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-Si-29, NMR-B-11 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 degrees 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.