Smart polyurethane composites: Magnetic-field-sensitive crosslinked shape-memory polyurethane composites

Smart polymers synthesized from renewable sources are precious because of the environmental pressures of producing polymers from fossil fuels. This study develops a new formulation of polyurethane (PU) from partly renewable resources. PU composites were prepared from castor oil (CO), polyethylene glycol (PEG3000), and hexamethylene diisocyanate (HDI). CO was used as both polyol and crosslinker. Butanediol and/or low molecular weight polyethylene glycol (PEG300) were added to the reaction medium as a chain extender. As a magnetic particle, natural magnetite or carbonyl iron was used in various amounts (0–10%). Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscope (SEM), optical microscope, and goniometer were used to characterize all composites and pure PU. A bending test was applied to investigate the shape fixity and shape recovery ratios of the samples. A range of hydrophilic/hydrophobic PU composites (water contact angle is between 56–87°) having various melting and glass transition temperatures were successfully prepared. A PU composite having a good shape recovery ratio (R_r = 96.1%) in a magnetic field was prepared using 10% magnetite. The PU composites were also thermosensitive.