Shape memory characterization of poly(ε-caprolactone) (PCL)/polyurethane (PU) in combined torsion-tension loading with potential applications in cardiovascular stent

Shape Memory Polymers (SMPs) were proved to be employable for biomedical application but still their performance in progress. In this study, the combined torsion and tension loading of polyurethane/poly(ε-caprolactone) (PU/PCL) blend as SMP were investigated experimentally. In addition to the viscoelastic response, the stress and shape recovery are studied. Samples are characterized by DSC, DMTA and tensile test to accomplish higher performance. Results showed that samples prepared by solution mixing method has higher storage modulus and loss modulus respect to samples blended by melt mixing method. In order to extend the usage, the pre-torsion and pre-stretch strains were imposed on PU/PCL strips and stress recovery and shape recovery were reported. The results show that higher stress recovery response demands higher pre-stretched and lower deformation temperature. Maximum stress recovery occurred in deformation temperatures of 30 °C and 40 °C. Also, angle recovery behavior in low pre-torsion was dependent on pre-stretch while tension recovery was slightly affected by pre-torsion in the angle of 540° and 720°. Among all parameters, the heating rate has the greatest effect in reducing recovery finished temperature. These new findings can be used to develop new SMP structures in the combined loading condition and better performance in biomedical scaffold applications.