Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:
The work presented in this dissertation describes the use of coaxial electrospinning of
two miscible polymer solutions in the preparation of core-shell fibres with a semicrystalline
core of poly(L-lactic acid) and an amorphous shell of poly(D,L-lactic
acid). Additionally it describes using these fibres in the production of single polymer
composite yarns and films. These materials can potentially be used in applications that
require biodegradable and fibre-reinforced composite materials e.g. suture yarns.
Traditional methods, such as TEM, when used to analyse the core-shell fibre structure
were not successful with the polymer system used. A method was developed to
validate core-shell fibre structure by selective dissolution of the shell material and
correlating analyses of the separated components using differential scanning
calorimetry (DSC) and optical rotation. The effects of solution concentration and flow
rate on resultant core-shell fibre diameters were investigated. Core-solution flow rate
was shown to be the most significant variable affecting the core and core-shell fibre
diameters.
A thermal processing window exists between the glass transition temperature of the
amorphous PDLLA shell material and the crystalline melting temperature of the semicrystalline
PLLA core material. Heating these core-shell fibres within this processing
window resulted in flow and fusion of overlapping shells of these core-shell fibres at
their surfaces while the fibrous core components remained intact and reinforced the
resulting composite material. This approach was used to produce single polymer
composite yarns and films. Thermal treatments on yarns were shown to increase
crystallinity of the cores and therefore the modulus and yield strength of the fibres
when compared to untreated yarns. / AFRIKAANSE OPSOMMING:
Die werk wat in hierdie tesis voorgelê word, beskryf die gebruik van koaksiale
elektro-spinnery van twee wedersydsoplosbare polimeeroplossings in die
vervaardiging van kern-skilvesels met ‘n gedeeltelik-kristallyne kern van poli-Lmelksuur
(PLLA) en ‘n amorfe skil van poli-D,L-melksuur (PDLLA). Verder beskryf
dit die gebruik van hierdie vesels in die vervaardiging van enkel-polimeer
saamgestelde-materiaalgarings en -films. Hierdie materiale kan moontlik gebruik
word in toepassings wat bio-afbreekbare en veselversterkte saamgestelde materiale
vereis, soos byvoorbeeld chirurgiese steke.
Die polimeervesels wat in hierdie studie gebruik is, kon nie gekaraktiseer word met
behulp van transmissie-elektronmikroskopie (TEM), wat gewoonklik gebruik word in
die bestudering van kern-skilvesels, nie. ‘n Alternatiewe karakteriseringsmetode is
ontwikkel om te bevestig dat die gevormde vesels wel ‘n kern-skilstruktuur het.
Hierdie metode het behels dat die skil van die kern-skilvesel selektief opgelos is,
waarna beide komponente (d.i. kern en skilmateriale) bestudeer is met behulp van
differensiële skanderingskalorimetrie en optiese rotasie. Die invloed van
polimeeroplossingskonsentrasie en –vloeitempo op die gevormde kern-skilvesels is
daarna ondersoek en die vloeitempo van die kernoplossing is geïdentifiseer as die
prosesinsetwaarde wat die mees beduidende invloed het op die deursnee van die
vesels.
Daar bestaan ‘n temperatuurinterval tussen die glasoorgangstemperatuur van
die amorfe PDLLA skilmateriaal en die kristallyne smeltpunt van die gedeeltelikkristallyne
PLLA kernmateriaal. Verwerking van die kern-skilvesels by ‘n
temperatuur binne hierdie interval het gelei tot vervloeiing en samesmelting van die
oorvleuelende skille van die kern-skilvesels, terwyl die veselagtige kernkomponente
van die vesels heel gebly het en opgetree het as versterking binne-in die saamgestelde
materiaal wat gevorm het. Hierdie benadering is gebruik om enkelpolimeersaamgestelde-
materiaalgarings en –films te vervaardig. ‘n Vergelykende
studie tussen onbehandelde en hitte-behandelde enkel-polimeer-saamgesteldemateriaalgarings
het aangetoon dat die hittebehandeling gelei het tot ‘n verhoging in
die kristalliniteit van die veselkerne en daarom ook ‘n verhoging in die modulus en
breeksterkte van die garings tot gevolg gehad het.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4289 |
| Date | 03 1900 |
| Creators | Kriel, Haydn |
| Contributors | Sanderson, Ron D., Gericke, Adine, University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
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