Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Abstract

Summary Aerogels are one of the most promising nano‐dimension open‐cell foams with considerably varied characteristics such as high porosity, super large specific surface area, low density, and super low thermal conductivity. Aerogel's high porosity and microstructure consisting of micro‐ and nanoparticles as well as pores in nanometer dimension are the origin of distinctive properties. However, the main challenge of aerogels is their low density (0.05−0.50 gcm3), which leads to equal thermal diffusion (normalα×10−7) compared with general thermal insulators. To minimize aerogel thermal diffusion and to enhance thermal insulation, replacing some aerogel colloids with phase‐change material nanocapsules (NPCMs) (while aerogel IUPAC definition and at least porosity of 80% is preserved) is proposed in this work. While NPCMs undergo a physical change during phase transfer, temperature becomes persistent, and as a consequence, specific heat capacity (Cp) getting close to an infinite number and thermal diffusion (normalα=knormalρCp) will tend to very low values. Results have demonstrated that by only applying 4.5 wt.% of paraffin wax core /polyurethane shell (PW/PU) NPCMs instead of some novolac aerogel colloids, aerogel has experienced temperature decrement as well as stability. During NPCMs' melting process, thermal diffusivity has reached 2.5×10−12 and temperature increment delay rate has become 40%.