Investigation into Stress Recovery Behavior of Shape Memory Polyurethane Fiber

In this work, the stress recovery behavior of shape memory polyurethane (SMPU) fiber was investigated. The as-spun SMPU fibers were subjected to various programing-recovery conditions. It was observed that recovering at 100 degrees C generated higher recovery stress than recovering at 150 degrees C. It was also found that, while hot-drawn programed fiber has higher recovery stress than cold-drawn programed fiber if recovered at 100 degrees C, cold-drawn programed fiber has higher stabilized recovery stress than hot-drawn programed counterpart when recovered at 150 degrees C. A morphological model was proposed based on the results from differential scanning calorimetry, Fourier transform infrared spectrometry, and X-ray diffraction to understand the physics behind the different stress recovery behaviors. It is found that SMPU experiences different phase transitions and phase separations under different programing and stress recovery conditions. It is concluded that the two sequential phase separations taking place at 100 and 150 degrees C are primarily responsible for the differences in the stress recovery behavior. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1429-1440