Microwave absorbing properties of linear low density polyethylene/ethylene–octene copolymer composites filled with short carbon fiber

Linear low density polyethylene/ethylene–octene copolymer composites filled with short carbon fiber were prepared by melt blending. The structure and surface morphology of the samples were characterized by scanning electron microscopy and transmission electron microscopy. The electromagnetic parameters were determined with transmission/reflection method in the range of 2.6–17.8 GHz, and microwave absorbing properties of the composites were determined using the arch method in the frequency range of 2.0–18.0 GHz. The experimental results show that short carbon fiber loading influences the absorbing peak position and reflection loss, and that the composites containing 30 wt.% short carbon fiber display two absorbing peaks. The maximum reflection losses achieve −15.66 dB at 4.6 GHz and −17.37 dB at 16.4 GHz. The bandwidth corresponding to the reflection loss below −10 dB amounts to about 3.6 GHz. The contribution for the microwave absorption comes from the dielectric loss. The theoretical calculation results of reflection loss are in agreement with the experimental results using the transmission line theory.