Effects of pore structure and gas phase on thermal conductivity of glass foams

Glass foams are an interesting material with various applications such as lightweight filling in road embankments and insulation material. For thermal insulation, the thermal conductivity is a crucial property. In general, thermal conductivity decreases with decreasing density, thus a simple way to improve the insulation value is to decrease the density. However, at low density some characteristics such as the cellular structure and the gas composition become important. The pore structure is important, as the heat transfer through the solid phase around one big pore is faster than between many small pores due to the tortuosity factor. The influence of gas composition becomes more pronounced with decreasing density due to a higher relative contribution of gaseous conductivity to overall thermal conductivity. Therefore, it is essential to generate closed pores in order to entrap a low conducting gas, such as CO2 rather than O2. In this presentation, we illustrate and discuss the effect of the pore structure and the gas composition on the thermal conductivity of glass foams.