Electric field inducement of montmorillonite in ldpe and properties of electrical tree growing in this composite

Abstract

The electric field-induced method is proposed to orient montmorillonite (MMT) in lowdensity polyethylene (LDPE) and improve the electrical tree resistance of LDPE. A new orientation setup for electrical inducement was designed to achieve MMT orientation in the LDPE/MMT composite. The effect of electrically induced orientation was characterized by X-ray diffraction, ultraviolet-visible spectroscopy, and scanning electron microscopy. The initiation and propagation properties of electrical trees in the LDPE/MMT composite before and after the electrically induced treatment were investigated and compared. Results indicate that the electric field contributes to the uniform dispersion of MMT in LDPE and causes MMT layers to shift in a direction parallel to the electric field. The LDPE/MMT composite after the electrically induced treatment showed higher capability for suppressing electrical trees under the powerfrequency field.

Polyethylene Nanocomposites for Power Cable Insulations

“…Addition of a certain content of montmorillonite MMT to PE improved the electrical treeing resistance of the material. This filler effect depended, among others, on the preparation approach and dispersion degree of MMT in the polymer (Figure 31a) [184]. It was also observed that the shapes of the trees were changed upon the addition of MMT.…”

“…Electrical treeing is one of the main causes for failure and damage in electrical power cable insulations [184]. Electrical trees are networks of very thin channels (including gases at high pressures) initiated near insulation and/or electrodes defects, which develop in the insulation during the electrical equipment operation [133,185].…”

“…In addition, the results revealed that the tree lengths were shorter by about 60% in LDPE/MMT nanocomposites compared to unfilled LDPE. The influence of the MMT dispersion morphology (isotropy in random arrangement or anisotropy in oriented arrangement) on the development of electric trees in LDPE was studied by Yang et al [184]. The authors orientated the nanofillers in the matrix by applying an electric field that induced the field-controlled orientation, aggregation and arrangement of the nanoparticles.…”

“…When the electric field was set for the tree initiation, the MMT particles were arranged perpendicular with respect to the direction of the electric field, acting as a barrier that inhibited electrical tree initiation (Figure 31a). The MMT barrier interrupted the growth and the original direction of tree growth [184].…”

“…( a ) Variation in time t of electric tree’s average lengths L developed in unfilled LDPE (LDPE), LDPE with 5 wt % of MMT (LDPE/MMT) and LDPE with 5 wt % of MMT treated in an alternating electric field (LDPE/MMT (AC)). Reprinted, with permission by IEEE, from reference [184]. ( b ) Length dispersion of electrical trees in PE and PE/MMT composites with varying content of MMT: 0 (PE), 0.5 (PE/MMT-0.5), 1 (PE/MMT-1), 3 (PE/MMT-3) and 5 wt % (PE/MMT-5).…”