Electromagnetic interference shielding effectiveness of hybrid conductive polymer composite

Electromagnetic interference (EMI) shielding characteristics of ethylene vinyl acetate (EVA) and ethylene propylene diene (EPDM) and their 50:50 blend filled with conductive carbon black and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100-2000 MHz and 8-12 GHz (X-band range). The return loss and the loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with increasing frequency. The SE also increases with the increase in filler loading. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composites. The SCF-filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results suggest that the fibre-filled (greater than or equal to20 phr) composites can be used for the EMI shielding, as well as for some microwave applications.