scholarly journals Improved DC Dielectric Performance of -MAH/iPP/SEBS Composite with Chemical Graft Modification

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1094 ◽  
Author(s):  
Yu Zhou ◽  
Jiaming Yang ◽  
Hong Zhao ◽  
Weifeng Sun ◽  
Mingze Gao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dielectric Properties ◽  
Space Charge ◽  
Carrier Transport ◽  
Charge Trapping ◽  
Structure Characterization ◽  
Characterization Methods ◽  
Deep Traps ◽  
Dielectric Performance ◽  
Stimulation Current

In order to achieve both high toughness and favorable dielectric properties of polypropylene materials, a styrene–butadiene–styrene block copolymer (SEBS) was employed as a toughening filler, in addition to a copolymerized polypropylene grafted by maleic anhydride (cPP-g-MAH) as a compatibilization modifier, to develop a novel isotactic polypropylene (iPP) composite (cPP-g-MAH/iPP/SEBS composite) with significantly improved direct-current (DC) dielectric performance and tenacity. The underlying physical and chemical mechanisms of modifying electric insulation were studied utilizing micro-structure characterization methods in combination with multiple thermal–mechanic–electric tests. The SEBS phase islands are uniformly distributed in the PP matrix with evidently improved dispersion due to cPP-g-MAH compatibilization. Compared with iPP, the elastic modulus of cPP-g-MAH/iPP/SEBS composites can be reduced by 58% with doubled thermal elongation, which is still superior to that of cross-linked polyethylene (XLPE), implying that the composites are qualified in terms of mechanical properties for use as power cables. The space charge accumulation and electric conduction are considerably suppressed in comparison with pure iPP and the iPP/SEBS composite. In the interest of charge-trapping characteristics modified by chemically grafting MAH, the deep traps introduced into polypropylene by grafting MAH were measured with a thermal stimulation current experiment to be 1.2 and 1.6 eV of energy level in trapping depth, verified through the first-principles electronic structure calculations with an all-electron numerical orbital scheme. It was concluded that the acquired high density of deep traps can effectively restrict the carrier transport and suppress the injection of space charge, resulting in a remarkable improvement of DC dielectric properties for the MAH grafted composites. The present work demonstrates that the cPP-g-MAH/iPP/SEBS composites are eligible to be applied to polypropylene-based high-voltage DC cables due to their excellent DC insulation performance, together with the appropriate mechanical properties.

Effects of Precursor Infiltration and Pyrolysis Cycles on Properties of Hollow Silica Fiber Reinforced Nitride Composites

2013 ◽  
Vol 328 ◽  
pp. 836-840
Author(s):  
Xiao Rong Zou ◽  
Chang Rui Zhang ◽  
Si Qing Wang ◽  
Hui Zhu ◽  
Cheng An Tao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dielectric Properties ◽  
Silica Fiber ◽  
Low Dielectric Constant ◽  
Fiber Reinforced ◽  
Hollow Silica ◽  
Low Dielectric ◽  
Silica Fibers ◽  
Dielectric Performance ◽  
Calculation Results

2.5-Dimension hollow silica fiber reinforced nitride (2.5D HSFRN) composites were fabricated by repeated infiltration and pyrolysis from hybrid polyborosilazane precursor. The effects of precursor infiltration and pyrolysis (PIP) cycles on densification behavior, mechanical properties, dielectric properties, and microstructures of the composites were investigated. With increasing PIP cycles, the density of 2.5D HSFRN composites increases, the mechanical properties increase accordingly, however, the dielectric properties decrease. The composites prepared after three PIP cycles, which have moderate flexural strength of 77.4MPa and elastic modulus of 20.7GPa, low dielectric constant of 2.98 and loss angle tangent of 3.9×10-3, exhibit suitable mechanical and dielectric properties. The calculation results of dielectric performance show that 2.5D HSFRN composites have good broadband wave-transparent properties, which result from high purity hollow silica fibers with excellent dielectric properties and low density nitride matrix.

scholarly journals Improved DC Dielectric Performance of Photon-Initiated Crosslinking Polyethylene with TMPTMA Auxiliary Agent

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3540 ◽  
Author(s):  
Peng Qiu ◽  
Jun-Qi Chen ◽  
Wei-Feng Sun ◽  
Hong Zhao
Keyword(s):  
Space Charge ◽  
First Principles ◽  
First Principles Calculations ◽  
Charge Accumulation ◽  
Depolarization Current ◽  
Trapping Mechanism ◽  
Crosslinking Process ◽  
Deep Traps ◽  
Molecular Group ◽  
Dielectric Performance

To achieve high direct current (DC) dielectric performance of crosslinked polyethylene (XLPE) applied for insulated cable, the auxiliary crosslinking agent of trimethylolpropane trimethacrylate (TMPTMA) is employed in photon-initiated crosslinking process to the present polar-molecular group which will introduce deep traps for charge carriers. The space-charge accumulation and electrical conductance of XLPE are observably suppressed due to the deep traps deriving from the TMPTMA crosslinkers that are chemically connecting (grafted onto) polyethylene molecules. Thermally stimulated depolarization current tests and first-principles calculations consistently demonstrate a trapping mechanism of impeding charge injection and carrier transport in XLPE with TMPTMA crosslinkers. The characteristic cyclic anhydrides with coupled carbonyl groups are used as auxiliary crosslinkers to promote crosslinking efficiency and provide polar groups to polyethylene molecules which can be effectively fulfilled in industrial cable production. The results of infrared spectroscopy show that the auxiliary crosslinkers have been successfully grated to polyethylene molecules through the UV-initiation process. The space-charge characteristics achieve a significant improvement consistent with the theoretical estimation that deeper electronic traps can be introduced by auxiliary crosslinker and will consequently suppress space-charge accumulation through a trapping mechanism. Meanwhile, the conductivity of XLPE observably increases after using TMPTMA auxiliary crosslinkers at various temperatures of cable operation. The first-principles calculations also demonstrate that substantial electronic bound states have been introduced at the band edge of polyethylene molecules crosslinked by TMPTMA, leading to reduction in electrical conductivity. On the advantage of ameliorating DC dielectric performance by way of UV-initiated crosslinking process, the present research suggests a substantial strategy in XLPE cable industrial productions.

scholarly journals Practical Notes on the Measurement and Interpretation of Thermally Stimulated Discharge Currents in Biaxially Oriented Polypropylene

2019 ◽  
pp. 64-69
Author(s):  
Ilkka Rytöluoto ◽  
Minna Niittymäki ◽  
Kari Lahti
Keyword(s):  
Glass Transition ◽  
Dielectric Properties ◽  
Space Charge ◽  
High Field ◽  
Short Term ◽  
Depolarization Current ◽  
Deep Traps ◽  
Biaxially Oriented Polypropylene ◽  
Oriented Polypropylene ◽  
Thermally Stimulated Depolarization

The measurement and interpretation of high-field thermally stimulated depolarization current (TSDC) of capacitor-grade biaxially oriented polypropylene (BOPP) films are investigated in order to facilitate the derivation of trap parameters. Two main relaxations associable with the glass transition and detrapping of space charge from deep traps are observed, and their dependence on the polarization/depolarization conditions are studied. The complex bipolar nature of the space charge relaxation makes the derivation of trap parameters challenging. Lastly, a brief attempt is made to correlate the TSDC features with morphology and other short-term dielectric properties.

scholarly journals Effects of Interfacial Charge on the DC Dielectric Properties of Nanocomposites

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Jiaming Yang ◽  
Congji Liu ◽  
Changji Zheng ◽  
Hong Zhao ◽  
Xuan Wang ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Breakdown Strength ◽  
Interface Layer ◽  
Low Density Polyethylene ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Effects ◽  
Dielectric Performance ◽  
Positive Effect ◽  
Interfacial Charge

The interfacial charge phenomenon of MgO/low-density polyethylene (LDPE) and SiO2/LDPE nanocomposites was measured by synchrotron radiation small-angle X-ray scattering. Based on the Porod theory, the Porod curve of SiO2/LDPE nanocomposite shows negative divergence but the LDPE and MgO/LDPE do not, which reveals that interfacial charge may exist in the SiO2/LDPE nanocomposite. The DC dielectric properties of the nanocomposites are closely related to the interfacial charge. Experimental results show that the SiO2/LDPE nanocomposite has lower DC conductivity, less space charge, and higher DC breakdown strength than the MgO/LDPE nanocomposite. It is thought that the interfacial charge has a positive effect on the DC dielectric performance of nanocomposites, and the mechanism could be attributed to the scattering effects of the interfacial charge on the carrier migration. There is no obvious interfacial charge in the MgO/LDPE nanocomposite, but it still has excellent DC dielectric properties compared with LDPE, which indicates that the interfacial charge is not the only factor affecting the dielectric properties; the dipole interface layer and the reduction of free volume can also inhibit the migration of carriers and decrease electrons free path, improving the dielectric performance.

Space Charge Simulation of Electric Tree Before Germination in XLPE at DC Voltage Based on Improved Bipolar Carrier Transport Model

2021 ◽  
Author(s):  
Shiyou Wu ◽  
Shusheng Zheng ◽  
Aixu Zhong ◽  
Zongheng Zhang ◽  
Renjie Cao ◽  
...  
Keyword(s):  
Space Charge ◽  
Carrier Transport ◽  
Transport Model ◽  
Dc Voltage

Synthesis and characterizations of metal ions doped barium strontium titanate (BST) nanomaterials for photocatalytic and electrical applications: A mini review

2021 ◽  
Vol 112 (8) ◽  
pp. 665-677
Author(s):  
Kiflom Gebremedhn Kelele ◽  
Aschalew Tadesse ◽  
Tegene Desalegn ◽  
Suresh Ghotekar ◽  
Ruthramurthy Balachandran ◽  
...  
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Barium Titanate ◽  
Metal Ions ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Metal Ion ◽  
Dielectric Characteristics ◽  
Characterization Methods ◽  
Barium Strontium

Abstract The ferroelectric barium strontium titanate (Ba1-xSrxTiO3) is a homogeneous solid solution prepared from the mixture of barium titanate (BaTiO3), strontium titanate (SrTiO3) and titanium (IV) isopropoxide. Barium strontium titanate (BST) nanomaterials with improved permittivity and dielectric properties due to their nano-properties have attracted great interest for extensive and versatile applications as super capacitors, dielectrics, ceramics and catalysts. Introduction of metal ion dopants into the parent system of BST significantly alters its structural, morphological, electrical, optical and dielectric characteristics. This review is aimed at addressing synthesis, characterization methods, photocatalytic and electrical applications of metal ions doped BST nanomaterials. The effect of doping BST, through metal ions, on its properties and application with most probable reasons have been thoroughly discussed.

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