Development of high performance EMI shielding material from EVA, NBR, and their blends: effect of carbon black structure

The conductive composites were prepared using two different types of conductive black (Conductex and Printex XE2) filled in matrices like EVA and NBR and their different blends. The electromagnetic interference shielding effectiveness (EMI SE) of all composites was measured in the X band frequency range 8-12 GHz. Both conductivity and EMI SE increase with filler loading. However, Printex black shows higher conductivity and better EMI SE at the same loading compared to Conductex black, and this can be used as a material having high EMI shielding effectiveness value. The conductivity of different blends with same filler loading generally found to increase slightly with the increase in NBR concentration. However, EMI SE has some dependency on blend composition. EMI SE increases linearly with thickness of the sample. EMI SE versus conductivity yields two master curves for two different fillers. EMI SE depends on formation of closed packed conductive network in insulating matrix, and Printex black is better than Conductex black in this respect. Some of the composites show appreciably high EMI SE (> 45 dB).