Electrospun nonwovens of shape-memory polyurethane block copolymers

Synthesized shape-memory polyurethane (PU) block copolymers were used to prepare electrospun nonwovens via electrospinning. PU solutions were prepared with a mixed solvent of N,N-dimethylformamide and tetrahydrofuran. The electrospun PU nonwovens were prepared with hard-segment concentrations of 40 and 50 wt %. The morphology of the electrospun fibers was investigated with scanning electron microscopy. The average diameter of low-viscosity (ca. 130-180 cPs) electrospun fibers was about 800 nm, and the morphology of the electrospun nonwovens was beaded-on fibers. In contrast, the average diameter of high-viscosity (ca. 530-570 cPs) electrospun fibers was about 1300 nm. In an investigation of the mechanical properties of the electrospun PU nonwovens, it was found that the tensile strength increased as the hard-segment concentration increased within a similar range of viscosities. Also, the tensile strength of the electrospun PU nonwovens in the machine direction was higher than that in the transverse direction because of a difference in the velocities of the drum collectors. The electrospun PU nonwovens with hard-segment concentrations of 40 and 50 wt % were found to have a shape recovery of more than 80%. (C) 2005 Wiley Periodicals, Inc.