The effect of catalyst composition on the fundamental properties of isotactic polypropylene

Kleynhans, Lourens Jacob (2019-03)

Thesis (MSc)--Stellenbosch University, 2019.


ENGLISH ABSTRACT: Isotactic polypropylene is an important commercial polymer in the world today. Falling under the group of polyolefins, polypropylene serves as the largest commercial polymer worldwide together with polyethylene. Isotactic polypropylene is typically produced by a multi-sited Ziegler-Natta catalyst, the composition of which plays a critical role in the molecular properties of the final sample. The work in this study was done in order to set up a baseline of results of five different grades of isotactic polypropylene, varying in their final form (reactor powder and extruded pellet forms), as well as the catalyst composition used during polymerisation (Lynx and NHP catalysts). There were four variations possible of each different grade of isotactic polypropylene, which lead to the investigation of twenty different bulk polymer samples. Extensive analysis and characterisation was done on each of these bulk samples, as well as the fractions of each bulk sample which resulted from performing preparative temperature rising elution fractionation (p-TREF). The full analytical toolbox was implemented for the characterisation of these samples, which include SEM, DSC, HT-SEC, XRD, SSA, solution- and solid-state 13C NMR spectroscopy. By obtaining and investigating the results it was able to investigate the effect that the catalyst composition has on the fundamental properties of isotactic polypropylene samples, such as percentage isotacticity, crystallinity, molar mass, crystal structure and surface morphology. This study was performed to serve as a starting point for future projects related to these isotactic polypropylene samples investigated, such as for example the production of heterophasic ethylene propylene copolymers (HECOs). The main theme throughout this study will thus be to set up a baseline of results, for future project based on the same materials.


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