On the effects of molecular composition, morphology and ageing on the electrical properties of polyethylene

Abstract

Polyethylene is widely used as the basis for the insulation in high voltage cables, commonly, in the form of cross linked low density polyethylene (XLPE). With time, the chemical and electrical properties of the pristine polymer begin to change, depending on the molecular architecture, morphology and ageing processes. In this work, thermal treatment, based on accelerated ageing in air was performed on the exposed surface of polyethylene blend films (HDPE/LDPE) at temperatures above the melting point for various treatment times. The ageing degrees were quantified by Fourier transform infrared (FTIR) spectroscopy, while dielectric spectroscopy was used to investigate the dielectric response. Space charge dynamics were measured using the pulsed electroacoustic (PEA) technique. It was found that the dielectric loss after long treatment times was significantly increased, corresponding with the carbonyl index. Furthermore, space charge results show that homocharge was increased at short treatment time; however, it is noticeable that, after long treatment times, charge injection appeared to be affected by surface oxidation and, in this way ageing has a marked effect on the electrical behaviour of the blend.

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Identifiers

ORCID for Somyot Tantipattarakul: orcid.org/0000-0001-5814-1277

ORCID for Alun Vaughan: orcid.org/0000-0002-0535-513X

ORCID for Thomas Andritsch: orcid.org/0000-0002-3462-022X

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