Effect of Thermally-Reduced Graphene Nanoparticles on the Electromagnetic Interference Shielding Performance, Rheological Behavior and Thermal Stability of PP/PET Blend

Hypothesis: We investigated the effect of thermally-reduced graphene (TRG) nanosheets on electrical conductivity, dielectric constant, electromagnetic interference shielding performance, rheological behavior and thermal stability of polypropylene/polyethylene terephthalate (PP/PET) blend. For this purpose, 50/50 PP/PET blends were prepared through melt compounding in presence of different volume fractions of TRG. The direct current (DC) conductivity, the AC electrical conductivity and EMI shielding effectiveness of composites were measured. The morphology of blends was examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Findings: The morphology of the samples was co-continuous, and preferential localization of the nanoparticles led to a double percolated structure. This structure enhanced electrical conductivity of the samples considerably. The rheological analysis indicated that a percolated network was formed at low volume fractions of TRG. At 0.1 vol% loading, the conductivity of the composites satisfies the antistatic criterion (10−6 S/m) for thin films. At 2 vol% of graphene, a high electrical conductivity of0.16 S/m was achieved which was considered sufficient for electronic device applications. The dielectric constant and the electromagnetic interference shielding efficiency (EMI SE) of the blends significantly increased with TRG addition. By incorporating 2 vol% of TRG, the dielectric constant increased from 4 (for neat sample) to 9×107 at 10 Hz and the EMI SE increased from 1 dB (for neat sample) to 42 dB at 10 GHz, satisfying the target value for commercial applications. Thermogravimetric analysis (TGA) indicated that addition of TRG effectively enhanced the thermal stability of the samples. Incorporation of TRG not only increased the initial decomposition temperatures but also decreased the rate of decomposition. The enhanced thermal stability of the composites was attributed to the high aspect ratio of TRGs, which served as a barrier and prevented the emission of gaseous molecules during thermal degradation.