Effect of steaming on shape memory polyurethane fibers with various hard segment contents

Abstract

To illustrate the effect of post-treatment high-pressure steaming and hard segment content on shape memory polyurethane (SMPU) fiber, a series of shape memory polyurethane having various hard segment contents was synthesized with the pre-polymerization method, spun with a wet spinning process and treated with high pressure saturated water vapor. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle x-ray diffraction (WAXD), mechanical testing and cyclic tensile testing were conducted to investigate the particular thermal/mechanical properties, crystallization of hard segments and shape memory properties of SMPU fibers. In addition, in the light of a comparison between the original and the treated SMPU fiber, the effect of steaming post-treatment in SMPU fibers with various hard segment contents was illustrated. The steaming treatment gives rise to a higher elongation ratio at break, lower tenacity and initial modulus. Hard segment crystallization can be induced, especially in fiber with higher hard segment content after treatment. The glass transition temperature of the soft segment of SMPU fibers was decreased after steaming and the trends are most likely significant in high hard segment content specimens. Steaming with high pressure saturated water vapor can eliminate the thermal shrinkage and provide dimensional stability to the original SMPU fibers. The recoverability remains well in all treated specimens, but the fixity ability decreases with the decrease of hard segment content.

Properties of shape memory polyurethane used as a low-temperature thermoplastic biomedical orthotic material: influence of hard segment content

“…Also, they do not flow at the temperature because of them. According to the literature [14,31,35], the stable crystallized hard segment phase of shape memory polyurethanes will not be destroyed until it is heated to above a minimum of 170 • C. Now no proper standard are available for these tests. Therefore, in this article, according to practical application, they were roughly tested using to the more immediate method.…”

“…The frozen phase acting as the physical cross-link capable of storing elastic energy is responsible for memorizing the permanent shape. The thermally reversible phase which is a crystalline state or a glass state serving as a "switch" enables the fixing and unfixing of a temporary shape [13,14]. When the shape memory polyurethane is heated to the switching transition temperature (melting or glass transition temperature of soft segment phase), the modulus has a great drop because of melting transition or glass transition of the reversible phase.…”

Biological Evaluations of a Smart Shape Memory Fabric

“…It was dehydrated with 4 Å molecular sieves for two days prior to being used. The polyurethane was synthesized by the pre-polymerization method using PBA-600 (Mn) (Aldrich Chemical Company, USA) as the soft segment, while 4,4'-methylenebis(phenylisocyanate) (MDI) and 1,4-butanediol (BDO) as the hard segment [28,36]. Prepolymerization was conducted by terminating P with excess MDI at both ends in a 500 ml four-necked flask equipped with a mechanical stirrer, purge gas (nitrogen) inlet, thermometer, and condenser.…”

“…This is mainly due to the difficulties of synthesizing high quality shape memory polymer for fiber spinning and the spinning technique of shape memory polymers. Recently, our research team developed shape memory fibers through wet spinning and melt spinning methods based on several years of work [27][28][29][30][31]. In comparison with their bulk counterpart, shape memory fibers may have outstanding mechanical properties and shape recovery force because of molecular orientation.…”

A smart hollow filament with thermal sensitive internal diameter

“…This may be due to the fact that the hard segment content in the TSHF is relatively low, and consequently, no well-ordered hard segment phase forms. According to previous studies, no crystallized structure of hard segment will form unless the hard segment content is very high such as above 50 wt % 25,47 As at an ambient temperature, the soft-segment phase is partially crystallized, and the TSHF is not completely elastic as those in elastic polyurethane fibers. 48,49 …”