Morphology, electromagnetic properties and electromagnetic interference shielding performance of poly lactide/graphene nanoplatelet nanocomposites

Biodegradable poly lactide (PLA)/graphene nanoplatelet (GNP) nanocomposites with 0-15 wt% (0-9.1 vol%) of nanofiller were prepared. Scanning electron micrographs showed good dispersion of GNPs in PLA at low concentrations while above 6 wt%, GNPs were found to become physically in contact forming a 3D network within the matrix. X-ray diffraction showed that GNPs had a significant effect on the semi-crystalline structure of PLA which was also confirmed by differential scanning calorimetry measurements. Electromagnetic properties and electromagnetic interference shielding effectiveness of the nanocomposites were determined over C- and X-bands (5.85-12.4 GHz). It was observed that GNP embedding in PLA did not alter its magnetic permeability but enhanced its electrical permittivity and conductivity markedly leading to higher shielding effectiveness. The contributions of reflection and absorption to the overall shielding performance of the nanocomposites were determined and reflection was found to be the dominant shielding mechanism. However, the absorption potential of the samples increased by increasing GNP loading with the effective absorbance being more than 80% for a 1.5 mm-thick sample containing 15 wt% of GNPs compared to less than 0.6% for pristine PLA.