The thermal transport properties of synthetic porous insulators have been measured as a function of temperature. Three samples—foam, closed-cell foam, and fibreglass—have been subjected to different temperatures at different pressures, with compressibility of the samples and the requirements of the technique (transient plane source) taken into account. These materials are used for insulation in temperature control of air-conditioned space and electric appliances, so they are useful in reducing energy losses. The three samples have thermal conductivity, λ, in the range 0.024-0.087 W m~(-1) K~(-1); heat capacity per unit volume, ρC_(p), in the range 0.04-0.14 MJ m~(-3) K~(-1); and thermal diffusivity, κ, in the range 0.512×10~(-6)-0.689×10~(-6) m~(2) s~(-1), with an experimental error not more than 2. Foam and fibreglass work successfully as good heat insulators in extreme conditions of pressure and temperature (maximum 414K for the foam, 373K for the closed-cell foam, and 400 K for the fibreglass). Under different conditions of temperature and pressure, foam as compared to closed-cell foam and fibreglass exhibits insignificant changes in thermal transport properties. Hence foam is the best choice, of the three samples used in the experiment, for thermal insulation under extreme conditions of temperature and pressure.
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