Toughened Epoxy Filled with Ferromagnetic Particles as High Temperature Resistant Microwave Absorbing Coating

In this work, microwave absorbing coatings consisted of toughened epoxy and ferromagnetic particles were prepared. The epoxy groups and isocyanate groups were investigated by Fourier Transform Infrared (FTIR) spectroscopy. Mechanical properties of the coatings are effectively improved comparing with the one employing unmodified epoxy in room temperature. After heat treat at 150 degrees C for approximate 100 hours, the coatings still have special impact strength between 45 and 50 Kg . cm according to Chinese National Standards GB 1732-1993 and flexibility about 2-3 mm according to Chinese National Standards GB 6742-2007. Complex permittivity epsilon(f) and permeability mu(f) of the ferromagnetic particles were measured using network analyzer in the frequency range from 2 to 18 GHz, to explain the reflection loss behavior of the coatings tested in microwave chamber. The morphology of ferromagnetic particles and their random dispersion in the coatings were observed by field emission scanning electron microscope (FESEM).