Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Impact Polypropylene Copolymers (IPCs) are extremely complex materials, consisting of a mixture of
polypropylene homopolymer and copolymers having different comonomer (ethylene) contents and
chemical composition distributions. IPC can only be effectively analysed by multidimensional
analytical approaches. For this, initially, the individual components have to be separated according to
any of their molecular characteristics, either by chemical composition distribution (CCD) or molar
mass distribution (MMD), followed by further analysis of these separated fractions with conventional
analytical techniques. The combination of preparative temperature rising elution fractionation (TREF)
with several other analytical techniques have been reported for the thorough characterization of this
material. However, even the combinations of these methods were of limited value due to the complex
nature of this polymer. Therefore, novel analytical approaches are needed for a more detailed
compositional analysis of IPCs.
This work describes a number of multidimensional analytical techniques that are based on the
combination of fractionation and hyphenated techniques. Firstly, preparative TREF was combined
with high temperature size exclusion chromatography-FTIR (HT SEC-FTIR), HT SEC-HPer DSC
(High Performance Differential Scanning Calorimetry) and high temperature two-dimensional liquid
chromatography (HT 2D-LC) for the comprehensive analysis of a typical impact polypropylene
copolymer and one of its midelution temperature TREF fractions. HT SEC-FTIR analysis provided
information regarding the chemical composition and crystallinity as a function of molar mass. Thermal
analysis of selected SEC fractions using a novel DSC method - High Speed or High Performance
Differential Scanning Calorimetry (HPer DSC) - that allows measuring of minute amounts of material
down to micrograms, yielded the melting and crystallization behaviour of these fractions which is
related to the chemical heterogeneity of this complex copolymer. High temperature 2D-LC analysis
provided the complete separation of this TREF fraction according to the chemical composition of each
component along with its molar mass distribution. In a second step, the compositional characterization by advanced thermal analysis (HPer DSC, Flash DSC 1, and solution DSC) of the
TREF-SEC fractions was extended to all semi-crystalline and higher temperature TREF fractions. By
applying HPer DSC at scan rates of 5−200°C/min and Flash DSC 1 at scan rates of 10−1000°C/s,
the metastability of one of the fractions was studied in detail. DSC measurements of TREF-SEC
cross-fractions at high scan rates in p-xylene successfully connected reversely to the slow scan rate
in TREF elution, if corrected for recrystallization. Finally, the exact chemical structure of all HT HPLC
separated components was determined by coupling of HT HPLC with FTIR spectroscopy via an LCTransform
interface. This novel approach revealed the capability of this hyphenated technique to
determine the exact chemical composition of the individual components in the complex TREF
fractions of IPCs. The HT HPLC–FTIR results confirmed the separation mechanism in HPLC using a
solvent gradient of 1-decanol/TCB and a graphitic stationary phase at 160°C. FTIR analysis provided
information on the ethylene and propylene contents of the fractions as well as on the ethylene and
propylene crystallinities. / AFRIKAANSE OPSOMMING: Impak Polipropileen Kopolimere (IPKe) is uiters komplekse materiale, bestaande uit 'n mengsel van
polipropileen homopolimeer en kopolimere met verskillende komonomeer (etileen) inhoud en
chemiese samestelling verspreiding. IPKe kan slegs doeltreffend ontleed word deur multidimensionele
analitiese benaderings te volg. Hiervoor moet die individuele komponente aanvanklik
eers geskei word volgens enige van hul molekulêre eienskappe, hetsy deur die chemiese
samestelling verspreiding (CSV) of molêre massa verspreiding (MMV), gevolg deur 'n verdere
ontleding van hierdie geskeide fraksies met konvensionele analitiese tegnieke. Die kombinasie van
voorbereidings temperatuur-verhogings eluasie fraksionering (TVEF) met verskeie ander analitiese
tegnieke is gerapporteer vir die deeglike karakterisering van hierdie materiaal. Maar selfs die
kombinasies van hierdie metodes was van beperkte waarde as gevolg van die komplekse aard van
hierdie polimeer. Daarom word nuwe analitiese benaderings benodig vir 'n meer gedetailleerde
komposisionele ontleding van IPKe.
Hierdie studie beskryf 'n aantal multidimensionele analitiese tegnieke wat gebaseer is op die
kombinasie van fraksionering en gekoppelde tegnieke. Eerstens is voorbereidings TVEF gekombineer
met hoë temperatuur grootte-uitsluitingschromatografie-FTIR (HT GUC-FTIR), HT GUC-HPer DSK en
hoë temperatuur twee-dimensionele vloeistof chromatografie (HT 2D-VC) vir die omvattende
ontleding van 'n tipiese impak polipropileen kopolimeer en een van sy mid-eluasie temperatuur TVEF
fraksies. HT GUC-FTIR analiese het inligting verskaf met betrekking tot die chemiese samestelling en
kristalliniteit as 'n funksie van molêre massa. Termiese analiese van geselekteerde GUC fraksies deur
gebruik te maak van 'n nuwe-DSK metode - Hoë Spoed of Hoë Prestasie Differensïele skandeer
kalorimetrie (HPer DSK) - wat die meting van klein hoeveelhede materiaal tot by mikrogram
hoeveelhede toelaat, het die smelt en kristallisasie gedrag van hierdie fraksies bepaal wat verwant is
aan die chemiese heterogeniteit van hierdie komplekse kopolimeer. Hoë temperatuur 2D-LC analiese
het die volledige skeiding van hierdie TVEF fraksie volgens die chemiese samestelling van elke
komponent saam met die molêre massa verspreiding moontlik gemaak. In 'n tweede stap, is die komposisionele karakterisering deur gevorderde termiese analiese (HPer DSK, Flash DSK 1 en
oplossing DSK) van die TVEF-GUC fraksies uitgebrei na alle semi-kristallyne en hoër temperatuur
TVEF fraksies. Deur die gebruik van HPer DSK, teen ’n skandeerspoed van 5-200°C / min, en Flash
DSK 1, teen ’n skandeerspoed van 10-1000°C / s, is die meta-stabiliteit van een van die fraksies in
detail bestudeer. DSK metings van TVEF-GUC kruis-fraksies by 'n hoë skandeeerspoed in p-xyleen
het suksesvol omgekeerd verbind aan die stadige skandeerspoed in TVEF eluasie, wanneer
gekorrigeer vir dekristallisatie. Ten slotte is die presiese chemiese struktuur van al die HT HPVC
geskeide komponente bepaal deur die koppeling van HT HPVC met FTIR spektroskopie deur middel
van 'n LC-transform-koppelvlak. Hierdie nuwe benadering het die vermoë van die gekoppelde tegniek
om die presiese chemiese samestelling van die individuele komponente in die komplekse TVEF
fraksies of IPKe te bepaal aan die lig gebring. Die HT HPVC-FTIR resultate het die
skeidingsmeganisme in HPVC bevestig deur die gebruik van ’n oplosmiddelgradiënt van 1-dekanol/TCB en 'n graphitiese stasionêre fase by 160°C. FTIR analiese verskaf inligting in verband
met die etileen en propileen inhoud van die fraksies sowel as die etileen en propileen krystalliniteit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80118 |
| Date | 03 1900 |
| Creators | Cheruthazhekatt, Sadiqali |
| Contributors | Pasch, Harald, 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 | English |
| Type | Thesis |
| Format | 1 v. : col. ill. |
| Rights | Stellenbosch University |
Page generated in 0.0029 seconds