ABSTRACT
In this paper, we report the effect of metal oxide (Fe2O3) loading in different weight ratios (0.5%, 1%, 2%, and 4%) on the structural and electrical parameters, viz., the complex dielectric constant, electric modulus spectra, and the AC conductivity, of polymeric composites of PVDF/PMMA (30/70 weight ratio) blend. The structural and geometric measurements have been analyzed with the help of peak location, peak intensity, and peak shape obtained from XRD as well as from FTIR spectra. The electrical properties have been investigated using an impedance analyzer in the frequency range 100 Hz to 1 MHz. The real parts of the complex permittivity and the dielectric loss tangent of these materials are found to be frequency independent in the range from 20 KHz to 1 MHz, but they increase with the increase in the concentration of nano-Fe2O3. The conductivity also increases with an increased loading of Fe2O3 in PVDF/PMMA polymer blends. The electric modulus spectra were used to analyze the relaxation processes associated with the Maxwell-Wagner-Sillars mechanism and chain segmental motion in the polymer mix.
ABSTRACT
In this paper, we present the studies on electromagnetic interference (EMI) shielding effectiveness (SE) of K2CrO4-PMMA composites developed by two different methods: one in bulk form of thickness 1.2 mm and another by stacking twelve layers of thin films each of thickness 100 µm. The EMI SE of stacked twelve layers of 1.2-mm-thick composite films has been achieved until 23.2 dB in the frequency range 8.0-12.0 GHz. This is remarkably higher than the 17 dB achieved for the bulk composites of 1.2 mm thickness. The characteristic EMI SE graphs obtained using Agilent E82B Vector Network Analyzer in the X band frequency range have been depicted, and the shielding mechanism in these composites has been analyzed. It is found that the SE in this frequency range is dominated by absorption. The study suggests these composites to be a potentially promising material for EMI shielding purpose.
