Electromagnetic Field Absorbing Polypropylene Nanocomposites with Tuned Permittivity and Permeability by Nanoiron and Carbon Nanotubes

Highly efficient electromagnetic field absorption at gigahertz (GHz) was reported in the novel magnetic polymer nanocomposites (MPNCs) with in-situ synthesized Fe@Fe 2 O 3 core@shell nanoparticles (NPs) or their decorated multiwall carbon nanotubes (MWNTs) dispersed in the polypropylene (PP) matrix through a one-pot bottom-up method. PP grafted maleic anhydride (PP- g -MA) with different molecular weights served as surfactant to stabilize the in-situ-formed NPs and simultaneously as compatibilizer to enhance the bonding at the PP–filler interfaces. Because of the strong magnetization of the PP MPNCs filled with 20.0 wt % Fe@Fe 2 O 3 NPs stabilized by PP- g -MA ( M n = 800), a minimum reflection loss (RL) of −31.5 dB was observed at 18.0 GHz, and the frequency bandwidth with RL lower than −10.0 dB was 3.1 GHz (from 16.9 to 20.0 GHz) in the MPNC sample with a thickness of 5.5 mm. However, due to the lack of magnetic loss, only a weak RL of 4.3 dB was found at frequency of 16.8 GHz for the PP/PP- g -MA ( M n = 800)/1.0 wt % MWNTs nanocomposites sample with a thickness of 5.5 mm. When the PP MPNCs filled with Fe@Fe 2 O 3 NPs decorated MWNTs (sample thickness of 5.0 mm) in the presence of low molecular weight PP- g -MA ( M n = 800), the RL of −24.5 dB at 20.0 GHz was observed. Through simply changing M n of PP- g -MA from 800 to 8000, more oxidized iron resulted in a decreased permeability and smaller RL in the high frequency range. The in-situ-formed nanofillers significantly reduced the flammability of PP for potential wide applications.