scholarly journals Dynamic Thermomechanical Analysis on Water Tree Resistance of Crosslinked Polyethylene

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 746 ◽  
Author(s):  
Kun Sun ◽  
Junqi Chen ◽  
Hong Zhao ◽  
Weifeng Sun ◽  
Yinsheng Chen ◽  
...  
Keyword(s):  
Amorphous Phase ◽  
Uv Irradiation ◽  
Tree Growth ◽  
Thermomechanical Analysis ◽  
Polymer Chains ◽  
Crosslinking Reaction ◽  
Crosslinking Degree ◽  
Water Tree ◽  
Tree Resistance ◽  
Β Relaxation

The water tree resistance of crosslinked polyethylene (XLPE) initiated by ultraviolet (UV) irradiation technique is investigated through a water blade electrode method, and the effects of the mechanism of UV irradiation crosslinking on inhibiting water tree growth are revealed with dynamic thermomechanical analysis (DMA). The accelerated water tree aging experiment shows that UV irradiation crosslinking inhibits the growth rate of water trees, and the water tree length and width is reduced with the increase of the crosslinking degree of XLPE. The DMA result demonstrates that the molecular activity of the amorphous phase in XLPE as represented by polyethylene β-relaxation is gradually intensified with the increase of the crosslinking reaction. Combined with the fatigue mechanism of water tree growth in semi-crystalline polymers, it is suggested that the UV irradiation crosslinking reaction can significantly improve the anti-water-tree performance of linear low-density polyethylene (LLDPE). The crosslinking bond in the amorphous phase of UV-photoinitiated crosslinking polyethylene can produce a large number of cross-connected polymer chains, by which the length of fiber is obviously increased, leading to an reduced force from the micro-water beads onto the crack tip and thus decreasing the rate of the material being destroyed by micro-water beads.

scholarly journals Water-Tree Resistant Characteristics of Crosslinker-Modified-SiO2/XLPE Nanocomposites

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1398
Author(s):  
Yong-Qi Zhang ◽  
Xuan Wang ◽  
Ping-Lan Yu ◽  
Wei-Feng Sun
Keyword(s):  
Electric Fields ◽  
Tree Growth ◽  
Mechanical Analysis ◽  
Water Molecules ◽  
Crosslinking Degree ◽  
Water Tree ◽  
Tree Resistance ◽  
Alternating Electric Fields ◽  
Trimethylolpropane Triacrylate ◽  
Mechanical Performances

Trimethylolpropane triacrylate (TMPTA) as a photoactive crosslinker is grafted onto hydrophobic nanosilica surface through click chemical reactions of mercapto double bonds to prepare the functionalized nanoparticles (TMPTA-s-SiO2), which are used to develop TMPTA-s-SiO2/XLPE nanocomposites with improvements in mechanical strength and electrical resistance. The expedited aging experiments of water-tree growth are performed with a water-knife electrode and analyzed in consistence with the mechanical performances evaluated by means of dynamic thermo-mechanical analysis (DMA) and tensile stress–strain characteristics. Due to the dense cross-linking network of polyethylene molecular chains formed on the TMPTA-modified surfaces of SiO2 nanofillers, TMPTA-s-SiO2 nanofillers are chemically introduced into XLPE matrix to acquire higher crosslinking degree and connection strength in the amorphous regions between polyethylene lamellae, accounting for the higher water-tree resistance and ameliorated mechanical performances, compared with pure XLPE and neat-SiO2/XLPE nanocomposite. Hydrophilic TMPTA molecules grafted on the nano-SiO2 surface can inhibit the condensation of water molecules into water micro-beads at insulation defects, thus attenuating the damage of water micro-beads to polyethylene configurations under alternating electric fields and thus restricting water-tree growth in amorphous regions. The intensified interfaces between TMPTA-s-SiO2 nanofillers and XLPE matrix limit the segment motions of polyethylene molecular chains and resist the diffusion of water molecules in XLPE amorphous regions, which further contributes to the excellent water-tree resistance of TMPTA-s-SiO2/XLPE nanocomposites.

scholarly journals Water-Tree Resistability of UV-XLPE from Hydrophilicity of Auxiliary Crosslinkers

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4147
Author(s):  
Jun-Qi Chen ◽  
Xuan Wang ◽  
Wei-Feng Sun ◽  
Hong Zhao
Keyword(s):  
Molecular Simulation ◽  
Amorphous Phase ◽  
Viscoelastic Properties ◽  
Binary Systems ◽  
Interaction Parameters ◽  
Water Molecules ◽  
Stress Strain ◽  
Mixing Energy ◽  
Water Tree ◽  
Tree Resistance

The water-resistant characteristics of ultraviolet crosslinked polyethylene (UV-XLPE) are investigated specially for the dependence on the hydrophilicities of auxiliary crosslinkers, which is significant to develop high-voltage insulating cable materials. As auxiliary crosslinking agents of polyethylene, triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), and N,N′-m-phenylenedimaleimide (HAV2) are individually adopted to prepared XLPE materials with the UV-initiation crosslinking technique, for the study of water-tree resistance through the accelerating aging experiments with water blade electrode. The stress–strain characteristics and dynamic viscoelastic properties of UV-XLPE are tested by the electronic tension machine and dynamic thermomechanical analyzer. Monte Carlo molecular simulation is used to calculate the interaction parameters and mixing energy of crosslinker/water binary systems to analyze the compatibility between water and crosslinker molecules. Water-tree experiments verify that XLPE-TAIC represents the highest ability to inhibit the growth of water-trees, while XLPE-HAV2 shows the lowest resistance to water-trees. The stress–strain and viscoelastic properties show that the concentration of molecular chains connecting the adjacent lamellae in amorphous phase of XLPE-HAV2 is significantly higher than that of XLPE-TAIC and XLPE-TMPTMA. The molecular simulation results demonstrate that TAIC/water and TMPTMA/water binary systems possess a higher hydrophilicity than that of HAV2/water, as manifested by their lower interaction parameters and mixing free energies. The auxiliary crosslinkers can not only increase the molecular density of amorphous polyethylene between lamellae to inhibit water-tree growth, but also prevent water molecules at insulation defects from agglomerating into micro-water beads by increasing the hydrophilicity of auxiliary crosslinkers, which will evidently reduce the damage of micro-water beads on the amorphous phase in UV-XLPE. The better compatibility of TAIC and water molecules is the dominant reason accounting for the excellent water resistance of XLPE-TAIC.

scholarly journals Polyethylene Nanocomposites for Power Cable Insulations

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 24 ◽  
Author(s):  
Ilona Pleşa ◽  
Petru Noţingher ◽  
Cristina Stancu ◽  
Frank Wiesbrock ◽  
Sandra Schlögl
Keyword(s):  
Electrical Performance ◽  
Power Cable ◽  
Power Cables ◽  
Structure Property ◽  
Thermoplastic Polymers ◽  
Water Tree ◽  
Tree Resistance ◽  
Structure Property Relationships ◽  
Aging Mechanisms ◽  
Comprehensive Study

This review represents a comprehensive study of nanocomposites for power cables insulations based on thermoplastic polymers such as polyethylene congeners like LDPE, HDPE and XLPE, which is complemented by original results. Particular focus lies on the structure-property relationships of nanocomposites and the materials’ design with the corresponding electrical properties. The critical factors, which contribute to the degradation or improvement of the electrical performance of such cable insulations, are discussed in detail; in particular, properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, space charge, electrical and water tree resistance behavior and electric breakdown of such nanocomposites based on thermoplastic polymers are described and referred to the composites’ structures. This review is motivated by the fact that the development of polymer nanocomposites for power cables insulation is based on understanding more closely the aging mechanisms and the behavior of nanocomposites under operating stresses.

The Effect of Service and Test Conditions on Water Tree Growth in XLPE Cables

1983 ◽  
Vol PER-3 (7) ◽  
pp. 33-33
Author(s):  
Jarle Sletbak ◽  
Erling Ildstad
Keyword(s):  
Tree Growth ◽  
Water Tree ◽  
Test Conditions

scholarly journals Evaluation of graphene/crosslinked polyethylene for potential high voltage direct current cable insulation applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuan Li ◽  
Guangya Zhu ◽  
Kai Zhou ◽  
Pengfei Meng ◽  
Guodong Wang
Keyword(s):  
Space Charge ◽  
High Voltage ◽  
Direct Current ◽  
Tensile Yield Strength ◽  
Scanning Calorimetry ◽  
Crosslinking Degree ◽  
High Voltage Direct Current ◽  
Water Tree ◽  
Mechanical And Electrical Properties ◽  
Aging Test

AbstractThis paper evaluates the potential usage of graphene/crosslinked polyethylene (graphene/XLPE) as the insulating material for high voltage direct current (HVDC) cables. Thermal, mechanical and electrical properties of blends with/without graphene were evaluated by differential scanning calorimetry (DSC), tensile strength, DC conductivity, space charge measurements and water tree aging test. The results indicate that 0.007–0.008% weight amount of graphene can improve the mechanical and electrical insulation properties of XLPE blends, namely higher tensile/yield strength, improved space charge distribution, and shorter/fewer water tree branches. The improvements mainly attribute to the high stiffness of graphene, deep traps introduced by the interaction zones of graphene and XLPE, and the blockage effect of graphene within XLPE. For thermal performance of XLPE blends, graphene nano-fillers have but limited improvement. The crystallinity of the blends barely changes with the addition of graphene. However, the crosslinking degree increases as the additive-like amounts of graphene doped. The above findings provide a guide for tailoring lightweight XLPE materials with excellent mechanical and electrical performances by doping them with a small amount of graphene.

scholarly journals Uncovering β-relaxations in amorphous phase-change materials

2020 ◽  
Vol 6 (2) ◽  
pp. eaay6726 ◽  
Author(s):  
Si-Xu Peng ◽  
Yudong Cheng ◽  
Julian Pries ◽  
Shuai Wei ◽  
Hai-Bin Yu ◽  
...  
Keyword(s):  
Phase Change ◽  
Amorphous Phase ◽  
Amorphous Materials ◽  
Phase Change Materials ◽  
Special Kind ◽  
Relaxation Processes ◽  
Glass Transitions ◽  
Mechanical Spectroscopy ◽  
Characteristic Features ◽  
Β Relaxation

Relaxation processes are decisive for many physical properties of amorphous materials. For amorphous phase-change materials (PCMs) used in nonvolatile memories, relaxation processes are, however, difficult to characterize because of the lack of bulk samples. Here, instead of bulk samples, we use powder mechanical spectroscopy for powder samples to detect the prominent excess wings—a characteristic feature of β-relaxations—in a series of amorphous PCMs at temperatures below glass transitions. By contrast, β-relaxations are vanishingly small in amorphous chalcogenides of similar composition, which lack the characteristic features of PCMs. This conclusion is corroborated upon crossing the border from PCMs to non-PCMs, where β-relaxations drop substantially. Such a distinction implies that amorphous PCMs belong to a special kind of covalent glasses whose locally fast atomic motions are preserved even below the glass transitions. These findings suggest a correlation between β-relaxation and crystallization kinetics of PCMs, which have technological implications for phase-change memory functionalities.

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