Electromagnetic interference shielding effectiveness of composites based on polyurethane derived from castor oil and nanostructured carbon fillers

Graphene nanoplatelets (xGnP), expanded graphite (EG), multiwall carbon nanotubes (MWCNTs), and carbon black (CB) were dispersed in various amounts in a thermosetting polyurethane (PU) matrix derived from castor oil and composite plaques were obtained by compression molding. The electrical percolation threshold was found to be 0.1 vol% for MWCNT, 0.5 vol% for xGnP, 2.8 vol% for CB, and 2.7 vol% for EG-filled systems. The relation between electrical conductivity, morphology, and electromagnetic interference shielding effectiveness (EMI SE) of the resulting composites was studied to understand how the EMI SE is influenced by morphology and electrical conductivity of each filler. The composites display significantly distinct EMI SE values, depending on the type of carbon filler and its volume fraction. Composite based in PU/EG and PU/xGnP exhibited the highest EMI SE values (70 and 47 −dB, respectively); however, PU/MWCNT composites showed higher EMI SE (24 −dB) value at the same filler content (3 vol%) than the other composite system.