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Title: Electroluminescence and ageing of polyethylene
Author: Mills, David H.
ISNI:       0000 0004 2727 7210
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2012
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Electrical insulation is known to age when under electrical stress. One cause of this is thought to relate to the movement and build up of charge within the insulation. The emission of a low level of light from polymeric materials when under electrical stressing is shown to occur before the onset of currently detectable material degradation. This light is termed electroluminescence (EL)and under an ac electric field is thought to relate to the interaction of charge in close proximity to the electrode-polymer interface. Understanding the cause of this light emission gives a very high resolution way of monitoring charge interaction and its influence on material ageing. This report presents the improvement to a system to measure changes in EL emission during the cycle of the applied field (point on wave measurements) under various electric fields. To investigate the relationship between EL and ageing, 100 �m, low-density polyethylene (LDPE) films were ultraviolet (UV) aged in 3 and 7 day intervals up to 17 days. The samples were aged in both air and nitrogen environments to separate the affect of photo-oxidation from photo irradiation reactions on charge movement. Changes as a result of ageing were characterised in terms of optical, chemical and electrical properties. These were investigated using ultraviolet and visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy, ac ramp breakdown measurements and dielectric spectroscopy. The accumulation of space charge (SC) was then investigated using the pulsed electro acoustic (PEA) technique. This collection of results were used to explain changes in EL in terms of intensity and phase difference. A model using the bipolar charge recombination theory was then developed using trends shown in the characterising measurements to explain changes in EL. Results support the use of EL as a tool to investigate changes in charge movement very near the electrode-polymer interface.
Supervisor: Lewin, Paul Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering ; QC Physics