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The estimation of charge density distribution in polyethylene (PE) especially at the interface region with conducting material such as copper (Cu) is essential at high field conduction. The magnitudes of space charge at that interface depend on the applied electric field and the electrode material. In this work, the charge density is computed for a slab model of Cu (111)/PE (001) in its pure condition and then with chemical impurities present in the PE chains. The density-functional theory (DFT) is used as a computational quantum mechanics to evaluate the charge density in the interface region. An electric field is applied between vacuum regions attached to the model to study the effect of presence of chemical impurities on the distribution of charge density along the interface. The chemical impurities used in this study are carbonyl, vinyl and conjugated double bond. It is found that the peak value of negative charge density near the Cu atoms at the interface region decreases as the impurity-created barrier height decreases. It is also found that changes in the charge density near the interface region occur only within 6 $\text{A}^{\mathrm {o}}$ inside PE chains; the charge density becomes constant thereafter, i.e., in the PE bulk. This paper reveals that the position of chemical impurities in PE chain influences the maximum change in charge density relative to its bulk values. The maximum change in charge density is found to be related to the trap depth in PE band gap, which is created by the presence of chemical impurities. It is concluded that the charge density distribution is affected by chemical impurities in PE and, in turn, affects the charge accumulation process.

Voltage stabilizers have the potential to improve the overall insulation properties of polymeric cables, but the poor compatibility with the polymer matrix limits their practical application. In this work, the reaction of 2,4-dihydroxybenzophenone (DHBP) with maleic anhydride (MAH) provides a novel and reactive aromatic ketone voltage stabilizer 4-(4-benzoyl-3-hydroxyphenoxy)-4-oxobut- 2-enoic acid denoted by MDVS, which can be grafted onto the backbone of polyethylene (PE) during the cross-linking process. The physicochemical and dc insulation properties of the cross-linked PE grafted with different addition of MDVS (XLPE-g-MDVS) are investigated, and the underlying mechanism is discussed. In comparison with the pristine XLPE, substantially suppressed space charge accumulation and decreased electrical conductivity are obtained in the XLPE-g-MDVS materials. As the content of MDVS is 1.2 wt%, XLPE-g-MDVS materials exhibit higher breakdown strength than that of the pristine XLPE. Furthermore, the graftable voltage stabilizer MDVS presents more efficient stabilizing effect than conventional voltage stabilizer DHBP before and after high-temperature degassing. Thermally stimulated current (TSC) tests and quantum chemical calculations are consistent with the experimental results of insulation properties, illustrating that capture and trap mechanisms cooperate in the improvement of XLPE dc insulation performance. [ABSTRACT FROM AUTHOR]

In the present study, biocompatible nanofibers containing aqueous extracts from Muscari neglectum (M. neglectum) plants (produced nanofiber) were prepared and their antifungal and cytotoxicity effects were investigated. For this purpose, the extracts obtained from flowers, stem leaves, and fresh onion from M. neglectum were lyophilized at various concentrations. Produced nanofibers were prepared using electrospinning techniques. During the electrospinning process, two auxiliary natural polymers including gelatin and chitosan were used. After synthesis, the physicochemical properties of the nanofibers were confirmed by Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray energy diffraction spectroscopy (EDS or EDX), and Differential Scanning Calorimetry (DSC). The electrospun produced nanofibers have continuous and uniform structures. The cytotoxicity assay of these electrospun nanofibers were done on Human dermal fibroblast cell (HDF) and HUVEC cell (Human Umbilical Endothelial Cells) lines and results showed that nanofiber doesn’t have any toxicity to normal cell lines. For anti-fungal activity tests, the appropriate amounts of nanofibers containing M. neglectum were placed in media with five different fungal species utilizing two methods: disc diffusion and well diffusion. In vitro results showed that all electrospun nanofibers containing M. neglectum had strong antifungal activity against Candida albicans, Glabrata, Parapacillus, Guillermoides, Crocus fungi species. Our findings also showed that nanofibers containing 86.88% polyvinyl alcohol/ gelatin/ chitosan/ M. neglectum root extract (produced nanofibers) were had better swelling and physicochemical properties and stronger antifungal activity than others (fiber formed with plant root). In a nutshell, natural nanofibers can be used as a beneficial drug delivery system. [ABSTRACT FROM AUTHOR]

In this article, a novel approach is proposed for accurate moisture content (MC) estimation of cross-linked polyethylene (XLPE) insulation employing electric modulus. Additionally, the variation of real and imaginary part of electric modulus in the argand plane is fitted using Cole-Cole (C-C) model for understanding of distributed relaxation behavior of XLPE insulation. Based on the frequency variation of dielectric parameters, five moisture sensitive parameters are identified and using these parameters, five empirical relationships are proposed for quantitative assessment of MC in XLPE insulation. It is observed that parameters obtained from the complex modulus spectrum yields better accuracy in estimation of MC compared to the parameters obtained from traditional frequency domain spectroscopy (FDS). [ABSTRACT FROM AUTHOR]

Energy harvesting is a promising strategy utilizing renewable energy to power low-power-consumption electronics, such as wireless sensor network (WSN) nodes and wearable electronics. In this article, a tape-like vibrational energy harvester, using flexible fluorinated polyethylene propylene (FEP) piezoelectret films as transduction material, is reported. Due to a specific air-filled parallel tunnel structure, the FEP piezoelectret films in this study exhibit both significant longitudinal and transverse piezoelectric effects and could be made into tape-like flexible transduction devices. The results show that the experimental data are consistent with the theoretical prediction and the finite-element method (FEM) calculation. For a device with an effective area of 18 mm $\times25$ mm and a seismic mass of 0.195 g on one edge, the output power at a resonant frequency of 16 Hz amounts to 3.1 $\mu \text{W}$ for an acceleration of 1 ${g}$. Owing to the tape-like and flexible transduction elements, the power generated by the device can be enhanced readily by either enlarging area of the transduction elements or multiplying a few transduction elements in series or parallel to meet the power requirement of electronic devices, which makes the practical application flexible. [ABSTRACT FROM AUTHOR]

Space charge dynamics in a low-density polyethylene (LDPE) film is calculated using mobility based on the Gaussian disorder model (GDM), which is commonly used to describe hopping conduction in disordered materials. The GDM exhibits a negative differential mobility under a strong positional disorder. In simulations, injected charges do not form packet-like space charges when using a constant mobility model, whereas packet-like space charges appear when using the mobility based on the GDM. The simulation using the GDM mobility can reproduce the time and voltage dependences of space charge behavior in LDPE. The calculated space charge, electric field, and current density profiles show good agreement with experimental results. [ABSTRACT FROM AUTHOR]

This article generalizes studies of corona electrets based on polymer composite materials. It describes processes that occur in polymer materials under corona discharge and responsible for the electret property magnitudes. Changes that take place in fine filler-loaded polymers can both increase and decrease electret properties and their stability over time. Optimal filler content in polymer materials that results in electret property enhancement by the factor of 2–2.5 is 2–6 vol%. At this filler loading reasons that induce growth of electret properties prevail. This article gives examples of new electret applications—in food packaging, antibacterial facial mask manufacturing, and oil recovery. [ABSTRACT FROM AUTHOR]

Cross-linked polyethylene (XLPE) is widely used as insulation material in high-voltage cables. Impurities, moisture, microvoids, extrusion technology, and other factors all have an effect on insulation properties. However, the primary of this article focus is the self-decomposition characteristic of the cross-linking agent in the cross-linkable polyethylene during the storage process. In general, cross-linkable polyethylene used for 220-kV power cables must be manufactured to cable within one year. However, no studies have been conducted on the performance and stability of cross-linkable polyethylene and its usability during the long-term storage process. As a result, an accelerated storage experiment is carried out in this article to simulate the long-term storage of the cross-linkable polyethylene at room temperature. The electrical and mechanical properties of XLPE samples made from the cross-linkable polyethylene with different equivalent storage times are then measured. The storage activity refers to the activity of dicumyl peroxide (DCP) acting on the properties of the cross-linkable polyethylene after long-term storage because the DCP will be decomposing slowly over time. The result shows that, as storage time increases, the storage activity of the cross-linkable polyethylene decreases due to the gradual decomposition of cross-linking agents in granules. When the XLPE is made from cross-linkable polyethylene stored for an extended period, the cross-linking degrees decrease, and mechanical properties deteriorate significantly. Long-term storage, on the other hand, aids in the improvement of crystal structures and, to some extent, increases ac breakdown strength. The final XLPE properties still meet the Chinese National Standard after one-year storage of the cross-linkable polyethylene. After two years, the thermal extension property, i.e., the elongation under load, is close to the requirements of the Chinese National Standard. However, after five years, the thermal elongation property has degraded to the point where it is no longer acceptable. [ABSTRACT FROM AUTHOR]

Due to significant radiation hardness, thermal properties, low sensitivity to gamma rays, and fast response, the 4H-SiC detector exhibits promising properties in measuring the neutron production in the high-power fusion devices. To demonstrate the potential value of the 4H-SiC detectors as a neutron flux monitor and a neutron spectrometer on experimentally advanced superconducting tokamak (EAST) during the 2021 EAST deuterium–deuterium plasma experimental campaigns, the 4H-SiC detector covered with a 25- $\mu \text{m}$ -thick 6LiF film 95% enriched in 6Li and the 4H-SiC detector covered with a 1.5-mm-thick polyethylene layer were installed on a viewport located at the mid-plane of port F outside the EAST vacuum vessel and operated continuously during the whole experimental campaign with the goal to measure both the total and the time-dependent neutron emission from the plasma. The results are compared with those obtained with detectors routinely working at EAST (235U Fission Chambers). Despite their small active volumes, the 4H-SiC detectors were able to measure the total and the time-dependent neutron emission with good reliability and stability. The results of this work not only demonstrated the satisfactory performance of the 4H-SiC detector in the harsh environment of a mixed neutron–gamma high-radiation field and strong electromagnetic field, but also its applicability as a neutron spectrometer and a neutron flux monitor for fusion deuterium–plasma experiments. [ABSTRACT FROM AUTHOR]

One of the key factors required in tissue engineering/ regeneration is to create a dynamic platform to increase the interaction of cells in response to various stimuli. In this context, facile synthesis of modified polyethylene glycol (FL PEG) encapsulated Iron Oxide nanoparticles [PoeM (Fe) NPs] is reported for its wound healing application in presence of an external magnetic field. Iron Oxide nanoparticles (8 ± 2nm) are synthesized and coated with FL PEG resulting in the formation of PoeM (Fe) NPs. The synthesized nanoparticles are characterized for their UV-Vis absorbance, DLS and TEM. These PoeM (Fe) NPs show excellent biocompatibility and enhanced wound healing activity in L929 fibroblasts when compared with control groups. This study could pave the way for the development of novel biomimetic nanosystems for wound healing applications. [ABSTRACT FROM AUTHOR]

Several fluorinated polyethylene surface studies have proved that the fluorination reaction can effectively prevent charge from being injected into polyethylene. Therefore, this paper explores the influence of fluorinated electrode on space charge behavior in polyethylene. In this study, the space charge distribution inside polyethylene is measured by laser-PWP (Pressure Wave Propagation) method while altering electrode fluorination duration and fluorination temperature. The experimental results show that measured homocharge injection is increased in polyethylene to which a fluorinated semiconductive electrode is heat pressed. Attenuated Total Reflectance-Infrared (ATR-IR) spectroscopy and Scanning Electron Microscope (SEM) are also performed, revealing that the fluorinated layer of semiconductive electrode on the interface between polyethylene and electrode block impurities from entering polyethylene. The measured space charge distribution, being the planar average amount, also reveals impurity generation since heterocharge formation is observed. As such impurities are blocked, in the meantime the electrodes' homocharge injection remains un-affected, thereby the measured apparent charge is greatly increased. [ABSTRACT FROM AUTHOR]

Studying the influence of short chain branch (SCB) on the crystal properties and breakdown strength of low-density polyethylene (LDPE) plays an important role in improving the electrical and mechanical properties of LDPE by adjusting the molecular structure. In this work, the SCB and long chain branch (LCB) content of LDPE are quantitatively characterized. Grain size, crystallinity and breakdown strength of LDPE (including AC and DC) are calculated through related characterization experiments. The results show that the SCB content in LDPE is dozens of times that of LCB. Reducing the SCB content can reduce the grain size of 110 face in LDPE and improve the AC and DC breakdown strength. The trap distribution characteristics measured by the thermally stimulated depolarization current (TSDC) method show that the SCB inhibits the formation of deep cavity defects in the LDPE interface area and decreases the trap energy level of crystal defects. This inspired us to improve the breakdown strength by reducing the SCB content in LDPE. [ABSTRACT FROM AUTHOR]

In order to quantitatively analyze the interaction effects of crosslinking byproducts on charge characteristics in crosslinked polyethylene (XLPE), samples are prepared by soaking additive-free untreated polyethylene in three major byproducts, namely acetophenone (A), cumyl alcohol (C), and a-methylstyrene (M), and space charge measurement under relatively low electric fields of 3, 5, 7, and 10 kV/mm is carried out. The results show that the effect of C on space charge accumulation is comparable with that of A per unit byproduct content, and M exhibits the weakest effect. It is related to the different dissociation degrees of byproducts under different electric fields. An exponential fitting formula is proposed to clarify the significant synergistic and the antagonistic effects of the byproducts on charge accumulation. The synergistic effects on charge accumulation is obvious in LDPE-MC (LDPE soaked in the blend of M and C) at 3,7, and 10 kV/mm, but not at 5 kV/mm, and the LDPE-AC (LDPE soaked in the blend of A and C) shows the same rule at 5, 7, and 10 kV/mm, except for 3 kV/mm. The LDPE-AM (LDPE soaked in the blend of A and M) has antagonistic effects on charge accumulation at 5, 7, and 10 kV/mm, and shows a trend from synergistic effects to antagonistic effects at 3 kV/mm. For LDPE-ACM (LDPE soaked in the blend of A, C and M), synergistic effects are dominant at 3, 5 and 7 kV/mm, then antagonistic effects are obvious at 10 kV/mm. The different rule on space charge accumulation may be due to the discrepant charge injection under different electric fields according to the results of charge distribution with individual byproducts. [ABSTRACT FROM AUTHOR]

It is shown that the concentration of single-walled carbon nanotubes in polyethylene can be estimated using a spectral-correlation method, which consists of statistical processing of random intensity distributions (speckles) formed by scattering on optical inhomogeneity of the material. The optimal conditions for performing measurements are established, possible causes of errors are determined, and the statistical errors of measurements are estimated. Based on experimental data, expressions are obtained for approximating the dependence of the nanotube concentration on the half-width of the normalized cross-correlation function of the intensity distributions of backscattered radiation at different wavelengths. The possibility of using extrapolation of calibration dependencies for two different physical models (linear and exponential) is considered and the expediency of using a linear model at nanotube concentration above 2% is shown. The concentration of nanotubes in one of the elements of the high-voltage coupling design is evaluated and the possibility of detecting inhomogeneity of the filler concentration in the material is demonstrated. [ABSTRACT FROM AUTHOR]

To suppress space charge accumulation and minimize the antioxidant migration, polyethylene (PE) grafted with reactive hindered amine antioxidant MC prepared by melt radical grafting is investigated in this work. Fourier transform infrared spectroscopy is used to investigate the grafting reaction, which shows that the antioxidant MC is successfully introduced onto PEe Space charge distribution, DC conductivity, DC breakdown strength and thermally stimulated current are measured and the electronic structure is calculated from first-principles. The results show that PE grafted with antioxidant MC can effectively suppress space charge accumulation, reduce DC electrical conductivity and enhance DC breakdown strength. The polar functional groups of antioxidant MC anchored on PE macromolecular chain form immobile deep traps at the grafted MC sites, which can capture space charges and scatter charge carriers to reduce the amount, mobility and energy of charge carriers. Seen from the oxidative induction time of the specimens before and after acetone extraction, the level of retention of the grafted antioxidant MC are significantly higher than those of conventional antioxidant 300 and antioxidant 4020, which indicates that PE grafted with antioxidant MC has excellent long-term thermal oxidation stability. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method for characterizing the trap energy distribution of polymers. The method can accurately extract the de-trapping current from the polarization current of the sample, thus overcoming the accuracy problem of the traditional isothermal relaxation current (IRC) method. Further application of this method on crosslinked polyethylene (XLPE) sheet samples revealed the effect of thermal degradation degree on the trap distribution of XLPE. At the recrystallization stage as polyethylene becomes re-crosslinked, the number of traps decreases. At the thermal-oxidative aging stage as the sample is seriously damaged, the number of traps increases. The de-trapping current of the sample thus exhibits a first decreasing and then increasing trend. [ABSTRACT FROM AUTHOR]

This review highlights the updated picture of charge transport in polymer dielectrics and offers suggestions for future research. It begins with the backgrounds of the various theoretical charge transport models and the underlying concepts of the physical quantities. The techniques for deriving the microscopic physical quantities, e.g., the Marcus parameters and the spectral density of bath, from first-principles methods are outlined for tutorial purposes. Our recent multi-scale simulation studies are presented to demonstrate how and why the macroscopic charge transfer behavior can be predicted from these microscopic quantities, without the use of phenomenological/ empirical models nor ad hoc parameters. Some new insights gained through the multiscale modeling technique are summarized, with a focus on the relation between the chemical structure of polymers and the carrier transport properties. Finally, what is further required for computer-aided (rational) dielectric polymer design is discussed. [ABSTRACT FROM AUTHOR]

Simultaneous measurement at various temperatures of space charge and relaxation current is performed on cross-linked polyethylene (XLPE)/ethylene-propylene-diene monomer (EPDM) double layers with and without silicone grease. The simultaneous measurement correlates the charge distribution and current information for the same sample and avoids discrepancy, due to the separate measurement on different samples. It is found that the polarity of interfacial charges change to the opposite with the increase in temperature in most samples, which is related to both Maxwell-Wagner polarization and enhanced charge injection and migration at higher temperatures. Bipolar charges appear in the vicinity of interface in some XLPE/EPDM double layers with silicone grease. This phenomenon can be explained by Maxwell-Wagner polarization at two interfaces of XLPE/silicone grease and EPDM/silicone grease. The addition of silicone grease decreases the conductivity of XLPE/EPDM double layers. Based on the proposed three-component exponential decay model, it is found that the interfacial charge movement affects the polarity of induced relaxation current, and the addition of silicone grease decreases the interface trap depth. [ABSTRACT FROM AUTHOR]

Wearable biosensors are considered to be a promising technology that revolutionizes conventional health monitoring methods as it is able to provide precautions when potential health problem is detected. However, the current fatigue-monitoring methods are still using either invasive blood tests or bulky inconvenient devices. Herein, we present a new skin patch sensor based on porous Ultra-High-Molecular-Weight Polyethylene (UHMWPE) nanomembranes which tracks muscle fatigue through sweat biomarkers, particularly cortisol hormone. By having nano-level thickness (i.e. around 100nm), the sweat sensor is able to conform perfectly to human skin without the necessity of any adhesives. We used Raman spectroscopy to analyze the sweat cortisol in the skin patch, established the calibration curve for both qualitative and quantitative characterization of sweat cortisol level change and validated the measurements with the blood samples collected at the same exercise intensity. From our experimental data, it is concluded that the cortisol level increases as the exercise intensity are increased and a strong correlation between the sweat cortisol and blood cortisol has been proven, demonstrating the patch’s ability to detect sweat cortisol which acts as a strong indicator of sports fatigue level. Our developed UHMWPE membrane opens up a large opportunity for developing a one-of-a-kind sweat sensor by further integrating it with flexible electronics for signal processing and real-time transmission in future work. [ABSTRACT FROM AUTHOR]

In the frame of the effective Container inspection at BORDer control points (C-BORD) project [H2020 program of the European Union (EU)], a Rapidly Relocatable Tagged Neutron Inspection System (RRTNIS) has been developed for a nonintrusive inspection of cargo containers, aiming at explosives and other illicit goods detection. Twenty large-volume NaI detectors are used to determine the elements composing inspected materials from their specific gamma-ray spectra signatures induced by fast neutrons. The RRTNIS inspection is focused on a specific suspect area selected by X-ray radiography. An unfolding algorithm decomposes the energy spectrum of this suspect area on a database of pure element gamma signatures. A classification is then performed between inorganic materials, such as metals, ceramics, or chemicals, and organic materials like wood, fabrics, or plastic goods. Concerning organic materials, the obtained elemental proportions of carbon, nitrogen, and oxygen allow discriminating explosives from illicit drugs and benign substances. This article reports on the final laboratory tests performed at Commissariat à $\text{I}^\prime $ Énergie Atomique et aux Énergies Alternatives (CEA) Saclay, France, to assess the RRTNIS detection performances before further demonstration tests in a real seaport environment. Simulants of explosives and illicit drugs have been hidden at different depths inside iron or wood cargo materials, which are representative of the different neutron and gamma attenuation properties encountered in real cargo containers. Hundreds of experiments have been performed, showing that a few kilograms of explosives or narcotics can be detected by the RRTNIS in 10-min inspections. [ABSTRACT FROM AUTHOR]

To find the optimal shielding design for compact accelerator-driven neutron sources (CANS) using multiobjective optimization, we developed a new method called nondominated sorting genetic algorithm-Monte Carlo method (NSGA-MC). NSGA-MC employs NSGA-II to optimize the shielding parameters based on calculations made by the Monte Carlo N-Particle Transport Code (MCNP). A layered shielding configuration with two materials of borated polyethylene (BPE) and lead (Pb) in the order of BPE/Pb/BPE/Pb for RIKEN Accelerator-driven Compact Neutron Source (RANS) was examined using this method, and two objectives were optimized simultaneously: equivalent dose rate and shielding structure weight. As a result, a tradeoff relationship between the objectives was finally obtained in the form of a Pareto front. The optimization results revealed significant improvements compared with the current RANS shielding configurations in terms of both dose and weight. The results indicate that a reduction in shielding weight of about 60% can be obtained by adopting the optimized shielding structure design, without sacrificing shielding performance. The performance of the method was discussed by showing advantages of NSGA-MC over the so-called weight sum method. [ABSTRACT FROM AUTHOR]

The present work focuses on the effect of water tree development on crystalline structure of low-density polyethylene (LDPE). LDPE samples with 5 mm in thickness are prepared by the hot-pressing method, and then aged by the water-needle method at a voltage of 6 kV/5 kHz. After aging for 250, 500 and 750 hours, the cultivated water trees are observed in the anatomical sections of the samples. In order to study the crystalline structure, differential scanning calorimetry (DSC) and Raman spectroscopy (Raman) are adopted to analyze the LDPE samples with/without water trees. DSC results reveal that the crystallinity decreases with the growth of water tree, and the content of non-crystalline region gradually increases. It is found from Raman results that the appearance of water trees causes the decrease of crystallinity and the increase of interfacial content. As water trees grow, their values keep almost unchanged, but the distributed area with lower crystallinity and higher interfacial content is expanding. For the amorphous content, both the value and spatially distributed character almost remain constant. At last, the results obtained by the two methods are compared, and the effect of water tree growth on the crystalline destruction is discussed. [ABSTRACT FROM AUTHOR]

Density is a very important property of materials because of its influence on their mechanical properties. For this reason, the possibility of measuring material density is of strategic importance for several industrial applications such as wood boards sawing, wood panels production, or ceramic tiles manufacturing. In order to answer to this need, X-ray densitometry techniques and computed tomography (CT) scanners are used nowadays. However, these traditional X-ray inspection techniques usually measure only relative density, or, in other terms, they need a calibration procedure before operation. To overcome this issue, Due2lab s.r.l. in collaboration with the Istituto dei Materiali per l’Elettronica ed il Magnetismo (IMEM)–Consiglio Nazionale delle Ricerche (CNR) Institute developed a CdZnTe (CZT)-based X-ray spectrometer capable of determining the absolute density value of a sample material in terms of g/cm3 (and additionally extracting information about its elemental composition). The system has been specifically designed for in-line real-time nondestructive inspection of industrial production; thus, it is potentially capable to return density information within a very short acquisition time. In this article, we will describe the CZT spectrometer and the hyperspectral X-ray analysis set-up in detail and we will show how to perform absolute density measurement on three different materials: 1) a plastic polyethylene sample, 2) ceramic tiles, and 3) pine and fir wood samples. [ABSTRACT FROM AUTHOR]

Polymers are plastic materials used as insulators in power supplies, pulsers, transformers, etc., because of their low cost and excellent insulating properties. However, in several applications, the insulating performance of these materials is limited by the surface flashover instead of the dielectric bulk breakdown (BD). On the other hand, many works have demonstrated that the material hydrophobicity has a huge effect on the increase of resistance to surface flashover in polymers. In this article, to change this material property, the plasma immersion ion implantation (PIII) technique has been used for the treatment of sample surfaces of two important polymers: ultrahigh molecular weight polyethylene (UHMWPE) and poly-methyl-methacrylate (PMMA) used in medical and industrial applications, respectively. By means of the PIII treatment, it was shown that the surface BD voltage of such polymers has increased, improving the resistance to surface flashover. Contact angle diagnostic and atomic force microscopy (AFM) were measured, respectively, for the surface hydrophobicity and roughness to correlate with the increase of the surface BD voltage. Moreover, a special BD testing pulser is employed to assess the polymer resistance to surface flashover by measuring the corresponding BD voltage under atmospheric pressure. [ABSTRACT FROM AUTHOR]

The insulation around the electrical cabling in nuclear power plants is frequently made of ethylene-propylene rubber and crosslinked polyethylene that is subjected to low levels of environmental stressors and radiation over the duration of their decades long service life. For the purpose of maintenance and reactor recertification, it is necessary to develop a non-destructive approach to determine the degree of damage the insulation has sustained. Accelerated aging experiments are used to develop these methods, although it is unclear how to relate these specimens to in situ aged ones. Here a kinetic rate model is used to investigate the impact of radiation dose rate and total dose on the crosslinking and chain scission of polyethylene. Analytical expressions for the concentration of crosslinking and scission sites as a function of time and dose rate, both during and post irradiation, are presented. During irradiation the concentration of crosslinking sites increases linearly with time, and when the dosing ends the crosslinking reaction terminates. The scission reaction begins slower, due to the necessity of forming intermediate species, but increases in rate, and eventually the concentration of scission sites overtakes crosslinking. However, at low dose rates, less than 10 Gy/hr, scission damage is always the primary form of damage. Unlike the crosslinking reaction, scission continues for months and years due to the slow decomposition of the intermediate species. [ABSTRACT FROM AUTHOR]

MgO/LDPE nanocomposites with various nanofiller loadings are fabricated and the morphology and trap properties are characterized to investigate their effect on DC conductivity and electrical breakdown strength. It is found that DC conductivity depends on both shallow and deep traps. As the nanofiller loading increases, the density of shallow traps increases, leading to higher shallow trap-controlled hopping conductivity, while the deep traps increase firstly due to the formation of isolated interfacial regions and then decreases caused by the overlapping of interfacial regions, resulting in the variation in charge trapping-detrapping dynamics. An equation considers both the shallow trap-controlled hopping and the charge trapping-detrapping processes is derived to calculate the DC conductivity of MgO/LDPE nanocomposites, and the calculation results are consistent with experiments. The DC electrical breakdown strength is influenced by both the morphology and deep trap properties. At low nanofiller loadings, higher crystallinity and smaller crystallite size may block the motion of molecular chains in LDPE nanocomposites, and deep traps formed in interfacial regions hinder the charge transport. The synergetic effects of nano-doping on morphology structure and charge carrier transport enhances the DC electrical breakdown strength of MgO/LDPE nanocomposites. [ABSTRACT FROM AUTHOR]

Polyethylene based nanocomposites have been widely researched for being potential insulating materials in high voltage DC equipment. One of their key properties is the enhanced DC breakdown strength (E b-DC). For a long time, the E b-DC of polyethylene nanocomposites has been attributed to the deep charge traps located at the interphase region between the nanofiller and polymer matrix. In this work, we prepared XLPE/Al(OH) 3 nanocomposites with 0.1 to 3 wt% nano-Al(OH) 3 and studied their E b-DC at 20 to 90 °C. The results show that the XLPE/Al(OH) 3 nanocomposites possess significantly increased E b-DC , although having a large amount of shallow charge traps, and more likely causing homocharge injection. The results of breakdown tests show that E b-DC first increases and then decreases at 20 to 70 °C with increasing nanofiller while it shows a totally opposite trend at 90 °C. E b-DC decreases dramatically with increasing temperature, a crossover phenomenon of E b-DC appears at about 80 °C. The elastic modulus of XLPE/Al(OH)3 at different temperatures was obtained and it shows a similar trend with E b-DC. Therefore, the mechanical properties influenced by morphology and space charge properties modulated by charge trap characteristics were analyzed to jointly determine the E b-DC of XLPE/Al(OH) 3 nanocomposites at different temperatures. [ABSTRACT FROM AUTHOR]

This paper examines the effect of Co60 gamma-ray irradiation to a maximum total dose of 1000 kGy on the charge transport in polyethylene based micro/nanocomposites. Micron sized hexagonal boron nitride (BN) and nano size silica (SiO 2) fillers are used in this work. Surface potential decay measurement are used to evaluate the charge transport in the composite samples. Scanning electron microscopy, Fourier transform infrared spectrum, differential scanning calorimetry, and gel content techniques are used to understand the irradiation induced variations in the microstructure of the composites. The results indicate that the carrier trap center becomes shallower and the carrier mobility tends to increase with increasing gamma ray dose and this effect is mitigated with the addition of fillers. It is suggested that the radiation induced reduction in the crystallinity and the appearance of voids and the formation of carbonyl groups are responsible for the observed effect. The micron- and the nano-size particles hinder the penetration of oxygen, thereby reducing oxidation, and the gamma-ray irradiation induces increased charge transport in the composites. [ABSTRACT FROM AUTHOR]

A blend of high and low density polyethylene was aged at 160 °C in air and the impact of the chosen aging protocol on local chemistry, crystallinity and charge transport dynamics was considered. The aging conditions were chosen in order to exploit oxygen diffusion effects, such that the resulting systems could be considered as bi-layer specimens, containing two regions: a uniform lightly aged layer and a more spatially varying highly aged layer, which vary in the concentrations of aging-related defects such as carbonyl groups and unsaturation. For aging periods up to 3 h, little space charge was found within both the highly and lightly aged layers. However, after aging for about 3.5 h, an abrupt change in behavior was observed, whereby charges move rapidly through the highly aged layer, accumulating at the interface with the lightly aged layer. Sample melting behavior, as determined by differential scanning calorimetry, was found to depend on aging time, as a result of impeded crystallization and retarded reorganization kinetics. We suggest that this abrupt change in charge transport behavior is a consequence of the local concentration of chemically related trapping sites exceeding some critical threshold. The consequence of the resulting space charge distribution is a dramatic increase in the local electric field across the lightly aged layer and a consequent reduction in the overall DC breakdown strength. However, while further aging exacerbates these space charge effects, counter to expectations, the breakdown strength then recovers somewhat, suggesting a change in the underlying mechanism of electrical failure. [ABSTRACT FROM AUTHOR]

Inverse power model (IPM), which is a phenomenological model that can predict the electrical life of crosslinked polyethylene (XLPE) insulation, is commonly used to design the insulation and test voltage of cables. Unfortunately, IPM cannot reflect the physical process of electrical aging, and the parameters have no physical significance, which limits the application range and extrapolation accuracy of IPM. Although the physical models of electrical life based on physical and chemical degradation processes exhibiting high accuracy are available, the equations of physical are complex to be popularized in engineering applications. In this paper, a new physical life model for engineering application is presented based on the relationship between transition-state theory and IPM. The proposed model considers the effects of AC electrical stress and thermal stress on aging. The proposed model is fitted to the life data of AC XLPE cable, thus confirming the validity of the proposed model. [ABSTRACT FROM AUTHOR]

In this work, curcumin nanocrystals (CCN) was used as fluorescence probes for monitoring the accelerated aging of high density polyethylene (HDPE) used in insulation of high-voltage cables. CCN has been synthesized and incorporated into HDPE matrix using hydrothermal process (HydP) at 202.65 kPa and temperatures of 60 °C and 120 °C. The apparent activation energy (EA) for CCN incorporation into HDPE matrix was 54.4 kJ/mol. The resulting nanocomposite HDPE-CCN has been characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and fluorescence spectroscopy (FS). The crystallinity of HDPE and HDPE-CCN determined by DSC were 71.27% and 70.30% respectively, suggesting that the presence of CCN does not modify significantly the microstructure of HDPE. Accelerated aging of HDPE-CCN samples was carried out and the stress to break ($\varepsilon _{\mathrm {b}}$), Young’s modulus (E) and fluorescence intensity (FI) were used as measurements of HDPE degradation. Mechanical properties ($\varepsilon _{\mathrm {b}},\mathrm {E}$) and FI measurements do correlate with age-related material degradation on the HDPE samples examined. [ABSTRACT FROM AUTHOR]

In the present study, the growth and partial discharges properties of DC electrical trees in cross-linked polyethylene (XLPE) were investigated under positive and negative DC voltages. The obtained results revealed that the voltage rise exerted significant influences on growth properties of DC trees. In either polarity, DC electrical trees grew rapidly during rising voltage and maintained the rapid growth for a certain time after DC voltage reached a constant value. The growth rate of positive DC electrical trees was quite faster than that of negative ones, and channel breakdown mainly occurred in positive ones. Although the growth rates of positive and negative DC electrical trees were different, their shapes were similar (both were branch-like electrical trees with one or two main branches). Self-healing usually occurred in negative DC electrical trees, thus electrical tree branches gradually disappeared under the application of steady DC voltage or when the voltage was off. Partial discharges mainly occurred at the beginning of electrical tree growth; however, the amount of partial discharge was relatively small, and it gradually reduced even during the rapid growth of electrical trees, consequently, almost no partial discharges were found when the voltage was constant. Finally, a discharge-avalanche theory was proposed to explain the growth properties of DC electrical trees. [ABSTRACT FROM AUTHOR]

Samples of polypropylene and high density polyethylene have been exposed to partial discharge activity at elevated temperatures under the influence of combined AC and DC stresses in the range of 1 and 2.5 kHz. Based on FTIR-ATR and dielectric spectroscopy data values for the carbonyl index (CI), the low frequency conductivity (σ 0) and a proposed new index the susceptibility index (χI) have been calculated to characterize the degree of ageing in the samples. The susceptibility index reflects changes in the number of dipoles and the distribution of dipole moments in the system as a result of ageing. The rate of energy delivery from the partial discharge activity has also been calculated and has been found to be dependent on the frequency of the AC component of the stress. Strong correlations are observed between the behavior of the individual indices and the rate of energy delivery. Possible reasons for these observed correlations are discussed and the observed differences in the behavior of the ageing under different experimental conditions are considered. [ABSTRACT FROM AUTHOR]

In this work, the thermal pyrolysis process and produced chemical defects of crystalline polyethylene, taking the effects of oxygen into account, are explored by molecular dynamics simulation based on ReaxFF force field. The trap energies and sites of various types of chemical defects are calculated by density function theory (DFT), in which hybrid functional XC HSE06 is adopted. The results indicate that double bond C=C, conjugate double bond C=C-C=C, C=C=C and carbonyl C=O are the main products during thermal aging, and these defects are easier to formed at the breaking points of carbon backbone, which is different from the geometries generally used in the previous DFT computations. For electrons, chemical defects C=O and C-C=C-C at breaking points (BP) produce relative deep traps 1.810 and 1.054 eV, and C=C at BP shows shallower traps with energy of 0.445 eV. For holes, C=C-C=C at BP and C=C in the backbone generate deep traps 1.614 and 1.119 eV, and C=C at BP presents shallower traps with energy of 0.689 eV. [ABSTRACT FROM AUTHOR]

The current work investigates the effects of filler calcination on the structure and dielectric properties of polyethylene/zirconia (ZrO 2) nanocomposites. Calcination temperatures of 600 and 900 °C have been applied to ZrO 2 in an attempt to modify its surface chemistry and structure. Calcination results in a slight reduction in the concentration of physically adsorbed water on ZrO 2 and, in addition, structural reorganization of the ZrO 2 nanopowder. Consequently, the real permittivity of nanocomposites containing calcined ZrO 2 is reduced compared to nanocomposites containing uncalcined ZrO 2. Furthermore, the DC breakdown strength of nanocomposites containing calcined ZrO 2 improves compared to nanocomposites containing uncalcined ZrO 2. Since the removed water content is minimal, we primarily attribute the observed dielectric results to structural changes in ZrO 2 rather than water-related effects. As such, calcining can have positive effects in enhancing the dielectric properties of ZrO 2 -based nanocomposites. [ABSTRACT FROM AUTHOR]

Soft and integrated design can enable wearable haptic devices to augment natural human taction. This paper proposes a novel, soft, haptic finger-worn wearable device based on compliant and adhesive silicone skin and lightweight twisted and coiled polymer (TCP) actuators using ultra high molecular weight polyethylene (UHMWPE) fibers to provide lateral skin stretch sensations. Recently, silicone elastomers have been used in wearable sensors and in haptic applications for their high compliance or adhesion. TCP actuators have also demonstrated high power to weight ratios, large stroke length, simple mechanism, and inherent softness. Lateral skin stretch is sensitive to small motions and has been used for intuitive proprioceptive feedback applications. We combined these characteristics to design and manufacture a wearable, functional haptic prototype. Prototype performance was evaluated using an optical tracking system, a force gauge test bench, and compared to vibrotactile haptic feedback in a experiment with 14 healthy participants. Results showed that participant mean reaction times were comparable to those of a vibrotactile feedback system, though task completion times were longer. This paper is the first to employ TCP actuators for haptic stimulation and could serve as a foundation for future applications involving soft wearable haptics in gaming, health, and virtual reality. [ABSTRACT FROM AUTHOR]

There are various models for describing the charge transport in polymers but it is unclear how to choose the appropriate one for a given system. In this study, we determine the relevant charge transfer model for several insulating polymers by evaluating the Marcus parameters for electron and hole transfer with the aid of first-principles calculations. As expected, except for electron transfer in polyethylene and isotactic polypropylene, non-adiabatic (polaron) hopping takes place in most polymers, owing to the small inter-chain electronic interactions (10–100 meV) and large polaron formation energy (100–1000 meV). Therefore, the first-principles based parameter-free, multi-scale modeling approach, which we developed for evaluating the hole transfer property in polyethylene, can be used to study the electronic carrier transport properties in wide variety of polymers. The computed Marcus parameters imply that the electron and hole mobilities in syndiotactic polystyrene and polytetrafluoroethylene are larger than the hole mobility in polyethylene and isotactic polypropylene, which agrees with experimental data. The strong chain-length dependence of the computed Marcus parameters indicates that slight change in the polymer structure can result in significant variations in the charge mobility. [ABSTRACT FROM AUTHOR]

Two polyethylene and two polypropylene blends crystallized under non-isothermal conditions were compared to a crosslinked polyethylene (XLPE) reference material. Selected blends contained a gelation agent, which forms a network structure within the material. Compared to XLPE, the blends offered higher melting points, reduced electrical conductivity, increased electrical breakdown strength, improved space charge performance and enhanced thermo-mechanical stability. Additional improvements in space charge behavior were also noted in systems containing the DBS gelation agent. The ability to provide recyclable insulation materials capable of operating at much higher temperatures than XLPE, combined with enhanced dielectric properties, may prove advantageous to cable manufacturers, particularly in renewable energy applications. [ABSTRACT FROM AUTHOR]

This paper presents investigations on a usage of graphene as a voltage stabilizer for polyethylene blends in the potential recyclable high voltage direct current (HVDC) cable insulation. Thermal and electrical properties of the blends with/without graphene were evaluated by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), electrical treeing tests, DC conductivity and space charge measurements. Trap energy distributions in the blends were estimated using the measured space charge decay data. The obtained results show that additive-like amounts of graphene can improve the thermal stability of the polyethylene blends. The influence of the graphene on the tree inception voltage (TIV) of the polyethylene blends is not significant, whereas the low density polyethylene/high density polyethylene (LDPE/HDPE) with/without graphene demonstrates the highest TIV comparing to the LDPE, LDPE/polypropylene, and their corresponding graphene added materials. It is found that the DC conductivity of the polyethylene blends with/without graphene increases consistently with the increase of the temperature. The conductivity of the LDPE/HDPE decreases apparently with the inclusion of graphene. It has been shown that space charge accumulations can be suppressed by the addition of graphene in the polyethylene blends. It is postulated that the high trap level and trap energy density of the polyethylene blends with graphene are closely connected to the suppression of the space charge accumulation in the blends. [ABSTRACT FROM AUTHOR]

In high voltage direct current (HVDC) power transmission systems, electrical equipment at the valve side usually withstands complex stresses like AC-DC combined voltages. Understanding the charge migration and accumulation characteristics under complex stresses and their influences on the breakdown strength are of great significance. This paper presents an in-depth simulation study on the AC-DC combined breakdown strength using a modified bipolar charge transport model, which takes the deterioration of materials into consideration. Firstly, the simulation results of charge profiles under AC voltages agree well with experimental results, which partly illustrates the appropriate selection of parameters. Then the AC breakdown strengths with different ramping rates and frequencies are studied. Charges accumulated relatively close to the surface of samples can cause severe distortion of the electric field after the change of voltage polarity. After that, the breakdown voltages with different ratios of the AC to DC component are calculated and analyzed, especially on how AC and DC component influence the charge migration and accumulation during the evolution of the aging process eventually leading to breakdown. The simulation results of AC-DC combined breakdown voltages show good agreement with previous experimental results. [ABSTRACT FROM AUTHOR]

Thermoplastic blending material is considered as a recyclable environmental-friendly potential candidate for future direct current (DC) cable insulation. Although such a non-crosslinking material has been proved to be superior in certain properties compared with cross-linked polyethylene (XLPE), one of the central concerns for the application of this material system lies in its DC performance at high temperature. In this paper, we investigate the DC conductivity and breakdown strength of a thermoplastic linear low-density polyethylene (LLDPE)/high-density polyethylene (HDPE) blending material under temperature range from 30 to 90°C, the results show that this blend exhibits better temperature-stability in DC performance, and it shows lower conductivity and higher breakdown strength compared with XLPE. The crystalline structure is studied through X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the LLDPE/HDPE blend exhibits a co-crystalline structure with higher crystallinity and larger microcrystal, and when temperature rising, crystallinity and microcrystal size of blend decreases slower compared with XLPE. Such results might enable further application of the LLDPE/HDPE blend on DC cable insulation. [ABSTRACT FROM AUTHOR]

Dielectric response analysis is one approach for the condition assessment of high voltage insulation systems, and measurement of the dissipation factor or tan δ is widely used in practice. This article presents an experimental study of DF measurement over the frequency range from 1 mHz to 50 Hz. Three different short sections of service-aged 11-kV cross-linked polyethylene cable are used as test specimens. Low-voltage polarisation / depolarisation current and frequency domain spectroscopy techniques are employed in the investigation. Following the experimental work, numerical analysis is carried out utilizing the Davidson-Cole (D-C) model. To optimize the final parameters of the model, numerical simulation is performed using 3 or 4 R-C branches with different values of Jonscher and D-C constants. It is shown that results from numerical simulation agree well with the experimental results over the tested frequency range. [ABSTRACT FROM AUTHOR]

Chemical impurities in dielectric materials are one of the reasons that reduce the height of charge injection barrier. These impurities create energy states in dielectric band gap, which impact on the injection process. Chemical impurities that are studied in this paper include carbonyl, vinyl, and conjugated double bond impurities. These types of chemical impurities are the most common in technical dielectric polymers such as polyethylene. These impurities are studied using the computational quantum mechanics in the scope of density functional theory (DFT). The computed barrier in the present work is carried out using a new technique based on correcting the underestimation in polyethylene band gap due to the DFT computations. It is found that terminal carbonyl and conjugated double bond produce the lowest injection barrier for electrons and holes, respectively. The depth of these impurity states are compared with that developed in bulk PE and at the interface with other metals. The similarity in calculated barrier for electrons and holes is in agreement with the experimental observations. This paper concludes that chemical impurities cannot alone explain the activation energy of conduction of 1 eV. [ABSTRACT FROM AUTHOR]

Microwave and millimeter-wave reflectometry, a form of continuous-wave surface penetrating radar, is an emerging nondestructive inspection technique that is suitable for nonmetallic pipelines. This paper shows a $K$ -band microwave reflectometry instrument implemented onto an in-line pipe-crawling robot, which raster-scanned cracks and external wall loss on a high-density polyethylene (HDPE) pipe of diameter 150 mm and wall thickness 9.8 mm. The pipe was scanned with three environments surrounding the pipe that approximated the use cases of overground HDPE pipelines, plastic-lined metal pipes, and undersea HDPE pipelines. The instrument was most sensitive when cracks were oriented parallel to its magnetic (H) plane. Any small variation in the standoff distance between the instrument’s probe antenna and the pipe wall, which was not easy to avoid, was found to obscure the image. To mitigate this problem, a sensitivity analysis showed that an optimal frequency can be chosen at which standoff distance can vary by up to ±0.75 mm within a certain range without distorting the indications of defects on the image. [ABSTRACT FROM AUTHOR]

The characterization of an atmospheric pressure microwave argon plasma in the form of a plasma sheet and the results of its use in the investigation of the wettability modification of polyethylene (PE) surfaces are presented in this paper. The spectroscopic investigations performed indicate a plasma temperature at the level of 750–1100 K and an electron density at the level of 2.9– $5.4\times 10^{14}$ cm−3. The following PE-type specially prepared materials were subjected to the plasma treatment process: PE (pure low-density PE), PE + UV (PE with a UV stabilizer), PE − UV + M (with a UV stabilizer and a montmorillonite), PE + S (PE with soot), and PE − F (PE with a UV stabilizer, a montmorillonite, and soot). The experimental investigations prove the high potential of the presented method for the PE surface activation in industrial applications. The atomic force microscopy scanning of samples was performed before and after the plasma treatment. The aging of the adhesion enhancement effect indicates that the water contact angle is related to the surface energy changes. [ABSTRACT FROM AUTHOR]

The surface of 180- $\mu \text{m}$ polyethylene (PE) and 200-nm polytetrafluoroethylene (PTFE) powders are hydrophilized by using surface dielectric barrier discharge (sDBD) applied to a batch of 20 g for both cases. On the sDBD electrode, charged particles by plasma generation are able to diffuse onto the power surface through small voids. In order to know the level of hydrophilic treatment on the powder, absorption tests by using droplet was carried out. This principle is based on the fact that the inner gap between powders are small enough that a liquid with a certain surface tension is absorbed or formed on powder layer when dropped on the powder surface. The minimum isopropyl alcohol (IPA) concentration absorbed into the powder was measured by an aqueous solution with a mixture of IPA and D.I water. By lowering the IPA concentration, improvements in the hydrophilicity were obtained. The concentration of IPA before treatment of PE powder was 15% and decreased to 3% after treatment. In the case of PTFE, IPA concentration decreased slightly from 39% to 30% after the treatment. Also, the surface treated PE and PTFE displays a significant difference in the degree of dispersion in water and n-methyl pyrollidone solvent. In the field-emission scanning electron microscope analysis, the morphology of the treated surface was clean. From composition of the surface by X-ray photoelectron spectroscopy, when the untreated sample is 100% C–H, the plasma treated PE shows 82.48% C–H, and 17.52% C–O. A partial change in the C–F bond is shown for PTFE. [ABSTRACT FROM AUTHOR]

This paper reports on an investigation of the effects of calcination on the structure and dielectric properties of polyethylene/silica (SiO 2) nanocomposites. Calcination temperatures of 600 and 900 °C have been used in order to modify the surface chemistry and surface structure of the SiO 2. The results show that, after calcination, the concentration of surface hydroxyl groups and water molecules around SiO 2 and within resulting nanocomposites is reduced. The real permittivity of nanocomposites containing calcined SiO 2 decreases compared to nanocomposites based on uncalcined SiO 2. The DC breakdown strength of nanocomposites containing calcined SiO 2 becomes higher than those containing uncalcined SiO 2. In contrast, AC breakdown was found not to be significantly affected by addition of any of the silicas considered here. The use of calcined nanofillers can have positive effects akin to the use of chemically functionalized nanofillers in enhancing the dielectric properties of nanocomposites; both approaches remove polar surface hydroxyl groups. [ABSTRACT FROM AUTHOR]

Triboelectric charging is used in many applications including electricity nanogeneration, safety or electrostatic separation of insulating materials. Insulating granules charge must be the highest in electrostatic separators so that the electric field forces allow their separation. Dielectric barrier discharge (DBD), used for ozone production, depollution or surface treatment, is able to change the triboelectric properties of insulating materials. The aim of this study is to improve the triboelectric charging of polyethylene particles by exposing them to an atmospheric DBD. Signal shape, exposure duration, voltage amplitude, and frequency, which rule the DBD, are studied. After exposing the particles to DBD, they are charged in a vibratory device during 5 min. Then, particles are put in a Faraday pail connected to an electrostatic voltmeter to measure the acquired charge. Results show that the square waveform has the best effect and that the duration of the DBD treatment should not exceed 10 s, for the amplitude of the applied voltage of 21 kV. [ABSTRACT FROM AUTHOR]

This article demystifies manhole explosions by exploring the complex interactions between electrical cables and chemistry inside and adjacent to manholes. [ABSTRACT FROM AUTHOR]

Barriers to charge injection at polymer/metal interface is key to understanding high field conduction in cables and capacitors. The present paper investigates barriers to charge injection at the interface of copper and polyethylene (PE), one of the most dominant material combination in the power industry, with a focus on morphological deformation. Using computational quantum mechanics in the framework of density functional theory (DFT) barriers to charge injection where calculated showing similar results to previous DFT studies on the interface of Pt, Au, and Ag in terms of the absolute barriers to hole and electron injection. However, states appearing between the Fermi level of Cu and the conduction band of PE where identified leading to the lowering of the barrier to electron injection by about 0.9 eV. These states were due to the morphological deformation that takes place for both the metal and the polymer at the interface. No similar states were identified in the case of Pt, Au and Ag in similar studies. The paper stresses on the importance of considering morphological deformation in lowering the barriers to charge injection in soft metal which is less considered as compared to chemical impurities. [ABSTRACT FROM AUTHOR]