Влияние содержания технического углерода на температурные зависимости электропроводности полимерного композита

It was found that in the region of the percolation threshold, depending on the dominance of one or another conduction mechanism, the temperature dependence of the specific volume resistivity ρ(Т) of the polymer composite based on a matrix of ethylene vinyl acetate is significantly transformed. With an increase in the CB content, there is a decrease by several orders of magnitude in the maximum value of the relative resistivity ρ(Т)max/ρ20 in its temperature dependence. Peroxide crosslinking of matrix macromolecules leads to a change in the nature of the temperature dependence of resistivity.

Towards a Kinetic Modeling of the Changes in the Electrical Properties of Cable Insulation during Radio-Thermal Ageing in Nuclear Power Plants. Application to Silane-Crosslinked Polyethylene

The radio-thermal ageing of silane-crosslinked polyethylene (Si-XLPE) was studied in air under different dose rates (6.0, 8.5, 77.8, and 400 Gy·h−1) at different temperatures (21, 47, and 86 °C). The changes in the physico-chemical and electrical properties of Si-XLPE throughout its exposure were determined using Fourier transform infrared spectroscopy coupled with chemical gas derivatization, hydrostatic weighing, differential scanning calorimetry, dielectric spectroscopy and current measurements under an applied electric field. From a careful analysis of the oxidation products, it was confirmed that ketones are the main oxidation products in Si-XLPE. The analytical kinetic model for radio-thermal oxidation was thus completed with relatively simple structure-property relationships in order to additionally predict the increase in density induced by oxidation, and the adverse changes in two electrical properties of Si-XLPE: the dielectric constant ε’ and volume resistivity R. After having shown the reliability of these new kinetic developments, the lifetime of Si-XLPE was determined using a dielectric end-of-life criterion deduced from a literature compilation on the changes in R with ε’ for common polymers. The corresponding lifetime was found to be at least two times longer than the lifetime previously determined with the conventional end-of-life criterion, i.e., the mechanical type, thus confirming the previous literature studies that had shown that fracture properties degrade faster than electrical properties.

A new generation of cable grade poly(vinyl chloride) containing heavy metal free modifier

Many additives are used to improve the performance of cables in terms of increasing their flame retardancy, thermal stability, thermal conductivity, and other characteristics. Unfortunately, most of these additives contain heavy metals. Therefore, the main objective of this study is to introduce a material representing a new generation of environmentally friendly heavy metal-free stabilizers for cable grade poly(vinyl chloride) that can compete with traditional materials in terms of performance and distinctive properties. This unique additive is Oxydtron, a synthetic silicate or simply nanocement. The tests performed are rheological properties represented by a capillary rheometry analysis, limiting oxygen index, and volume resistivity. The most significant improvement in Bagley correction measurements was 14.61%; 18.13%; and 27.20% more than poly(vinyl chloride) basic formulation when using 5wt.% Oxydtron at 160 °C, 170 °C, and 180 °C, respectively. Also, the mean increases in relaxation time were 3.200 times, 8.825 times, and 12.458 times more than poly(vinyl chloride) basic formulation with 1wt.%, 3wt.%, and 5wt.% of Oxydtron, respectively. Furthermore, the Oxydtron lowered the value of the accompanying thermal gradient of the L.O.I test, reducing the heat-affected zone. The best result was with the extrusion processing method due to the uniformity of the processing conditions. However, the thermal gradient analysis showed residual heat stress in the test samples after cutting the burning layer and re-testing the samples again; this causes them to burn faster. This situation requires caution for designs that are exposed to high temperatures without burning. The optimum improvement in volume resistivity value was 14.71% and 38.24% more than poly(vinyl chloride) basic formulation after adding 5wt.% and 7wt.% of Oxydtron, respectively.

FFF 3D Printing in Electronic Applications: Dielectric and Thermal Properties of Selected Polymers

The present study is a focused and comprehensive analysis of the dielectric and thermal properties of twenty-four 3D printed polymers suitable for fused filament fabrication (FFF) in electronic applications. The selected polymers include various thermoplastic elastomers, such as thermoplastics based on polycarbonate (PC), polyethylene terephthalate glycol (PETG), and acrylonitrile butadiene styrene (ABS-T). Their overall thermal behavior, including oxidation stability, glass transition, and melting temperature, was explored using simultaneous thermal analysis (STA) and differential scanning calorimetry (DSC). Considering their intended usage in electronic applications, the dielectric strength (Ep) and surface/volume resistivity (ρs/ρv) were comprehensively tested according to IEC 60243-1 and IEC 62631-3, respectively. The values of the dielectric constant (ε’) and loss factor (ε”) were also determined by broadband dielectric spectroscopy (BDS). While, on the one hand, exceptional dielectric properties were observed for some thermoplastic elastomers, the materials based on PCs, on the other hand, stood out from the others due to their high oxidation stability and above average dielectric properties. The low-cost materials based on PETG or ABS-T did not achieve thermal properties similar to those of the other tested polymers; nevertheless, considering the very reasonable price of these polymers, the obtained dielectric properties are promising for undemanding electronic applications.

A Novel Branched Al2O3/Silicon Rubber Composite with Improved Thermal Conductivity and Excellent Electrical Insulation Performance

In this paper, we report a thermal conductive polymer composite that consists of silicone rubber (SR) and branched Al2O3 (B-Al2O3). Owing to the unique two-dimensional branched structure, B-Al2O3 particles form a continuous three-dimensional network structure by overlapping each other in the matrix, serving as a continuous heat conductive pathway. As a result, the polymer composite with a 70 wt% filler achieves a maximum thermal conductivity of 1.242 Wm−1 K−1, which is equivalent to a significant enhancement of 521% compared to that of a pure matrix. In addition, the composite maintains a high volume resistivity of 7.94 × 1014 Ω·cm with the loading of 70 wt%, indicating that it meets the requirements in the field of electrical insulation. Moreover, B-Al2O3 fillers are well dispersed (no large agglomerates) and form a strong interfacial adhesion with the matrix. Therefore, the thermal decomposition temperature, residual mass, tensile strength, modulus and modulus of toughness of composites are significantly improved simultaneously. This strategy provides new insights for the design of high-performance polymer composites with potential application in advanced thermal management in modern electronics.

Performance Analysis Of Electrical Properties Of Resin Transfer Molded Banana Leaf Reinforced Polymer Composites

An investigation of the electrical characteristics of banana leaf reinforced Polymer composites made by resin transfer molding (RTM) has been carried out, with special emphasis on the effects of fibre loading, frequency and temperature. Every parameter, including the dielectric constant (ɛ0), dissipation factor (tan δ), loss factor (ɛ00), and conductivity, increases with increasing fibre concentration over the whole frequency range. A minimum fibre content of 50 % is required for composites to achieve excellent performance values. This increase is large at low frequencies, minimal at middle frequencies, and negligible at extremely high frequencies, according to the results of the study. At low frequencies, the volume resistivity fluctuates in response to fibre loading, while at high frequencies, the resistivity blends together. When the temperature rises, the dielectric constant values rise as well, however once the glass transition temperature is reached, the dielectric constant values fall. This fluctuates depending on the amount of fibre present. Finally, an attempt is made to establish a relationship between the experimental value of the dielectric constant and theoretical expectations.

Novle layered boron nitride nanosheets/cellulose nanofibers/epoxy composite with high thermal conductivity

Studies have shown that the construction of a three-dimensional interconnected filler network is an effective method to improve the thermal conductivity of the through-plane under a lower filler load. However, huge challenges still exist in building a long-range layered filler network and reducing the thermal resistance resulting from contact between fillers and matrix. In this work, boron nitride nanosheets (BNNSs) were proposed to be connected with modified cellulose nanofibers (CNFs) to obtain a long-range layered structure filler skeleton by bidirectional freezing orientation. Then epoxy resin was dipped under vacuum condition to prepare composite with thermal conductivity up to 1.43 W/mK in through-plane when filler content is 4.3 vol%, and the composite had low thermal expansion coefficient of 64.1 ppm/°C and excellent volume resistivity up to 3.7 × 1012 Ω cm at the same time.

Electro mechanical properties changes of LDPE doped with industrial type MgO for cable insulation purposes

<p>This manuscript introduces the changes of a comprehensive electromechanical properties bundle for low density polyethylene compounded to microscale magnesia (LDPE/MgO) to obtain electrical cables insulating material. Composites of various filler loading weight ratios were prepared by melt intercalation technique; multiple samples were produced in sets as they were cut with definite dimensions as per recommendations of the related testing standard then electrically and mechanically examined following the instruction dictated by the code while preserving typical test condition for all sets. Dielectric strength, volume resistivity, capacitance, and loss angle were the tests of the electrical test pack, while elongation, tensile strength, and melt flow rate were the mechanical and rheological tests applied. Test’s findings were compared to each other’s and to the base material to identify the differentiation. Electrical test results show improvements in the composite features at low loading percentages, whereas the mechanical tests revealed a deterioration in the mechanical properties along with all ratios under investigation. The research aims to determine the compositing benefit extents and drawbacks when a conventional compounding method and inexpensive filler are used, incurring marginal cost impact.</p>

Flame Retardancy and Excellent Electrical Insulation Performance of RTV Silicone Rubber

Room temperature vulcanized (RTV) silicone rubber filled with aluminum trihydrate (ATH) is substantially engaged in electrical outdoor insulation applications. The pristine silicone rubber is highly combustible. ATH filled silicone rubber offers excellent electrical insulation but lacks in providing adequate flame retardancy. This short communication reports the novel results on improved flame retardancy of pristine and ATH filled silicone rubber whilst retaining the electrical insulation properties to a great extent. Results suggest that the presence of only one percent of graphene nanoplatelets with ATH sharply reduces the heat release rate and rate of smoke release. A minor reduction in dielectric breakdown strength and volume resistivity is noticed. Furthermore, permittivity and dielectric loss at power frequency suggest that a marginal 1% concentration of nanoplatelet with ATH is an excellent approach to fabricate flame retardant silicone rubber with an acceptable electrical insulation level.

A Facile Method Combined with Acetic Acid Modification and Electroless Plating to Fabricate Copper-plated Nylon 12 Powder for Antistatic Coating

Metal particle could deposited on Nylon 12 (PA12) surface using electroless plating with excellent interface and distribution, but the use of noble metal as catalytic site would increase the process cost and restrict its application. In this work, we employed a facile technology combined with acetic acid etching and electroless copper plating to prepare Cu/PA12 composite powder, and it used as conductive filler for antistatic coating was also studied. Results manifested defects (hole and amorphous structure) and amide group established on etched PA12 surface, which would facilitate the destruction of the [Cu-EDTA] structure, and then the reduction of REDOX barrier. As a result, Cu and Cu2O particles deposited on its surface. The downward trend of volume resistivity of antistatic coating appeared the rule of slow-fast-slow. The lowest volume resistivity was about 105 ohm�cm. This means that the dependable technology has great potential application in preparing metal/polymer composite material at a low cost.