Decrease In Volume Resistivity Research Articles

Multiscale Carbon Fibre-Carbon Nanotube Composites of Poly(Vinyl Chloride)-An Evaluation of Their Properties and Structure.

To date, there has been limited information in the literature on the application of carbon fibre-carbon nanotube systems for the modification of poly(vinyl chloride) (PVC) matrixes by micro- and nanometric fillers and an evaluation of the properties of the unique materials produced. This paper presents the results of newly designed unique multiscale composites. The advantages of the simultaneous use of carbon fibres (CFs) and carbon nanotubes (CNTs) in PVC modification are discussed. To increase the dispersibility of the nanofiller, CFs together with nanotubes were subjected to a sonication process. The resulting material was introduced into PVC blends, which were processed by extrusion. The ratio of components in the hybrid filler with CF_CNT was 20:1, and its proportion in the PVC matrix was 1, 5, and 10 wt.%, respectively. Comparatively, PVC composites modified only with carbon fibres were obtained. The structure, thermal, electrical, and mechanical properties and swelling resistance of the composites were studied. The study showed a favourable homogeneous dispersion of nanotubes in the PVC matrix. This enabled effective modification of the structure at the nanometric level and the formation of an interpenetrating network of well-dispersed hybrid filler, as evidenced by a decrease in volume resistivity and improvement in swelling resistance, as well as an increase in glass transition temperature in the case of PVC/CF_CNT composites.

Effect of Ca3(PO4)2 doped to basalt on the structure, electrical characteristics and spinnability

Ca3(PO4)2 is selected to be added to the basalt to simulate basalt mixed sludge in order to produce glass and continuous fiber. XRD and Raman are used to analyze basalt glass with varied Ca3(PO4)2 additions. Basalt glass is amorphous, according to XRD measurements. However, Ca3(PO4)2 alters the Raman spectra of basalt glass noticeably. Raman results show Ca3(PO4)2 increases the degree of polymerization of the glass, but the degree of polymerization decreases with the further increase of Ca3(PO4)2 content. The dielectric characteristics are tested at a frequency of 1 MHz. When the addition amount of Ca3(PO4)2 is 1 g, it has the lowest dielectric constant of 6.567. When the addition amount is 2 g, it has the lowest dielectric loss of 0.0026. The volume resistivity of the sample without Ca3(PO4)2 is 4.227 × 1013 Ω· cm (25 °C). With the increase of Ca3(PO4)2 content, the volume resistivity decreases, reaching the lowest 1.78 × 1013 Ω·cm when the addition amount is 2 g (25 °C). With the increase of Ca3(PO4)2 content, the fiber diameter becomes larger, the crack decreases and the fracture frequency decrease. So the sludge can be considered as an addition in the continuous fiber production.

Investigation of Hydrothermal Aging on Polyvinyl Chloride (PVC) Used in Medium Voltage Cables

This investigation deals with the effect of hydrothermal aging on the electrical insulating properties of polyvinyl chloride used in medium voltage cables. The evolution of dielectric properties (dielectric loss factor, dielectric constant, dielectric strength and volume resistivity) as a function of aging time and temperature has been studied. After that, the mechanical characteristics (elongation at break and tensile strength) were also determined. Physico-chemical analysis was performed to highlight the structural changes induced by hydrothermal aging. Infrared spectroscopy using the Fourier transform (ATR-FTIR) and thermogravimetric analysis (TGA-DTA) have been performed. The results obtained show that the loss factor and dielectric constant increase gradually with the increase of temperature, while the volume resistivity decreases. At 100℃, the general shape of the curves giving the evolution of dielectric properties as a function of aging time shows that both loss factor and dielectric constant increase while those of volume resistivity and dielectric strength decrease. In the case of 80℃, the loss factor decreases slightly and the dielectric constant remains almost constant with aging time, whereas the volume resistivity and dielectric strength increase. The activation energy varies with aging time. The impact of hydrothermal aging on the properties of the material has been established in this study. At the beginning of aging, the degradation is mainly due to the elimination of molecular HCl. At more advanced stages of aging, the degradation is attributed to the elimination of HCl and double bonds formation followed by a change in color. Other consequences of the degradation like crosslinking and swelling of the samples are also noticed.

Study on the Influence of Organic–Inorganic Interface Properties on Breakdown Strength and Thermal Properties of MgO/PLA Composites

Polylactic acid (PLA) is expected to be widely used in green power equipment manufacturing due to its good mechanical properties and biodegradability. In this paper, the effects of MgO with different particle sizes and mass fractions on the thermal and electrical properties of PLA composites were studied. The experiment found that with the increase in MgO particle sizes and mass fractions, the thermal conductivity of MgO/PLA composites showed a rising trend, which was up to 165.4% higher than that of pure PLA. However, the heat resistance first increases and then decreases. For the electrical properties of MgO/PLA composites, the breakdown strength and volume resistivity decrease with an increase in MgO particle size and mass fraction. In order to further study the influence mechanism of the introduction of MgO with different particle sizes and mass fractions on the thermal and electrical properties of MgO/PLA composites, molecular dynamics simulation was used to simulate the glass transition temperature (Tg) of PLA composites doped with MgO of different particle sizes, and it was found that MgO doping weakened the movement of the PLA molecular chain segment. Using density functional theory (DFT) calculations, it was found that in the MgO and PLA system, electrons have a tendency to migrate from the PLA matrix to MgO, which causes the formation of electron traps at the inorganic–organic interface and affects its electrical properties. The purpose of this study is to provide a theoretical reference for PLA composites in the manufacture of power equipment.

Influence of Solid TAIC on Crosslinking LLDPE by Electron Beam Radiation

Abstract In this work, solid triallyl isocyanurate (TAIC) has been fabricated and used as the crosslinking sensitizer for linear low density polyethylene (LLDPE) crosslinking application. First, 0 phr, 1.5 phr, 3.0 phr, 4.5 phr and 6.0 phr solid TAIC have been added into the LLDPE to study the radiation crosslinking results. The resulting samples are measured by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), etc. The results reveal that the crystallinity, melt point, elongation and volume resistivity decrease when the content of solid TAIC increases in LLDPE from 0 phr to 6.0 phr. However, adding a proper amount of solid TAIC (3.0 phr) can improve the crosslinking degree and tensile strength of LLDPE. Finally, the space charge distribution of the samples has been measured, and the possible mechanism of solid TAIC that affects the LLDPE electrical properties is proposed.

Ageing of Some Lacquers Due to Microbiological Stress

This paper shows the ageing study of some coatings and / or impregnation lacquers due to microbiological stress through fungal attack. Dielectric spectroscopy has shown that the dielectric losses of the investigated materials increase as result of microbiological ageing. The mean recorded increases are about 4 times for the alkyl-epoxy-melamine copolymer, 2 times for epoxy polymer and 1.5 times for urethane polymer in agreement with the mould coverage degree of about 20 %, 10 %, and 3 %, respectively. The fungal attack of the investigated polymers led to a decrease in volume resistivity of about 65 % for the alkyl-epoxy-melamine copolymer, 45 % for the epoxy polymer, and 14 % for polyurethane, in agreement with the increase of dielectric losses and degree of mold coverage of the samples. FTIR determinations have shown that fungal attack significantly increased the number of aliphatic -OH and C-H bonds and decreased the number of C-O bonds, respectively of C-O-C oxiran groups and C-C aromatic bonds. DSC thermograms recorded at different temperature ranges and the activation energies calculation for first major oxidation process indicate that after the fungal attack the thermooxidative reactivity of the investigated polymers increases.

Combined effect of modified titanium carbide (TiC) particles and ethylene alpha olefins (POE) on properties of ethylene propylene diene monomer (EPDM)/TiC/POE composites for electronic application

For the field of flexible electronic materials, titanium carbide (TiC) is still a new member that needs to be further investigated. In this study, the effects of surface modification, TiC content and ethylene alpha olefins (POE) amount on dielectric properties of ethylene propylene diene copolymer (EPDM) are investigated in detail. The addition of 20% modified TiC particles can improve the dielectric constant of EPDM control from 2.4 to 8.7 (360% increase) at 105 Hz. However, the complex viscosity of EPDM control increases by 6.4 times at 1.7 Hz and the volume resistivity decreases by 3 order of magnitude. Moreover, the thermal conductivity of EPDM control only increase by 17%. By comparison, the 20% POE not only increases the dielectric constant of EPDM/TiC (10/2) from 8.7 to 13.5 (55% increase) at 105 Hz, with slight decrease of volume resistivity, but also decreases the complex viscosity of EPDM/TiC (10/2) from 1.19 × 105 Pa·S to 5.78 × 104 Pa·S (51% decrease) at 1.7 Hz. Meanwhile, the addition of 20% POE can further enhance the thermal conductivity of EPDM/TiC (10/2) from 0.281 W/(m·K) to 0.416 W/(m·K) (48% increase).

Polydimethylsiloxane–PbZr0.52Ti0.48O3 nanocomposites with high permittivity: Effect of poling and temperature on dielectric properties

ABSTRACTPolydimethylsiloxane (PDMS)/lead zirconate titanate (PbZr0.52Ti0.48O3, PZT)‐based nanocomposites with high dielectric constant (permittivity, k) are prepared through room temperature mixing. The effect of PZT loading on electrical and mechanical properties of the PDMS–PZT composites is extensively studied. It is found that there is significant increase in permittivity with PZT loading and decrease in volume resistivity. All the composites have low dielectric loss compared to permittivity value. It is observed that there is increase in permittivity and decrease in volume resistivity of composites after poling, which is due to the dipolar polarization. It is found that both permittivity (ε′) and alternating current conductivity (σac) are increased with temperature at low frequency (1 Hz) and decreased with temperature at high frequency (1 MHz). The above composites are sensitive to external pressure and can be used as pressure/force sensor. The tensile strength and % elongation at break decreases with PZT loading, which is due to the nonreinforcing behavior of PZT ceramic. PZT particles distribution and dispersion in PDMS matrix are observed through field emission scanning electron microscopy, high resolution transmission electron microscopy, and atomic force microscopy/scanning probe microscopy. Thermal stability of composites increased with the PZT loading which is due to higher thermal stability of PZT particles compared to PDMS matrix. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47307.

Influence of Copper Particles on Breakdown Voltage and Frequency-Dependent Dielectric Property of Vegetable Insulating Oil

The insulating performance of oil is vulnerable to particles especially the conductive particles. This paper investigated the influence of copper particles of micrometer size on the breakdown strength and frequency-dependent properties of vegetable oil. The AC breakdown voltage of contaminated vegetable oil with copper particles of different numbers (ranging from 103 to 106) was measured. The frequency-dependent dielectric properties including volume resistivity, relative permittivity and dissipation factor of the contaminated vegetable oil with copper particles of various volumetric concentrations (0.011%, 0.056% and 0.112%) were measured. Identical experiments were conducted with mineral oil for comparison. Results show that the AC breakdown voltage of vegetable oil decreases with the increase of copper particle concentration. The mineral oil exhibits a similar trend, but the influence of copper particles on the AC breakdown voltage of vegetable oil is less significant than that on mineral oil because of its greater viscosity. The relative permittivity and dissipation factor increase with increasing copper volumetric concentration while the volume resistivity decreases. The influence of copper particles on them is significant at low frequencies and this influence becomes inconspicuous as the frequency increases. Similar results were observed for mineral oil.

Influence of addition of hydroxyl-terminated liquid nitrile rubber on dielectric properties and relaxation behavior of epoxy resin

Epoxy resin is one of the most popular insulation materials used in power equipment, whereas it is easy to crack when used in some large equipment due to its poor toughness. In order to increase the toughness of epoxy resin, adding liquid rubber into epoxy resin is a common way employed in industrial production. However, the dielectric properties of epoxy resin changes while the toughness increases. In this paper, hydroxyl-terminated liquid nitrile rubber (HTBN) was used as the filler to toughen the epoxy resin. Through comparing and analyzing the glass transition temperature and permittivity of composites with different filler contents, the influence of rubber particles on the mechanical and dielectric properties of epoxy resin was studied. The results indicate that the glass transition temperature decreases with the increase of filler content. When HTBN content is more than 15%, the toughness of composites is enhanced. With the increasing content of HTBN, the volume resistivity decreases, while the relative permittivity and dielectric loss tangent increase. The breakdown strength reveals little change. The addition of HTBN has a certain effect on the dielectric relaxation behaviors of epoxy resin, and the dielectric relaxation which caused by the interfacial polarization between rubber particles and epoxy matrix appears at the temperature above 5 °. Therefore, the influences of fillers on the dielectric properties should be considered while toughening the epoxy through adding liquid rubber during the formula design.

Effect of stretching on electrical properties of LDPE/MgO nanocomposites

This paper researched the effect of stretching on electrical properties of LDPE/MgO. Pulsed electro-acoustic (PEA) method, dielectric analyzer and high resistance meter were used to research the DC breakdown, space charge behavior, permittivity, loss tangent and volume resistivity of neat LDPE and LDPE/MgO nanocomposites with concentration of 1, 3 and 5 wt% with and without elongation ratio of 1.1. Results indicate that the DC breakdown strengths of neat LDPE and nanocomposites decrease after stretching. The heterocharges near electrodes in neat LDPE change to homocharges after stretching and a large amount of positive and negative charges accumulated in samples with concentration of 3 wt% and 5 wt%. Meanwhile, homocharges near cathode electrode in nanocomposite with concentration of 1 wt% decrease a little and a small amount of positive charges were observed in the samples after stretching. Furthermore, there are different increases in amplitudes of permittivity in all samples after stretching as well as the loss tangents especially in the frequency domain from 10−1–102 Hz. The results of volume resistivity show that comparing with the nanocomposite with concentration of 1 wt% whose volume resistivity decrease after stretching, larger volume resistivity is observed in neat LDPE and nanocomposites with concentration of 3 wt% and 5 wt%. As we know, the electrical properties of polymer based nanocomposites is dominated by interface between nanoparticles and polymer matrix. After stretching, the area of interface may increase, which may increase the amount and depth of charge traps. Additionally, the free volume may increase and the force stressed on polar molecular may decrease, leading to the change of electrical properties of nanocomposites.

Preparation and research of PAN/ZnO anti-static composite nano-fiber

In order to improve the anti-static performance of polyacrylonitrile( PAN) fiber,with PAN fiber as raw material,N,Ndimethyl acetamide( DMAC) as solvent,prepared PAN spinning solution. Then added different ratios of nano-Zn O,with good conductivity,to the PAN spinning solution by the method of ultrasound and mechanical stirring,prepared PAN / Zn O composite spinning solution. After that,PAN / Zn O nano-fibers with anti-static property were prepared by electrostatic spinning technique. The spin-ability of PAN spinning solution and PAN / Zn O spinning solution as well as the influence of different ratios of nano-Zn O to the crystallinity and the volume resistivity of PAN / Zn O nano-fiber are studied. The results indicate that the spinning solution has good spin-ability; when the concentration was 12%,spinning voltage was 18 k V,receiving distance was 15 cm,advancing speed was 0. 0005 mm / s,under the condition of electrostatic spinning,can get nanofibers with uniform fiber diameter,good parallel straight degree and smooth surface;with the increase of nano-Zn O content,the surface of PAN / Zn O nano-fibers become rough but no obvious change in crystallinity,and the volume resistivity decreases.

Surface resistivity of carbonaceous fiber/PTFE antistatic coatings

PAN (Polyacrylonitrile)-based carbonaceous fibers were prepared at the heat treatment temperature (HTT) range of 650 to 900 °C. The relationships among HTT, carbon content and volume resistivity of the carbonaceous fibers were investigated. The carbonaceous fibers/PTFE (Polytetrafluoroethylene) antistatic coatings were prepared by the spraying technology and the effects of carbonaceous fibers and pigments on surface resistivity of the coatings were systematically discussed. Micrographs provide insight into the antistatic mechanism of the coating. The results show that carbon content of the carbonaceous fibers increases from 68.8% to 74.8% (mass fraction) and the volume resistivity decreases drastically from 1.94×103 to 8.27×10−2 Ω·cm. The surface resistivity of the antistatic coating is adjustable between 105 and 108 Ω to fit the different antistatic materials. Static is dissipated by a conductive network of short fibers and the tunneling effect between the neighboring fibers and conductive pigments. Conductive pigments make the conductive network more perfect and improve the antistatic ability, but insulating pigments acting as barriers for the formation of conductive channel increases the surface resistivity of the coatings. The influence of pigments on the surface resistivity drops gradually with the decrease of the carbonaceous fibers volume resistivity.

Thermal aging on ethylene–propylene–diene rubber composites reinforced by samarium oxide, samarium borate and Sb in Sb doped SnO2

Ethylene–propylene–diene monomer (EPDM) rubber composites reinforced with 50 phr samarium oxide (Sm2O3), samarium borate (SmBO3) and Sb in antimony doped tin oxide (ATO) are aged at 150°C for different intervals. It is found that neutral Sm2O3 and alkaline SmBO3 can retard the oxidative degradation of EPDM by blocking radical passage. The acidic ATO particles can accelerate the oxidative degradation of EPDM. The trend of tensile strength of EPDM composites is consistent with that of cross-link density of EPDM composites. SmBO3 and ATO can retard the increase of dielectric loss until 10 days of aging, while Sm2O3 can keep the dielectric loss at low level until 14 days of aging. The increased surface charge of filler can make surface and volume resistivity decrease sharply. Antimony doped tin oxide can deteriorate the dielectric strength of EPDM, while SmBO3 and Sm2O3 can keep the dielectric strength of EPDM at a constant level.

Dynamic Mechanical Properties of PMN/CNFs/EP Composites

In this research, piezoelectric ceramic PMN(lead magnesium niobate-lead zirconate-lead titanate)/carbon nano-fibers(CNFs)/epoxy resin(EP) ccomposites were prepared and the dynamic mechanical properties and damping mechanism of PMN/CNFs/EP composites were investigated. The addition of CNFs into PMN/EP composite results in decrease of volume resistivity of the composite. When the concentration of CNFs is 0.6% weight of epoxy resin the volume resistivity of PMN/CNFs/EP composite is about 108 Ω·m. Dynamic mechanical analysis indicates that the loss factor, loss area, and damping temperature range of PMN/CNFs/EP composites increase with the CNFs content increasing till to 0.6% of weight of epoxy resin. When the CNFs content is more than 0.6% the damping properties of composites decrease oppositely. In PMN/CNFs/EP composites, the CNFs content 0.6% and the volume resistivity of PMN/CNFs/EP composites about 108 Ω·m just satisfy the practicing condition of piezo-damping, so the composites show optimal damping property.

Reducing resistivity of polyamide-6/multi-walled carbon nanotube composites by adding ultra-fine rubber particles on account of non-volume exclusion effect

The volume resistivity of polyamide-6(PA6)/multi-walled carbon nanotube (MWCNT) composites was found to be further reduced by adding a kind of ultra-fine rubber particle (URP) with average diameter of 150 nm due to non-volume exclusion effect. With the addition of 16 phr URP, the percolation threshold of PA6/MWCNT composites was reduced from 6 phr MWCNTs to 3 phr. Besides, at a constant loading of 4 phr MWCNTs, increase of URP loading led to two changes and a plateau for the volume resistivity of composites. The morphological observations of composites revealed that the decrease of volume resistivity was attributed to both homogenous dispersion and stretching of MWCNTs in PA6. The mechanism on better dispersion and stretching of MWCNTs with the help of URP was also given.

An innovative method to improve the electrical conductivity of multi-walled carbon nanotubes filled polyamide 6/polystyrene blends

An innovative method has been successfully developed to improve the electrical conductivity of polyamide 6/polystyrene (PA6/PS) blends in this paper. PA6/PS blends containing multi-walled carbon nanotubes (MWCNTs) are prepared by the radical polymerization of styrene in the presence of є-caprolactam (CL) and MWCNTs, followed by the in-situ anionic ring-opening polymerization of CL. In the resulted PA6/PS blends, MWCNTs are selectively located at the interface of PA6 and PS. Because the interface of 0.5 and 1.0 wt.% MWCNTs filled blends with PA6/PS weight ratio of 70/30 is continuous, a MWCNTs conductive pathway is formed in these two blends, which results in a decrease of volume resistivity by about 9 orders of magnitude.

Study on Mechanical, Thermal and Electrical Characterizations of Nano-SiC/Epoxy Composites

This report covers the results of a study on evaluating the effect of nano-SiC particles on mechanical, thermal and electrical properties of epoxy by lap shear, TGA, DSC and electrical tests. Epoxy composites filled with micro-SiC particles were also studied for comparison. The mechanisms of performance improvement were discussed in detail. The results showed that with identical loading, silane treated nano-SiC filled nanocomposites have the best properties. The volume resistivity decrease, dielectric constant e increase and loss tangent tan(δ) increase by addition of silane treated nano-SiC particles are smaller than those by the other fillers. Silane treatment of nanoparticles improves each performance, including increases shear strength, thermal stability, volume resistivity and decreases e and (δ). The addition of nano-SiC particles remarkably improves shear strength, e and tan(δ), while slightly enhances thermal stability of epoxy. 8 vol. % silane treated nano-SiC/epoxy composite has the highest shear strength 10.6 MPa with the maximum enhancement, 80%, over the neat resin. It also has good temperature independence of dielectric properties and enough volume resistivity, which meet the demand of some microelectronics materials.

Investigation of electrical conductivity and electromagnetic shielding effectiveness of polyaniline composite

With the increasing of electromagnetic pollution and the widely use of commercial and military products, there is an increasing interest in electromagnetic interference (EMI) shielding. This paper mainly aims at electrical conductivity and EMI shielding effectiveness (SE) of the conducting composites made from silicone rubber (SR) with different loading levels of HCl-doped polyaniline (PAN-HCl) in the low frequency range from 3 to 1500 MHz. The result indicates that SE of the composites increase and the volume resistivity decrease with increasing mass ratio loading of PAN-HCl in the SR. The measured SE of the composites are from 16 to 19.3 dB at 100 mass ratio loading of the PAN-HCl and the volume resistivity decrease nine orders of magnitude compared with that of the emeraldine base form of PAN (PAN-EB) composites.

Investigations of Electrical Properties in Silica/Indium Tin Oxide Two‐Layer Film for Effective Electromagnetic Shielding

The effect of zinc ions added to silica film on the electrical and structural properties of a silica/indium tin oxide two‐layer film which had been prepared by solution coating for electromagnetic shielding of displays was studied. The volume resistivity of the undoped silica/indium tin oxide film was more than 3 times as high as that of the zinc‐doped silica/indium tin oxide film. The addition of divalent cations, zinc ions, to the overcoated layer led volume resistivity of the two‐layer film to decrease significantly and also caused a long‐term increase in stability. The decrease in volume resistivity was due to the addition of zinc ions that changed the interface ionization and helped to enhance the electrical conductivity in the two‐layer film.