Effect of Envelope Films on Thermal Properties of Vacuum Insulation Panels with Glass Fiber

The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the materials were measured by the heat flow meter. The microstructure of the envelope film was observed by scanning electron microscopy. The porosity ratio and largest pore size diameters of the core materials are 92.27% and 20 mu m, respectively. The thermal conductivity of the VIP is about 8-10 times higher than that of the core materials. The thickness of type land IT envelope films are 45 mu m and 400 mu m, respectively. The thermal conductivities of the type I and type II envelope films are 0.11 W/(m.K) and 0.69W/(m.K), respectively. The thermal conductivity of the VIP with type II envelope is higher than that of the VIP with type I envelope, which is attributed to the different structures and thickness of the envelope film.