Shape Fixity and Shape Recovery in a Film of Shape Memory Polymer of Polyurethane Series

Abstract

The shape fixity and recovery in a film of shape memory polymer of polyurethane series were investigated by the thermomechanical cycling tests with loading at various temperatures. The results are summarized as follows: (1) Strain is recovered at temperatures in the vicinity of the glass transition temperature Tg for loading above Tg, but it is recovered at temperatures in the vicinity of the midpoint temperature of glass transition for loading below Tg. (2) The rate of strain fixity is 98% for loading above Tg, while it decreases with increasing cycles for loading below Tg. (3) The rate of strain recovery for loading above Tg is 98% except for the early cycles. (4) The thermomechanical properties of materials with different Tg are quite alike in spite of the difference in Tg.