Hyperbranched polyurethane/Fe3O4 thermosetting nanocomposites as shape memory materials

Nanocomposites of hyperbranched polyurethane were prepared by the in situ pre-polymerization technique with Fe3O4 nanoparticles. The synthesized Fe3O4 nanoparticles were characterized by the Fourier transform infrared spectroscopy and the X-ray diffraction study. The transmission electron microscopic study indicates the homogeneous distribution of Fe3O4 nanoparticles in the polymer matrix. The mechanical, thermal and shape memory behaviors of the nanocomposites were studied as a function of nanomaterial content. The glycidyl bisphenol-A based epoxy cured thermosetting nanocomposites exhibited significant improvement of tensile strength (5.7-18 MPa), scratch hardness (3.0-6.5 kg) and thermal stability (241-275 A degrees C) with the increase of the content of Fe3O4. The nanocomposites possess excellent shape fixity over the repeated cycles of test. They also showed good shape recovery under the application of microwave energy. The shape recovery speed found to increase with the increase of the loading of Fe3O4 in the nanocomposites. Thus, the prepared nanocomposites might be utilized as advanced shape memory materials in their potential fields.