Silica aerogel porosity and hydrophobicity enhance thermal insulation of coatings

Abstract

The high requirement for energy conservation boosts the development of aerogel used as an insulation material. However, the influence mechanism of their hydrophilicity on thermal insulation performance has not attracted much attention. In this work, high-performance waterborne thermal insulation coatings were obtained through adjusting the mass ratio of hydrophobic and hydrophilic silica aerogel. When their mass ratio reached 3:1, the coatings had the best comprehensive performance with the thermal conductivity of 0.075 W/(m·K), and the strengths of dry adhesion and wet adhesion of 1.63 and 0.82 MPa, respectively. The contact angle was 97.8°. Hydrophilic aerogels are easy to absorb water vapor and connect with each other, resulting in high thermal conductivity of the coating. The hydrophobic aerogel shows stereoscopic and even dispersion, which effectively prolongs the heat transfer pathway and thus reduces the thermal conductivity of the waterborne coating. This work presents a promising material design principle to create high-performance insulation materials.