ABSTRACT
In this chapter, the effects of long-term storage in a commercial polyurethane shape-memory foam are investigated experimentally. The foams are pre-compressed above their glass transition temperature (Tg) to 80% and 93.4% strains, respectively, and then cooled back to room temperature. After various periods of cold hibernation, which are up to two months, the foams are heated up at fixed length or against prescribed different constant loads. The findings are twofold out of this study. First, the maximum stress that the foam could exert at fixed length depends largely on the amount of pre-strain applied during compression. Secondly, the expansion rates of 380% and 1273% from the hibernated size against a 1 N load (with pre-compression by 80% and 93.4%, respectively) are achievable. However, upon further increases in the applied load, the expansion is dramatically reduced. It appears that the polyurethane foam tested here is able to retain its excellent shape-memory properties even after being stored in a compacted state for up to two months.
