Electrical Properties Of Low Density Polyethylene Research Articles

Influence of Discharges and UV Irradiation on the Electrical Properties of High Pressure Polyethylene and Compositions on Its Base

ABSTRACT The composition and concentration of a low-molecular organic additive, leading to a significant improvement in the electrical properties of low-density polyethylene of high pressure grade 10,803-020, were experimentally determined. Phthalic anhydride and phthalic acid were used as modifying organic additives. The content of additives in the polyethylene of high pressure composition varied in the range of 0.01–0.1 wt%. It has been shown that the content of 0.05 wt% phthalic anhydride and phthalic acid in the composition polyethylene of high pressure (PEHP + 0.05 wt% PhAn + 0.05 wt% PhAc) is the optimal composition, since the electrical strength of the film has increased significantly. The dependences of the dielectric loss tangent and specific volumetric electrical resistance on temperature, as well as the kinetics of physicochemical changes in them under the influence of electrical discharges in air and UV irradiation, have been studied. It was established that the dielectric characteristics of the polymer composition PEHP + 0.05 wt% PhAn (storage life 40 years) changed slightly.

Effects of assisted electric field on the microstructure evolution and direct current electrical properties of low-density polyethylene

Low-density polyethylene (LDPE) is the basic material of the high-voltage direct current power cable insulation. The assisted electric field is a common way to regulate the microstructure of polymers, but its application in the field of electrical insulating polymers is rarely reported. To study the effect of the assisted electric field on the microstructure evolution and direct current (DC) electrical properties of LDPE, the LDPE treated with assisted electric field at the melting stage, cooling stage and the whole stage (i.e., the melting stage and cooling stage) are prepared together with the untreated LDPE, respectively. The effect of the assisted electric field applied at the different stages on the microstructure evolution of LDPE is characterized by the scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The DC electrical properties of the untreated LDPE and the LDPE treated with the assisted electric field are investigated via the breakdown strength, conductivity, space charge and surface potential decay measurements, respectively. The results show that, compared with the untreated LDPE, the LDPE treated with the assisted electric field at the whole stage has the smallest spherulite size and the largest spherulite number, followed by the LDPE treated at the cooling stage and the melting stage, respectively. The application of assisted electric field at different stages can significantly improve the DC electrical properties of LDPE. Compared with the untreated LDPE, the breakdown strength of the electric field assisted LDPE under the melting stage, the cooling stage and the whole stage increases, whereas the conductivity and space charge accumulation of the electric field assisted LDPE decrease greatly. The DC electrical properties of LDPE treated with the assisted electric field under the whole-stage are the best. Compared with untreated LDPE, the breakdown field strength of LDPE with whole-stage treatment can be increased by 35.8 %, the conductivity is decreased by 72.0 %, and the space charge accumulation is reduced by 20.2 %. More and smaller spherulites lead to the formation of more interface paths and introduce more deep traps, which contributes to the improvement of DC electrical characteristics of the electric field assisted LDPE. This work provides a new idea for the improvement of DC electrical properties of polymers.

Investigation of Electrical Properties of BiFeO3/LDPE Nanocomposite Dielectrics with Magnetization Treatments.

The purpose of this paper is to study the effect of nano-bismuth ferrite (BiFeO3) on the electrical properties of low-density polyethylene (LDPE) under magnetic-field treatment at different temperatures. BiFeO3/LDPE nanocomposites with 2% mass fraction were prepared by the melt-blending method, and their electrical properties were studied. The results showed that compared with LDPE alone, nanocomposites increased the crystal concentration of LDPE and the spherulites of LDPE. Filamentous flake aggregates could be observed. The spherulite change was more obvious under high-temperature magnetization. An agglomerate phenomenon appeared in the composite, and the particle distribution was clear. Under high-temperature magnetization, BiFeO3 particles were increased and showed a certain order, but the change for room-temperature magnetization was not obvious. The addition of BiFeO3 increased the crystallinity of LDPE. Although the crystallinity decreased after magnetization, it was higher than that of LDPE. An AC test showed that the breakdown strength of the composite was higher than that of LDPE. The breakdown strength increased after magnetization. The increase of breakdown strength at high temperature was less, but the breakdown field strength of the composite was higher than that of LDPE. Compared with LDPE, the conductive current of the composite was lower. So, adding BiFeO3 could improve the dielectric properties of LDPE. The current of the composite decayed faster with time. The current decayed slowly after magnetization.

Effect of Nanoparticles on the Morphology, Thermal, and Electrical Properties of Low-Density Polyethylene after Thermal Aging.

This paper investigates the morphology, thermal, and electrical properties of LDPE (low-density polyethylene)-based nanocomposites after thermal aging. The FTIR (Fourier transform infrared spectroscopy) spectra results show that thermo-oxidative reactions occur in neat LDPE and LDPE/SiO2 nanocomposites when the aging time is 35 days and in LDPE/MgO nanocomposites when the aging time is 77 days. Specifically, LDPE/MgO nanocomposites delay the appearance of thermo-oxidative reactions, showing anti-thermal aging ability. Furthermore, nanocomposites present lower onset degradation temperature than neat LDPE, showing better thermal stabilization. With regard to the electrical properties, nanocomposites maintain the ability to suppress space charge accumulation after thermal aging. Additionally, in comparison with SiO2 nanocomposites and neat LDPE, the permittivity of LDPE/MgO nanocomposites changes slightly after thermal aging. It is concluded that LDPE/MgO nanocomposites have better insulation properties than neat LDPE after thermal aging, which may be caused by the interface introduced by the nanoparticles.

Trap Modulated Charge Carrier Transport in Polyethylene/Graphene Nanocomposites

The role of trap characteristics in modulating charge transport properties is attracting much attentions in electrical and electronic engineering, which has an important effect on the electrical properties of dielectrics. This paper focuses on the electrical properties of Low-density Polyethylene (LDPE)/graphene nanocomposites (NCs), as well as the corresponding trap level characteristics. The dc conductivity, breakdown strength and space charge behaviors of NCs with the filler content of 0 wt%, 0.005 wt%, 0.01 wt%, 0.1 wt% and 0.5 wt% are studied, and their trap level distributions are characterized by isothermal discharge current (IDC) tests. The experimental results show that the 0.005 wt% LDPE/graphene NCs have a lower dc conductivity, a higher breakdown strength and a much smaller amount of space charge accumulation than the neat LDPE. It is indicated that the graphene addition with a filler content of 0.005 wt% introduces large quantities of deep carrier traps that reduce charge carrier mobility and result in the homocharge accumulation near the electrodes. The deep trap modulated charge carrier transport attributes to reduce the dc conductivity, suppress the injection of space charges into polymer bulks and enhance the breakdown strength, which is of great significance in improving electrical properties of polymer dielectrics.

Effect of EVA Content upon the Dielectric Properties in LDPE-EVA Films

Low density polyethylene (LDPE) blends with different percentages of ethylene vinyl acetate polymer membranes were prepared by a hot press casting method. The effects of EVA content on the electrical properties of LDPE were studied. The results on the electrical properties revealed that the surface resistance, volume resistivity, and breakdown voltage of the LDPE decrease with EVA content and reach a minimum at a 30 wt% of EVA. Dielectric constant and dielectric loss factor were increased with increasing EVA content up to 30 wt% of EVA. It can be deduced that the electrical properties of LDPE are improved by blending with EVA.

Optical, Electrical and Thermal Properties of Jute and Glass Fiber Reinforced LDPE Composites

Jute and glass fiber reinforced low density polyethylene (LDPE) composites were prepared using compression molding technique at 120° C with various percentage of fiber content. Thermal, optical and electrical properties of both composites were studied in this article. Thermal analysis of the composites confirmed the better thermal stability of glass fiber LDPE composites than that of the jute composite. Superposition of the absorption of LDPE and glass fiber in the composites has been confirmed by the peak and line shape of absorptions. The absorption peaks also indicates a better conjugation between the elements of composites. Electrical studies suggest that for both composite capacitance decreases with increase in frequency and voltage, which suggests good electrical properties of LDPE based composites.

Effect of Blending on Electrical Conduction and Breakdown of Low-Density Polyethylene Films with Different Densities

In this study, the effect of blending on physical and electrical properties of low-density polyethylene (LDPE) was investigated. Two kinds of LDPEs whose densities are evaluated to be 0.9179 g/cm3 and 0.9192 g/cm3, respectively, were used and blended according to different blend ratios. The LDPE with a blend ratio of 50 wt% had the lowest impulse breakdown strength, FBImp, at 30°C. However, the LDPE with a blend ratio of 50 wt% also had the highest FBImp at 90°C among all specimens. The DC breakdown strength, FBDC, decreased with the increase of the blend ratio at 30°C but increased at 60°C and 90°C. However, the FBDC did not depend on the blend. The current densities for all specimens were almost the same at 30°C, but decreased with a blend ratio up to 75 wt% at 90°C. By analyzing X-ray diffraction (XRD) patterns, we found that the crystal size in the (020) plane increased with a blend ratio up to 50 wt%, and the LDPE with a blend ratio of 50 wt% had the largest crystal size in the (020) plane among all specimens. It was found that the FBImp was strongly related to the crystal size in the (020) plane.

低密度ポリエチレンの電気特性に対するブレンド効果

低密度ポリエチレンの電気特性に対するブレンド効果

Volume and surface resistivity of low-density polyethylene filled with stainless steel fibres

D.c. electrical properties of low-density polyethylene filled with stainless steel fibres have been studied at various concentrations above the percolation threshold. The volume fractions used were 2, 5 and 10% of stainless steel fibre. The volume resistivity of polyethylene varied between 6.15×107 Ω cm at 2% loading level and 3.71×105 Ωcm at 10%. Corresponding values for surface resistivity varied between 2.77×107 Ω at 2% and 3.94×104 Ω at 10%. The value of the critical exponent for percolation was estimated to be around 2.4 for volume resistivity and 3 for surface resistivity.

The dielectric behaviour of polymers irradiated at 5 K

An investigation has been made of the effects of γ and reactor radiation at the temperature of liquid helium on varius electrical properties of low-density polyethylene (LDPE) and polyimide. Following radiation doses in the range up to 10 6 Gy of γ and 5 × 10 6 Gy of reactor, charging and discharging currents were measured in LDPE at 5 K. This demonstrated that the dominant mechanism of charge transport was some form of polarisation, with reactor irradiation producing the greater polarisation signal. Subsequent measurements of the dielectric breakdown strenght did not, howevever, indicate any difference between γ and reactor-irradiated samples. The investigation of polarisation processes and hence dielectric loss has been extended using Frequency Domain Dielectric Spectroscopy and Thermally Stimulated Discharge Currents. Initial results are presented for LDPE and polyimide γ-irradiated to 10 5 Gy at 5K.

Effects of nuclear radiation on electrical properties of low-density polyethylene at 5 K

Samples of low-density polyethylene film (LDPE) were irradiated at the temperature of liquid helium to doses of 10 5 Gy of reactor radiation and 10 6 Gy of gamma radiation from a 60 Co source. Following irradiation the test specimens were maintained at 5 K and subjected to certain electrical tests. Isochronal current/voltage measurements were made on gamma-irradiated samples and the dielectric breakdown strength of all specimens irradiated to 10 5 Gy was determined using a Marx generator. The results show no significant effect of radiation to 10 5 Gy on the dielectric strength. Also no significant effect of gamma radiation on the electrical conductivity was evident up to 10 5 Gy. The results here indicate that the dominant charge transport process was some form of polarisation. At 10 6 Gy and high applied fields, however, a previously unobserved electric pulse activity was noted, the source of which might be frozen-in space-charge fields.