Environmentally friendly novel conductive, magnetic films derived from waterborne polyurethane (WPU) and Fe3O4 were successfully synthesized by in situ polymerization technique. Fe3O4 nanoparticles prepared via a solvothermal method were covalently functionalized with 3-(triethoxysilyl) propyl isocyanate (IPTS) to improve dispersion and compatibility with the WPU matrix. Different from previous work, the modified Fe3O4 nanoparticles (Fe3O4-IPTS) can chemically bond with WPU chains and form stable nanocomposite latexes before IN-curing, which benefited the improvement in some performances of WPU. The results revealed that the functionalization of Fe3O4 facilitated the dispersion of Fe3O4 as fillers in the WPU matrix and greatly improved the storage stability of the WPU/Fe3O4 nanocomposite latex (>3 months). Furthermore, the solvent resistance, mechanical properties, electrical conductivity, and magnetic properties of WPU were enhanced with incorporation of Fe3O4-IPTS. Importantly, the nanocomposites showed high electrical conductivity (8.43 x 10(-4)S/cm) and superior magnetic properties (14.22 emu/cm(3)) with a low Fe3O4-IPTS content of 8.0 wt.%, providing a promising route to prepare environmentally friendly WPU-based microwave absorption materials. (C) 2015 Elsevier B.V. All rights reserved.