Rheological Dependence on Dielectric and Microwave Absorption Properties of Carbon Black/Rubber Nanocomposites Over 6–18 GHz

A systematic study of the effects of the binder matrix on the microwave absorption properties of functional carbon nanoparticle-impregnated rubber composites is reported herein. Flexible rubber composites were fabricated by loading of conductive carbon black (CB) in three different elastomeric binder host matrices: silicone rubber, acrylonitrile butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM) rubber. The DC conductivity, morphology and complex dielectric permittivity were investigated using the four-point probe contact method, scanning electron microscopy and vector network analyzer instrumentation, respectively. The percolation threshold was found to be lowest for CB-silicone rubber composites, i.e. 6 wt.% loading of CB, followed by 12 wt.% for CB-NBR composites and 16 wt.% for CB-EPDM composites. The rheological behavior of these composites was also studied, and their correlation with the observed percolation threshold (DC conductivity) of composites is discussed. The microwave absorption properties (reflection loss [RL]) were calculated based on the measured electromagnetic parameters over a frequency range of 6–18 GHz for each composite system. The significant microwave absorption (RL >  −10 dB) properties can be tuned by varying the thickness in the range of 1.7–3.0 mm in these composites. The studies presented in the paper provide a basic framework for selection of an appropriate binder matrix for the development of stealth composites, according to the desired area of application.