Basic Deformation Properties of a Polyurethane-Series Shape Memory Polymer Film.

Abstract

The basic deformation properties of a polyurethane-series shape memory polymer film were investigated experimentally. The main results are summarized as follows. The modulus of elasticity below Tg is about 100 times larger than that above Tg. The loss tangent in the vicinity of Tg is about 0.6. In the case of cyclic deformation above Tg, yield stress decreases and irrecoverable strain increases with increasing number of cycles. The cyclic deformation properties vary significantly in the early cycles but vary only slightly afterwards. The strain obtained by loading at high temperature followed by unloading at low temperature is almost equal to the maximum strain. The residual strain does not vary under thermomechanical cycling, which indicates the shape fixity stability of the material under cyclic deformation. The rate of strain recovery by heating after several thermomechanical cycles is more than 95%.