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Effect of Heat Treatment on Morphology and Dielectric Properties of Polyethylene
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Polyethylene is used extensively as an insulating material in high voltage power cables, it is

therefore important to understand the behaviour of polyethylene under different conditions.

This is a study regarding the relation of heat treatment and the effect of morphological

changes on the dielectric properties of polyethylene samples. Polyethylene granulates were

pressed to 1 mm thick circular plaque samples that were heat treated differently. The heat

treatments were conducted in a vacuum oven. Heat treated samples were tested for

morphological changes with Differential Scanning Calorimetry (DSC) and dielectric property

changes were studied with an IDAX 300 Dielectric Spectroscopy Analyser and a TREK 30/30

high voltage amplifier, allowing measurements in the frequency range 0.1 mHz

– 100 Hz for

voltages up to 30 kV. The experimental results were analysed to understand the co-relation

among these parameters. A literature review has been conducted on polyethylene morphology

to understand their behaviour under different annealing conditions. A phenomenon that has

been noticed during the experiments is that the samples swell with annealing; the thickness

change effects the dielectric measurements as well. For this reason an extensive study has

been conducted on the effect different temperature and time of heat treatment had on the

samples.

Heat treatment has effects on the properties of polyethylene samples, but the effect of heat

treatment was not only on the morphology but also on the physical dimension of the samples.

The samples change their thickness with heat treatment along with their morphology. The

effect of morphological changes on the dielectric property of polyethylene samples has not

been found to be eminent.

This study was focused on relatively thicker samples (1 mm) compared to the existent

scientific literature (0.1-0.2 mm). There are very limited research literatures available on the

relation of morphology and electrical properties of polyethylene; this work is an attempt to

contribute to the knowledge. Also the effect of samples swelling with annealing and its effect

on electric measurements is not found in existing literatures. This work will also contribute

understanding the effect of sample swelling on measurements.

Abstract [sv]

Polyeten används i stor utsträckning som ett isolermaterial i högspänningskablar, och därför

är det därför viktigt att förstå beteendet hos polyeten under olika förhållanden. Detta är en

studie angående relationen mellan värmebehandling och effekten av morfologiska

förändringar av de dielektriska egenskaperna hos polyeten. Polyeten granulat pressades till 1

mm tjocka cirkulära skivor som sedan värmebehandlades olika. Värmebehandlingarna

utfördes i en vakuumugn. De värmebehandlade proverna testades för morfologiska

förändringar med differentiell svepkalorimetri (DSC) och de dielektriskaegenskaperna

studerades med en IDAX 300 Dielektrisk spektroskopi Analysator och en TREK 30/30

högspänningsförstärkare, vilken tillåter mätningar i frekvensområdet 0,1 mHz - 100 Hz för

spänningar upp till 30 kV. De experimentella resultaten analyserades för att förstå relationen

mellan dessa parametrar. En litteratur har utförts på polyeten morfologi för att förstå deras

beteende under olika anlöpningsförhållanden. Ett fenomen som har uppmärksammats under

experimenten är att proverna sväller med anlöpningenÄven tjockleken påverkar de

dielektriska mätningar. Av denna anledning utfördes en omfattande studie av effekten av olika

temperatur och tid för värmebehandling hade på proverna.

Värmebehandling har effekter på egenskaperna för polyetenprover, men effekten av

värmebehandlingen var inte bara på morfologin, utan också på den fysiska dimensionen av

proverna. Effekten av morfologiska förändringar på den dielektriska egenskapen hos

polyetenprover har inte befunnits vara framstående.

Denna studie var inriktad på relativt tjockare prover (1 mm) jämfört med den existerande

vetenskapliga litteraturen (0,1-0,2 mm). Det finns mycket lite litteratur kring relationen

mellan morfologi och elektriska egenskaper hos polyeten; detta arbete är ett försök att bidra

till kunskapen. Även effekten av provernas svällande efter anlöpning och dess effekt på

dielektriska mätningar finns befintliga litteraturen.

Place, publisher, year, edition, pages
2014. , 94 p.
Series
EES Examensarbete / Master Thesis, XR-EE-ETK 2014:017
Keyword [en]
Polyethylene, Morphology, Annealing, Sample Swelling, Dielectric Spectroscopy, Differential Scanning Calorimetry, Crystallinity, heat Treatment, Power Cable, High Voltage, Permittivity
Keyword [sv]
Polyeten, Morfologi, Anlöpning, Svällning, Dielektrisk spektroskopi, Differentiell svepkalorimetri, Kristallinitet, Värmebehandling, Kraftkabel, Högspänning, Permittivitet
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-156467OAI: oai:DiVA.org:kth-156467DiVA: diva2:766803
External cooperation
ABB AB
Examiners
Available from: 2014-12-01 Created: 2014-11-28 Last updated: 2014-12-01Bibliographically approved

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