Shape Fixity and Shape Recoverability in a Film of Shape Memory Polymers of Polyurethane Series.

Abstract

The shape fixity and the shape recoverability of a shape memory polymer film of polyurethane series were investigated by means of thermomechanical cycling tests. The main results are summarized as follows. (1) In the case of small maximum strain, the deformation properties do not vary under cyclic loading. (2) The shape fixity of the material does not vary under cyclic deformation. (3) In the case of large maximum strain, the shape recovery temperature rises and the irrecoverable strain increases under cyclic deformation. Mechanical training before practical use is effective in order to obtain stable shape recoverability. (4) Thermal stress resulting from cooling under constant maximum strain appears in the case of small strain. (5) The deformation properties of the materials with different glass transition temperatures show almost the same tendency.