Novel flexible polyurethane (PU)composite films containing nano-barium hexaferrite (BaF) and nano-barium titanate (BT) have been synthesized and characterized. ThePU nanocomposites were synthesized from fullerenol and prepolymer of hexamethylene diisocyante and polytetramethylene glycol by adding 13% each of BaF (high permeability) and BT (high permittivity). The incorporation of the nanopowders was confirmed by X-ray diffraction (XRD), transmission electron microscopy, and energy dispersive X-ray diffraction (EDX). Study of thermal properties bythermogravimetric analysisand dynamic mechanical analysis revealed enhanced thermal stability of the nanocomposites. Study of mechanical properties showed that the tensile strength had increased remarkably in the nanocomposites. The electromagnetic-absorbing properties were studied by measuring the complex permeability and permittivity in the frequency range of 8.2 to 12.4 GHz. The good reflection loss of the nanocomposites at such low filler content suggests its potential applicability as a radar absorber. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013