Vacuum insulation properties of phenolic foam

Characteristic properties of phenolic foam as the interstitial material of a vacuum insulation panel are investigated experimentally. For the measurement of effective thermal conductivity, a vacuum guarded hot plate (VGHP) apparatus is used and the conductivity is measured at various vacuum levels. Radiative properties are found using a Fourier transform infrared spectroscopy (FT-IR) device. Solid conductivity is estimated using the porosity of the foam. Effective thermal conductivity at high level of vacuum is measured to be 5 mW/m K which is sum of solid conductivity (2.56 mW/m K) and radiative conductivity (2.44 mW/m K) with 5% of measurement uncertainty. The pore size of the foam is estimated to be 260 μm using rarefied gas conduction theory. This ensures insulation performance of phenolic foam up to about 10−3 atm. Other practical characteristics of phenolic foam as the VIP core material are also discussed.