Filler-content Dependence of Dielectric Properties of Low-Density Polyethylene/MgO Nanocomposites

Abstract

Recently, polymer nanocomposites (NCs) are gaining new attraction as insulating materials, since their superior dielectric properties are being recognized. In the present paper, basic dielectric properties of NCs of low-density polyethylene (LDPE) and magnesium oxide (MgO) nano-fillers with various filler contents are examined. The samples tested were LDPE/MgO NC sheets with a thickness of about 100 µm, which contain 1, 5, and 10 phr (parts per hundred parts of resin by weight) MgO particles with average and max diameters of 50 and 200 nm, respectively. As a reference, LDPE without MgO particles was also used. Instrumental analyses were carried out by ultraviolet-visible absorption spectroscopy (UVA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) spectroscopy, and Fourier-transform infrared absorption (FT-IR) spectroscopy. Permittivity was measured at temperatures from 20 to 100 °C for frequencies from 30 to 10 5 Hz. Conduction current was measured under dc electric field of 25 kV/mm. Space charge distribution was measured at room temperature by the pulsed electroacoustic method. Optical transparency first increases by the addition of MgO fillers up to 1 to 5 phr, and then it decreases. Thermal properties and morphology are insensitive to the filler addition, as far as those analyzable by XRD, FT-IR, and DSC are concerned.

Improved electrical insulating properties of LDPE based nanocomposite: Effect of surface modification of magnesia nanoparticles

“…With the increase of temperature, permittivity decreases monotonically in all the samples. This tendency is the sample's true temperature dependence, manifesting that the polarization is obstructed by thermal perturbation, which is consistent with Tanaka's result [35]. As shown in Fig.…”

Tree initiation and growth in LDPE/MgO nanocomposites and roles of nano fillers

“…10 (c). This process includes internal PD process so that a positive effect of nano fillers is considered to become evident in the filler content range of 2 phr, since it was already clarified that nano fillers act against PD erosion [5]. Tree lengths are ranged in mm order for treeing breakdown time measurement experiments.…”

“…Cross-linked polyethylene (XLPE) insulation with nano fillers is preferred for extra high voltage dc power cables, since it exhibited better dc dielectric performance than simple XLPE insulation [4]. In this regard, various dielectric properties of low density polyethylene (LDPE) with nano fillers such as MgO nano fillers have been intensively investigated as fundamental study [5] [6]. It is especially characteristic that LDPE/MgO nanocomposite exhibits much reduction in space charge formed inside insulation as compared to neat LDPE [7], resulting in avoiding dielectric failure due to the accumulation of space charge that usually appears in LDPE and XLPE insulation.…”

Highly sensitive location method of an abnormal temperature point in a cable by frequency domain reflectometry

“…3(b), a clear peak appears even when the temperature was increased by only 5 ºC from room temperature. Here, the change in ε r ' at temperatures around 20 to 30 ºC is as small as about 0.12% by the temperature change of 5 ºC for LDPE [9][10][11]. This in turn indicates that the change in Z 0 is less than 0.1%.…”

“…Therefore, ε r ' was measured for LDPE and PVC as a function of temperature and frequency. As a result, ε r ' increases in PVC with an increase in temperature, while it decreases in LDPE [8][9][10][11]. The characteristic impedance Z 0 of a cable depends on ε r ' in the form of Z 0 ∝ ε r ' -1/2 .…”