Determination of the impact of environmental temperature on the thermal conductivity of polyisocyanurate (PIR) foam products

Polyisocyanurate (PIR) foam is a thermal insulation material increasingly used in construction and industry, with significantly lower thermal conductivity than others due to its fine structure and low conductivity blowing gases. The results of previous studies have shown that the thermal conductivity of PIR can increase due to exchange of the blowing gas with environmental gases during the operation, and when the material enters low temperature environments, where blowing gas condensation occurs. However, the conditions contributing to thermal conductivity increase of PIR haven't been sufficiently investigated, therefore detailed studies of thermal properties of PIR products were performed. Aging procedures with differently prepared PIR samples were performed in a climatic chamber, the thermal conductivities were measured by the heat flow meter and by Hot-box methods. The largest increase in thermal conductivity (up to 15%) was determined for samples stored at high temperatures (up to +70 degrees C), the changes in thermal conductivity are smaller for samples with diffusion-tight facings and higher - for thin and cut from the core of product samples. The aging at negative temperature has no effect on the thermal conductivity, however, the thermal conductivity of material at a mean -20 degrees C temperature increased by up to 20% compared to standard thermal conductivity. It was noticed that determined changes for the tested material are significantly smaller than those described in previous studies, so the results of this study will contribute to a wider use of PIR products and more accurate assessment of the energy performance of buildings.