Thermal conductivity of polyvinylpolymethylsiloxane aerogels with high specific surface area

The traditional SiO₂ aerogels are difficult to apply in the fields of energy storage and heat insulation due to their poor mechanical properties. In order to deal with this issue, the polyvinylpolymethylsiloxane aerogel (PVPMSA) materials with fine mechanical flexibility and excellent thermal insulation properties are suitable substitutions. In this paper, the double cross-linking organic-inorganic hybrid PVPMSAs were prepared through the processes of free radical polymerization and hydrolytic polycondensation. The internal silica network reinforced with aliphatic hydrocarbons has significantly improved the mechanical properties and acquired a high specific surface area, reaching up to 1218 m² g^-1. Furthermore, the thermal conductivity of monolithic PVPMSAs has been investigated by changing the density and environmental conditions. Results show that PVPMSAs at 25 °C in 5 Pa have a thermal conductivity as low as 14.69 mW m^-1 K^-1, and the solid thermal conductivity shows a flat growth with the increase of density. Meanwhile, the nanosize pores could significantly inhibit the heat transfer of gas. As for the radiative thermal conductivity, it is greatly affected by temperature. All these results obtained from this paper would help us to design thermal insulators reasonably.