Influence of processing conditions on the microstructure and properties of shape memory polyurethane membranes

Solution-cast films of shape memory polyurethane are investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, tensile properties, water vapor permeability, and shape memory effect tests. Samples cast at higher temperatures contain more hard segments in the crystalline state and better water vapor permeability than samples cast at lower temperatures. The change in water vapor permeability of shape memory polyurethane films with respect to temperature follows an S-shaped curve, and increases abruptly at T-s, the shape memory temperature of the soft segment. The higher the modulus ratio at two specified temperatures before and after T-s, the better the shape memory behavior of shape memory polyurethane.