Long-term thermal conductivity of aerogel-enhanced insulating materials under different laboratory aging conditions

Aerogel-enhanced materials are known to have significantly lower thermal conductivity than traditional insulating materials. However, given the lack of long-term experiences with aerogel-enhanced products, the consistency of their superior thermal performance under the effect of the various climatic aging processes is still unknown. This study describes the effects of accelerated aging processes in laboratory conditions over the thermal performance of aerogel-enhanced insulating materials. Several products including aerogel-enhanced plasters, blankets, and boards, were exposed to different climatic accelerated stresses, which exceeded typical use conditions. The tests included freeze-thaw cycles, elevated temperature, high humidity levels, and the exposure to cycles of high UV levels alternated to high temperature and moisture levels. The thermal properties of the products before, during, and after the accelerated aging periods were measured. The Peck model, Arrhenius equation, and Coffin-Manson relation were hence employed to correlate the accelerated aging results with the corresponding real service conditions. The paper discusses the acceleration factors of the aging tests and their calculation methods. The long-term performance of the products is quantified through the changes of their thermal conductivity measured over wide temperature ranges. The results show that for the different investigated materials, the increase in the thermal conductivity over the pristine conditions is typically below 10% for aging exposure corresponding to 20 years in typical conditions. Finally, this study suggests that despite some aging-driven degradation, the thermal conductivity of aerogel-enhanced materials after aging remains significantly lower than that of non-aged traditional insulating materials.