Abstract: Thermal conductivities are tested periodically on two different density rigid polyurethane foams blown with cyclopentane. By cutting products into thin slices and after aging 165 days in room temperature, the rising curves display two different ascending steps during test period and they are proved to be true of logarithmic relationship by function fitting. Finally the values obtained from logarithmic function need to be corrected by subtracting surface cell size destroyed in cutting. The results indicate that thermal conductivity of 50mm thick product will not exceed 0.029 W(m•K)-1 after using 25 years in practice.

Key words: Polyurethane, foam aging, thermal conductivity, prediction