Abstract:In this work, the results of investigation of the effect of polymer composite melts electrical conductance increase with time are presented. The conductance time dependencies were obtained for composites based on polypropylene filled with carbon nanoparticles of different types. The dependencies were analyzed to demonstrate the possibility of correlation of the conductance kinetics with different composite parameters, such as the filler geometry. Additional studies were carried out, such as electron microscopy… Show more
“…The g-C 3 N 4 dispersed polymer composites showed higher value of dielectric constant compared to pristine PVA, this could be as a result of uniform dispersion and a network of g-C 3 N 4 filler within the PVA/PANI/g-C 3 N 4 (1%, 3%, 5%) polymer, in addition to a anticipated interfacial polarization mechanisms. 62,63 The obtained dielectric constant values are similar to the reported in other PVA composites. 64,65 Figure 7.(a) Dielectric constant, (b) Dielectric loss (c) Conductivity (d) Impedance with respect to frequency for polyvinyl alcohol/polyaniline/graphitic carbon nitride (1%, 3%, 5%) composites.…”
A light weight electromagnetic interference (EMI) shielding and microwave absorbing composite films has been developed by loading varying weight content of graphitic carbon nitride (g-C3N4) nanosheets and polyaniline (PANI) into polyvinyl alcohol (PVA) matrix. The prepared PVA/PANI/g-C3N4 (1%, 3%, 5%) composites has been subjected to FTIR, X-Ray powder diffraction, SEM, Thermal studies, Dielectric studies and electromagnetic shielding effectiveness (EMI SE) analysis. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites was discovered to have improved electrical conductivity, dielectric loss, and dielectric constant. It is observed from the SEM images that the sheet layers of g-C3N4 are wrapped by the polymer matrix and the morphology to PVA/PANI composite in the g-C3N4 indicates homogeneous blending of PVA/PANI without any phase separation and has porous in it. The PANI/g-C3N4 fractured surfaces present are smooth but irregular in appearance indicating good compatibility between the PVA and PANI matrices. The dielectric properties was found to increase on increasing the concentration of the g-C3N4 nanofiller and reached a maximum of 9.8 × 106 at 1 MHz for 3% g-C3N4 in PVA/PANI. The incorporation of g-C3N4 into PVA/PANI enhanced the conductivity and the 5% g-C3N4 loaded composite film exhibited a conductivity value of 0.043 S/cm at 1 MHz. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites exhibited potential EMI SE values ranging from 24 to 35 dB at 8.6 GHz and from 42 to 63 dB at 12.4 GHz, for instance the PVA/PANI/g-C3N4 5% composite showed highest value of 63 dB at 12.4 GHz. The PVA/PANI/g-C3N4 5% exhibits the maximum highest reflection loss 8 GHz–12 GHz in which the higher absorption of −36 dB is observed at 10.3 GHz of the X-band region.
“…The g-C 3 N 4 dispersed polymer composites showed higher value of dielectric constant compared to pristine PVA, this could be as a result of uniform dispersion and a network of g-C 3 N 4 filler within the PVA/PANI/g-C 3 N 4 (1%, 3%, 5%) polymer, in addition to a anticipated interfacial polarization mechanisms. 62,63 The obtained dielectric constant values are similar to the reported in other PVA composites. 64,65 Figure 7.(a) Dielectric constant, (b) Dielectric loss (c) Conductivity (d) Impedance with respect to frequency for polyvinyl alcohol/polyaniline/graphitic carbon nitride (1%, 3%, 5%) composites.…”
A light weight electromagnetic interference (EMI) shielding and microwave absorbing composite films has been developed by loading varying weight content of graphitic carbon nitride (g-C3N4) nanosheets and polyaniline (PANI) into polyvinyl alcohol (PVA) matrix. The prepared PVA/PANI/g-C3N4 (1%, 3%, 5%) composites has been subjected to FTIR, X-Ray powder diffraction, SEM, Thermal studies, Dielectric studies and electromagnetic shielding effectiveness (EMI SE) analysis. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites was discovered to have improved electrical conductivity, dielectric loss, and dielectric constant. It is observed from the SEM images that the sheet layers of g-C3N4 are wrapped by the polymer matrix and the morphology to PVA/PANI composite in the g-C3N4 indicates homogeneous blending of PVA/PANI without any phase separation and has porous in it. The PANI/g-C3N4 fractured surfaces present are smooth but irregular in appearance indicating good compatibility between the PVA and PANI matrices. The dielectric properties was found to increase on increasing the concentration of the g-C3N4 nanofiller and reached a maximum of 9.8 × 106 at 1 MHz for 3% g-C3N4 in PVA/PANI. The incorporation of g-C3N4 into PVA/PANI enhanced the conductivity and the 5% g-C3N4 loaded composite film exhibited a conductivity value of 0.043 S/cm at 1 MHz. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites exhibited potential EMI SE values ranging from 24 to 35 dB at 8.6 GHz and from 42 to 63 dB at 12.4 GHz, for instance the PVA/PANI/g-C3N4 5% composite showed highest value of 63 dB at 12.4 GHz. The PVA/PANI/g-C3N4 5% exhibits the maximum highest reflection loss 8 GHz–12 GHz in which the higher absorption of −36 dB is observed at 10.3 GHz of the X-band region.
“…As it was mentioned in our other works, [ 7,8,12 ] more direct methods of the enriched surface layer presence verification, such as electron microscopy, Raman spectroscopy, and thin surface layers removal with consequent electrical resistance measurements, allowed to say that the enriched layer thickness is very low (<10 μm). Also, the phenomenon presence was observed for composites based on other types of polymers, such as PE and PS, and for different materials of mold components, such as electrodes and gaskets.…”
Section: Resultsmentioning
confidence: 77%
“…The procedure of molecular modeling is described in more detail elsewhere. [8] Additionally, it was shown that in the presence of even a fairly weak attractive potential between CNTs at high concentrations of . Middle -for the case of strong interaction between CNTs (Hamaker energy prefactor of 39.5 kcal mole −1 ) and strong CNT/wall interaction (wall Lennard-Jones dispersion energy of 5 kcal mole −1 ).…”
Section: Resultsmentioning
confidence: 99%
“…[4,5] However, interpretation given in these papers, such as dynamical agglomeration of nanoparticles, lacks universality, since it can lead to resistance decrease only in cases of already achieved percolation. [6][7][8] Also, it is unclear, how it is transpiring for different types of fillers, since this effect is usually explained on example carbon nanotubes (CNTs). Molecular dynamics (MD) simulations were conducted for composites, containing CNTs in amounts, surpassing percolation threshold for that type of filler.…”
Process of nanoscale carbon filler migration in polymer composite melts is studied. Monotonous decrease of electrical resistance is observed for composite materials during their stay in a melted state. This is especially pronounced for composites with concentration of filler much lower than percolation threshold determined for a specific matrix/filler/mixing method combination. This phenomenon can be observed for composites based on different polymer matrices. Also, it is demonstrated that the type and geometry of the electrically conductive filler does not affect presence of the phenomena. A setup for measurement of conductance for volume and surface layer components is used. The results of electrical conductance measurements of the polymer composite melt using this setup allows to attribute the increase of composite material conductance to formation of filler enriched surface layer. To obtain information on the processes occurring at the microscopic level, molecular dynamics simulations are conducted. Variation of several simulation parameters with comparison of the results to experimental data allows to understand the macroscopic composite material conductance behavior.
“…According to national standard GB/T 31838.3-2019, the straight fluid conductivity was measured at different elongation ratios using the three-electrode method [ 24 ]. The measurement device is shown in Figure 2 and the current value for each specimen under the condition of keeping the voltage stable for 10 min is used as the value of body conductivity current [ 25 ].…”
Mechanical stresses generated during manufacturing and laying process of high voltage cables can result in degradation of insulation properties, affecting the stable operation of the transmission system. Traditional test methods for testing the effect of mechanical stress on the insulation properties of polyethylene still have some shortcomings to be explored and it is able to explain the changes of the insulation properties of polyethylene under mechanical stress from a microscopic perspective. In order to further study the effect of stress on the insulation properties of polyethylene, microstructural changes, the breakdown field strength, conductivity and charge distribution of polyethylene at different elongation rates are investigated by a combination of experimental and molecular dynamics simulations. The results show that the increase in stress leads to a decrease in crystallinity and microcrystalline size of the material decrease. The untwisting and orientation of the polyethylene molecular chains during the stretching process can create cavities, resulting in an uneven sample distribution and thickness reduction, leading to a reduction in the breakdown field strength. Meanwhile, some crystal regions are transformed into amorphous regions. The loose amorphous regions facilitate the directional migration of carriers, resulting in the increase of conductivity. When the elongation ratio is smaller, the distance between the molecular chains increases and the trap depth of the specimen becomes shallower. This facilitates the migration of ions and electrons and increases the rate of decay of the surface potential. When the stretch is further increased, the trap depth will become larger, decreasing the decay rate of the surface potential and reducing the insulation properties of the polyethylene. Meanwhile, the molecular dynamics model of semi-crystalline polyethylene was developed to observe the microstructure and energy changes during the stretching process. The conclusions in terms of tensile tests were verified from a microscopic perspective.
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