Polystyrene Foams as Core Materials Used in Vacuum Insulation Panel

Abstract

This work examines the foam density, average cell sizes, and cell structure of four polystyrene (PS) blended with calcium carbonate (CaCO3) or low density polyethylene (LDPE) at various ratios. The PS/CaCO3 and PS/LDPE are foamed by carbon dioxide (CO2) under supercritical conditions. CaCO3 and LDPE can strongly influence the foam density, average cell sizes, and cell structure of PS foams. Based on the result of PS/CaCO3 foams and PS/LDPE foams, the thermal conductivity of large porous PS foams as core materials used in vacuum insulation panels (VIPs) is further studied. Large porous PS foams are produced by the mixture of CO2 and fluorocarbon or the mixture of CO2 and nitrogen (N2) as foaming agents. The content of open-cells in PS foams is affected by materials, foaming temperatures, and foaming agents. A higher content of open-cells in a porous PS foam can lead to a lower and more stable thermal conductivity of VIPs.