Aromatic polyimides: Synthesis, characterization, and evaluation of electric strength

Bjellheim, P.; Helgee, Bertil

doi:10.1002/app.1993.070480911

Cited by 8 publications

(4 citation statements)

References 21 publications

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“…Meanwhile, the ZnO particles acted as heterogeneous nucleation. LDPE molecules made the crystallization around the additive particles which could improve the crystallinity of ZnO/LDPE composites [21,22]. In the wake of doping ZnO particles size increased, the hererogeneous nucleation faded.…”

Section: Methodsmentioning

confidence: 99%

Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites

Cheng

Bai²,

Guang

et al. 2018

Materials

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The melt blending was used to prepare 3 wt% ZnO/low density polyethylene (ZnO/LDPE) nanocomposites in this article. The effect of different inorganic ZnO particles doping on the dielectrical property and crystal habit of LDPE matrix was explored. The nanoparticles size was 9 nm, 30 nm, 100 nm, and 200 nm respectively. Scanning electron microscope (SEM) was used to characterize ZnO nanoparticles whereas differential scanning calorimetry (DSC) was used to make thermal characterization of the samples. Besides, the AC (alternating current), DC (direct current breakdown characteristics and electrical conductivity of the nanocomposites was studied in this article. The experimental results showed that nano-ZnO/LDPE composites had the advantages such as small crystal size, high crystallization rate and crystallinity owing to nano-ZnO particles doping, when doping nano-ZnO particles size was 30 nm, the ZnO/LDPE nanocomposite crystallinity crest value 39.77% appeared. At the mean time, the DC and AC breakdown field strength values of composites were 138.0 kV/mm and 340.4 kV/mm respectively. They were the maximal values which improved 8.24% and 13.85% than LDPE. The AC breakdown field strength of samples decreased with specimen thickness increase. The DC breakdown field strength of LDPE and ZnO/LDPE composites were greater than AC breakdown field strength. From the conductivity experimental result it could be seen that when the experimental temperature and electric field intensity rose, the current density and conductivity of ZnO/LDPE composites increased with the enlargement of ZnO particles size. But the values were less than which of LDPE.

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Section: Methodsmentioning

confidence: 99%

Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites

Cheng

Bai²,

Guang

et al. 2018

Materials

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“…Besides, the nanoparticles were dispersed in the matrix homogeneously. The higher barrier would have to be overcome in the electronic formation of conductive paths [29,30]. Being comtransition.…”

Section: Breakdown Characteristic Test and Analysismentioning

confidence: 99%

The Dielectric Properties Improvement of Cable Insulation Layer by Different Morphology Nanoparticles Doping into LDPE

2019

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Low density polyethylene (LDPE) doped with inorganic nano-MMT and nano-ZnO particles improved the dielectric properties of the cable insulation layer. In this article, nano-MMT/LDPE and nano-ZnO/LDPE composites were prepared by polymer intercalation and melt blending, respectively. The octadecyl quaternary ammonium salt and silane coupling agent were applied for surface modification in nano-MMT and nano-ZnO particles, and this then improved the compatibility of nanoparticles and polymeric matrix. These samples were characterized by FTIR, PLM, DSC and TSC, from which the effect of nanoparticles doping on polymer crystal habit and interface traps would be explored. In these experiments, the AC breakdown characteristics and space charge characteristic of different composites were studied. The experimental results showed that the interface bonding of nanoparticles and polymer was improved by coupling agents modifying. The dispersion of nanoparticles in matrix was better. When the mass fraction of nanoparticles doping was 3 wt.%, the crystallization rate and crystallinity of composites increased, and the crystalline structure was more complete. Besides, the amorphous regions in material decreased and the conducting channel was circuitous. At this time, the breakdown field strength of nano-MMT/LDPE and nano-ZnO/LDPE increased by 10.3% and 11.1%, compared to that of pure LDPE, respectively. Furthermore, the density and depth of interface traps in polymer increased with nanoparticles doping. Nano-MMT and nano-ZnO could both restrain the space charge accumulation, and the inhibiting effect of nano-ZnO was more visible.

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“…This is supported by Mason [ 8 ] who reported that polypropylene (PP) breakdown is usually assisted by surface discharges coming from the transformer oil surrounding the sample under test. Likewise, Helgee and Bjellheim [ 9 ] and Bjellheim and Helgee [ 10 ] reached the same conclusion for polyimide (PI) films by showing that partial discharges (PDs) in the surrounding oil preceded breakdown for the thickest samples and that the oil permittivity had a significant influence.…”

Section: Introductionmentioning

confidence: 71%

“…[11] For instance, it can be found as a coating film or tape for power device passivation, [12] wafer-level packaging [13] isolation barrier for digital isolators, [14] or in transmission cables. [15] Over the last decades, the dielectric breakdown strength of PI films, mostly reported on Kapton tapes or on spincoated films, have been widely investigated under AC, [9,10,[16][17][18][19][20][21][22] DC [16,17,[23][24][25][26] or impulse [18] voltages. From this extensive literature, the thickness-dependent dielectric breakdown has been extracted and presented in Figure 1.…”

Section: State-of-the-art Of Polyimide Breakdown Field Versus Thickne...mentioning

confidence: 99%

Intrinsic AC Dielectric Breakdown Strength of Polyimide Films at the Extreme: New Breakthrough Insights on Thickness Dependence

Diaham,

Lambkin,

O'Sullivan

et al. 2023

Adv Materials Inter

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To date, the AC dielectric breakdown strength of polyimide (PI) films, as for most polymers, is understood to follow a thickness dependency with a measured power law exponent, n ≈ 0.5. However, this work experimentally demonstrates that the AC dielectric strength of PI films is quasi‐thickness independent. Evidence is presented showing that the thickness dependency described in the literature can be explained by an extrinsic failure mode, driven by partial discharges occurring at the dielectric‐oil‐electrode triple point. Triple points can be avoided by electrode encapsulation, which subsequently recovers a purely intrinsic failure mode for PI films over a large thickness range. Consequently, the AC dielectric strength of thick PI films is intrinsic and quasi‐thickness independent, at least for film thickness up to 60 µm. For the first time, a “theoretical” AC breakdown field for PI films is reported as ≈520 Vrms µm−1. Finally, the highest experimental breakdown field values are obtained here with 505 Vrms µm−1 and 705 Vµm−1 under AC and DC fields, respectively.

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Aromatic polyimides: Synthesis, characterization, and evaluation of electric strength

Cited by 8 publications

References 21 publications

Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites

Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites

The Dielectric Properties Improvement of Cable Insulation Layer by Different Morphology Nanoparticles Doping into LDPE

Intrinsic AC Dielectric Breakdown Strength of Polyimide Films at the Extreme: New Breakthrough Insights on Thickness Dependence

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