The effect of modifier contents of polyvinyl pyrrolidone on the enhanced dielectric and microwave absorbing properties of multiwalled carbon nanotubes

Polyvinyl pyrrolidone (PVP) polymers were used as non-covalent modifiers to modify the surface of multi-walled carbon nanotubes (MWNTs) by ultrasonic dispersion method. The transmission electron microscope results suggest that a layer of polymers is wrapped on the surface of MWNTs, and the thickness is about 2.5 nm. The addition of PVP helps to facilitate uniform distribution of MWNTs and increases the interfacial multipoles formed between PVP and MWNTs, which plays an important role in the regulation of the dielectric parameter and the enhancement of the microwave absorbing properties. The effects of PVP loadings and thickness of PVP/MWNTs hybrids on the dielectric parameter of MWNTs are investigated. The microwave absorbing properties are calculated from the dielectric constants. The results show that the maximum reflection loss is -26.27 dB at 7.8 GHz while the loading of PVP on MWNTs is 8.0 wt % with a thickness of 3.0 mm. These results suggest that the PVP contents and absorber thickness are important factors for the improvement of dielectric loss and microwave absorption properties of MWNTs.