Foams of polycaprolactone/MWNT nanocomposites for efficient EMI reduction

Nanocomposites of polycaprolactone (PCL) filled with multi-walled carbon nanotubes (MWNTs) were foamed by supercritical CO2 in order to prepare materials with reduced electromagnetic interference (EMI). Two mixing techniques were used, i.e., melt blending and co-precipitation. Shielding efficiency as high as 60 to 80 dB together with a low reflectivity was observed at a very low vol% of MWNTs (0.25 vol%). The reflectivity of the nanocomposites was advantageously decreased upon foaming. The uniformity of the open-cell structure was assessed by scanning electron microscopy. These foamed PCL/MWNT nanocomposites are very promising EMI shielding materials because their performances result from absorption at low filler content and not from reflection at relatively high filler content as was previously the case.