Characterization of molecular properties of propylene impact copolymers

Pretorius, Marius Stefan (2007-03)

Thesis (MSc) -- University of Stellenbosch, 2007.

Thesis

ENGLISH ABSTRACT: This study involves the fractionation and characterization of five propylene impact copolymers as well as the use of preparative temperature rising elution fractionation (prep-TREF) to study batch consistency. The fractionation technique used in the study was prep-TREF. The prep-TREF fractions were subsequently analysed off-line by crystallization analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC), 13C nuclear magnetic resonance {1 3 C NMR) and high-temperature gel-permeation chromatography (HT-GPC). The molecular heterogeneity of these copolymers was illustrated, while optimizing the fractionation technique. Also propylene impact copolymers that seem similar, as well as obviously different in molecular make-up, were compared to illustrate batch consistency. The results for the original polymers show that the ethylene content, as determined by 13C NMR, was significantly different from that claimed by the manufacturers. CRYSTAF analyses indicated differences between two seemingly similar polymers from different batches. The prep-TREF technique was optimized for these materials, particularly with respect to the elution temperatures and temperature intervals of these materials. Up to 15 clearly identifiable fractions, of which 7 comprised about 90 % of the total weight of the polymer fractionated, were obtained. Three major components were isolated from each of the polymers. These were ethylene-propylene-rubber, EPR, (50 - 60 mole %), propylene homopolymer and ethylene-rich copolymers. The EPR was non-crystalline and largely present in the fractions isolated at elution temperatures of 25 and 50 °C. Most of the ethylene in the copolymers is present as EPR. An increase in the ethylene content does correspondingly increase the rubbery, soluble part of the polymer. PrepTREF was shown to be a useful technique to compare very complex materials such as the propylene impact copolymers.

AFRIKAANSE OPSOMMING: Hierdie navorsing behels die fraksionering en karakterisering van vyf propileen impak kopolimere, sowel as die gebruik van preparatiewe temperatuutstyging eluering fraksionering (prep-TREF) om bondel ooreenstemming the bestudeer. Die fraksionerings tegniek wat gebruik is in die navorsing is prep-TREF. Die prep-TREF fraksies was geanaliseer deur kristallisasie analise fraksionering (CRYSTAF), differensiele skandeer kalorimetrie (DSC), 13C kem magnetiese resonans spektroskopie ( 13C NMR) en hoetemperatuur jel-permeasie kromatografie (HT-GPC). Die molekulere heterogeniteit van die kopolimere was ook gei1lustreer, terwyl die fraksionerings tegniek geoptimaliseer was. Ook, die propileen impak kopolimere wat eenders voorkom, sowel as totaal en al verskillend is in molekulere samestelling, is vergelyk om bondel ooreenstemming te illustreer. Die resultate vir die oorspronklike polimere het gewys dat die etileen inhoud, soos bepaal deur 13C NMR, verskil het van dit wat die vervaardigers aanspraak op maak. CRYSTAF analise het verskille opgelewer tussen twee oenskynlik eenderse polimere van verskillende bondels. Die prep-TREF tegniek is geoptimaliseer vir hierdie materiale, veral met respek tot die elueringstemperatuur sowel as die temperatuur intervalle van die materiale. 15 duidelike onderskeibare fraksies, waarvan 7 ongeveer 90 % van die totale gewig van die polimeer wat gefraksioneer is opmaak, is verkry. Drie vemame komponente is gei"soleer. Dit is 'n etileen-propileen-rubber, EPR, (50 - 60 mol %), propileen homopolimeer en etileen-ryke kopolimere. Die EPR is nie-kristallyn en grootendeels teenwoordig in die 25 en 50 °C fraksies. Meeste van die etileen is in die kopolimere teenwoordig as EPR. 'n Toename in die etileen inhoud ly gevolglik tot 'n toename in die rubberige, oplosbare deel van die polimeer. Prep-TREF is bewys as 'n nuttige tegniek om baie kompleks materiale soos hierdie propileen impak kopolimere te vergelyk.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/50695
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