The mechanical-viscoelastic model and WLF relationship in shape memorized linear ether-type polyurethanes

A modified mechanical-viscoelastic model with two Maxwell models in parallel is proposed to describe the shape memory behavior of segmented polyurethanes (PUs). Based on the view of viscoelasticity, the influence of the fixed phase (hard segment) and the reversible phase (soft segment) on the shape memory effect is studied. The WLF equation is adopted to describe the relationship between the viscosity of the reversible phase and the temperature by using the selected reference temperature and the adjustable parameters. The parameters of the WLF equation are dependent on the M.W. of the soft segment of PUs. Finally, the model could properly describe the mechanism of shape memory behavior of segmented PUs. Moreover, the change of the recoverable curve of the deformed model is similar to that of experimental datapoints.