An Insight into Insulation Performance for HFO Blown PIR Systems

摘要

Rigid foam used as building materials is required both incombustibility and heat insulation properties for fire safety and energy efficiency. Polyisocyanurate (PIR) foam shows excellent flame retardancy compared with polyurethane (PU) foam. On the other hand it is difficult to maintain heat insulating performance for a long time. Therefore in this study, we measured aging variation of thermal conductivity on laminate board of PIR foam using Hydrofluoro-olefin (HFO) as a blowing agent which has high insulation performance and is environmental friendly and also investigated the aging variation mechanism. It was confirmed that there were three stages in aging variation of thermal conductivity on PIR board. In an initial stage (Stage 1), thermal conductivity increased rapidly. In middle stage (Stage 2), the aging variation of thermal conductivity was very slight. And in later stage (Stage 3), the thermal conductivity started to increase again. Furthermore, the cause of the aging variation at each stage was analyzed in detail. As the result, the aging variation of thermal conductivity was caused by three factors, which were carbon dioxide generation after demolding, moisture absorption and diffusion of gases. These factors were correlated with amount of NCO groups remaining in the resin, polyol structures and cell sizes of the foams. Finally, we developed a novel isocyanate, which was effective for cell size control and reduction of residual NCO group content. The optimized PIR laminate board maintained the thermal insulation property about 95% for one year after production.