Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Silicone rubber, particularly poly(dimethylsiloxane) (PDMS), has been increasingly used
in the manufacture of outdoor high voltage insulators in the recent years. PDMS offers
several advantages that make it suitable for outdoor use, such as low weight, a
hydrophobic surface, stability, and excellent performance in heavily polluted
environments. PDMS surfaces can, however, become progressively hydrophilic due to
surface oxidation caused by corona discharge, UV radiation and acid rain.
In this study, PDMS samples of controlled formulations as well as six commercial
insulator materials four PDMS based and two ethylene propylene diene monomer
(EPDM) based were exposed to various accelerated weathering conditions for various
periods of time in order to track changes in the material over time. The ageing regimes
developed and used to simulate the potential surface degradation that may occur during
in-service usage included needle corona and French corona ageing, thermal ageing, UV-B
irradiation (up to 8000 hours) and acid rain (up to 200 days).
Both the chemical and physical changes in the materials were monitored using a wide
range of analytical techniques, including: static contact angle measurements (SCA),
optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive
spectroscopy (EDS), gas chromatography (GC), gas chromatography/mass spectroscopy
(GC/MS), size-exclusion chromatography (SEC), Fourier-transform infrared photoacoustic
spectroscopy (FTIR-PAS) and slow positron beam techniques (PAS).
A low molecular weight (LMW) uncrosslinked PDMS model compound was used to
further study the chemical effects of corona exposure on PDMS materials.
PDMS showed far better performance than EPDM, in terms of resistance to the various
ageing regimes and “hydrophobicity recovery”. / AFRIKAANSE OPSOMMING: Silikoonrubber, spesifiek polidimetielsiloksaan (PDMS), is gedurende die afgelope paar
jaar toenemend gebruik in die vervaardiging van buitelughoogspanningisolators. PDMS
het baie voordele vir gebruik in elektriese isolators soos ‘n laer massa, ʼn hidrofobiese
oppervlak, stabiliteit en uitstekende werking in hoogsbesoedelde omgewings. Die
hidrofobiese oppervlakte kan egter gelydelik hidrofilies word weens oppervlakoksidasie
as gevolg van korona-ontlading, UV-bestraling en suurreën.
In hierdie studie is PDMS monsters van verskillende samestellings sowel as ses
kommersiële isolators (vier PDMS en twee etileenpropileenrubber (EPDM)) blootgestel
aan verskillende versnelde weersomstandighede vir verskillende periodes om die
veranderinge in die materiale te monitor. Die verskillende materiale is gerangskik
volgens hulle werking oor ‘n periode van tyd. Dit het ook ‘n geleentheid gebied om die
eienskappe van die verskillende samestellings te bestudeer. Die tegnieke wat ontwikkel is
om die moontlike oppervlakdegradasie te simuleer, het naald-korona, “French” korona,
UVB-bestraling (tot 8000 uur) en suurreën (tot 200 dae) ingesluit.
Beide die chemiese en die fisiese veranderinge in die materiale is gemonitor met behulp
van verskeie tegnieke soos statiese kontakhoekbepaling, optiese mikroskopie,
skandeerelektronmikroskopie, energieverspreidingsspektroskopie, gaschromatografie,
grootte-uitsluitingschromatografie, foto-akoestiese Fouriertransforminfrarooi (PASFTIR)
en stadige-positronspektroskopie (PAS). ʼn Lae molekulêre massa PDMS
modelverbinding is gebruik om die chemiese effek van korona te bestudeer.
Die PDMS materiale het baie beter vertoon teenoor die EPDM materiale in terme van
hulle herstel van hidrofobisiteit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17749 |
| Date | 12 1900 |
| Creators | Elbuzedi, Mohamed |
| Contributors | Mallon, P.E., Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiv, 160 leaves : ill. |
| Rights | Stellenbosch University |
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