Investigation into stress recovery behavior of shape memory polyurethane fiber

Abstract

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 °C generated higher recovery stress than recovering at 150 °C. It was also found that, while hot‐drawn programed fiber has higher recovery stress than cold‐drawn programed fiber if recovered at 100 °C, cold‐drawn programed fiber has higher stabilized recovery stress than hot‐drawn programed counterpart when recovered at 150 °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 °C are primarily responsible for the differences in the stress recovery behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1429–1440

Cold, warm, and hot programming of shape memory polymers

“…Second, the stabilized recovery stress of cold‐programmed SMPs, with the same fixed strain, may be higher, equal to, or lower than that by HP, depending on the prestrain level, recovery condition, and SMP composition and morphology. This is why different results have been reported in the literature . In addition, CP may cause damage and irreversible deformation, which may lower the stiffness of the specimen and the stabilized recovery stress.…”

Temperature and rate dependent thermomechanical modeling of shape memory polymers with physics based phase evolution law

“…Unlike the free strain recovery test, where the recovery strain normally shows a plateau at the end of the test, the stress recovery test is more complicated. In some cases, the recovery stress follows a similar pattern to strain recovery, i.e., gradually approaches to a plateau (Ivens et al, 2011;Yang and Li, 2014a). In some other cases, however, "stress undershoot" (Arrieta et al, 2014;Liu et al, 2006;Tobushi et al, 2001;Véchambre et al, 2011) and "stress overshoot" (Castro et al, 2010;Li and Nettles, 2010;Li and Uppu, 2010;Qi et al, 2008) are observed.…”

Self-healing properties of layer-by-layer assembled multilayers

“…Shape memory systems are another important area of self‐healing composites . Modeling of shape memory polymer response and shape recovery loss was recently published . A variety of composite polymer materials with shape memory effect were designed in Mather's group .…”