Measurement of thermal conductivity of building insulation foams by modulated differential scanning calorimetry — Critical review & observations

The rise in energy prices, the need to conserve energy and the pressure to protect the environment promote the development of innovative eco-friendly thermal insulating foams for building applications. In this quest, a rapid and accurate method to measure the thermal conductivity of new foams is required during the research and product development stage. Temperature-modulated differential scanning calorimetry (MDSC) provides thermal conductivity values from heat capacity measurements on cylindrical samples less than about 20 mg in weight. This method is the basis of the ASTM E1952 standard method “Thermal Conductivity and Thermal Diffusivity by Modulated Differential Scanning Calorimetry”. In this work, the MDSC and the ASTM E1952 test methods are applied to thermal insulating foams used in construction applications. Measurements on polystyrene, polyurethane, and polyisocyanurate insulations demonstrate that MDSC possesses excellent repeatability, but its application through ASTM E 1952 provides inaccurate thermal conductivity values. Two sources of errors were identified, 1) the use of nitrogen as a purge gas, and 2) the use of an equation that inaccurately relates the measured heat capacity to thermal conductivity. Methods around these difficulties exist, but they remain untested with insulating foams.