compressive strength reached the maximum value. The result of flame retardancy study showed that the composites possessed high LOI value (> 50%) and hardly any smoke could be observed during the burning process. This indicated that the BSiO-2/HGM composites possessed excellent flame-retardant property and fire safety. This paper will provide ideas for the design and preparation of heat-insulating materials with polyborosiloxane as heat-resistant binder.