Remarkable microwave heating performance of MWCNTs/polypropylene composites verified by electromagnetic-thermal coupling experiment and simulation

To explore the microwave heating technology of thermoplastic materials, multiple-walled carbon nanotube (MWCNT)/polypropylene (PP) composites with mass content of MWCNT ranging from 0.5 wt% to 6 wt% had been fabricated by melt blending. The as-prepared samples were heated in a commercial microwave oven with microwave frequency of 2.45 GHz for 5 s and their surface temperatures were recorded via an infrared thermal imager. The temperature of these samples reached its highest point when the mass content of MWCNT was 3 wt% and it could be heated to 290 degrees C in 5 s. The composites were also characterized by scanning electron microcopy (SEM), four-point probe method and vector network analyzer (VNA) to study the morphology, electrical performance and S-parameter respectively. The dc conductivity and morphology of the sample indicates that the effective three-dimensional conductive network is formed when the mass content of MWCNT is 1 wt%, and the microwave energy is converted into heat mainly in the form of conduction loss. Microwave heating mechanism of MWCNT/PP composites was studied by EM-thermal coupling and analyzing the absorbance (A), reflectance (R) and transmittance (T) calculated by S-parameters. The simulation results of EM-thermal coupling are consistent with the experimental results. The absorbance shows the samples' absorption of microwave energy and it has the same variation trend as the samples' temperature, which indicates that the microwave heating property of MWCNTs/PP composites can be estimated by its absorbance. Therefore, MWCNT can be considered as a potential microwave absorber for thermoplastic materials and its best content can be well estimated.