A Review of Polyolefin-Insulation Materials in High Voltage Transmission; From Electronic Structures to Final Products.

This review focuses on the use of polyolefins in high-voltage direct-current (HVDC) cables and capacitors. A short description of the latest evolution and current use of HVDC cables and capacitors is first provided, followed by the basics of electric insulation and capacitor functions. Methods to determine dielectric properties are described, including charge transport, space charges, resistivity, dielectric loss, and breakdown strength.

Tuneable conductivity at extreme electric fields in ZnO tetrapod-silicone composites for high-voltage power cable insulation.

Resistive Field Grading Materials (RFGM) are used in critical regions in the electrical insulation system of high-voltage direct-current cable systems. Here, we describe a novel type of RFGM, based on a percolated network of zinc oxide (ZnO) tetrapods in a rubber matrix. The electrical conductivity of the composite increases by a factor of 10 for electric fields > 1 kV mm, as a result of the highly anisotropic shape of the tetrapods and their significant bandgap (3.

Lamellae-controlled electrical properties of polyethylene - morphology, oxidation and effects of antioxidant on the DC conductivity.

Destruction of the spherulite structure in low-density polyethylene (LDPE) is shown to result in a more insulating material at low temperatures, while the reverse effect is observed at high temperatures. On average, the change in morphology reduced the conductivity by a factor of 4, but this morphology-related decrease in conductivity was relatively small compared with the conductivity drop of more than 2 decades that was observed after slight oxidation of the LDPE (at 25 °C and 30 kV mm). The conductivity of LDPE was measured at different temperatures (25-60 °C) and at different electrical field strengths (3.

Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene--Butyl Acrylate) Composites for Electrical Applications.

Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (-butyl methacrylate) (PBMA) in a poly(ethylene--butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction.

Reduced and Surface-Modified Graphene Oxide with Nonlinear Resistivity.

Field-grading materials (FGMs) are used to reduce the probability for electrical breakdowns in critical regions of electrical components and are therefore of great importance. Usually, FGMs are heavily filled (40 vol.%) with semi-conducting or conducting particles.

Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces.

Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites.

Surface ionization state and nanoscale chemical composition of UV-irradiated poly(dimethylsiloxane) probed by chemical force microscopy, force titration, and electrokinetic measurements.

The surface chemistry and ionization state of cross-linked poly(dimethylsiloxane) (PDMS) exposed to UV/ozone were studied as a function of treatment time. Various complementary and independent experimental techniques were utilized, which yielded information on the macroscopic as well as the nanometric scale. The average chemical composition of the PDMS surface was quantitatively investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS).

Nanoscale hydrophobic recovery: A chemical force microscopy study of UV/ozone-treated cross-linked poly(dimethylsiloxane).

Chemical force microscopy (CFM) in water was used to map the surface hydrophobicity of UV/ozone-treated poly(dimethylsiloxane) (PDMS; Sylgard 184) as a function of the storage/recovery time. In addition to CFM pull-off force mapping, we applied indentation mapping to probe the changes in the normalized modulus. These experiments were complemented by results on surface properties assessed on the micrometer scale by X-ray photoelectron spectroscopy and water contact-angle measurements.