NMR onderzoek naar de moleculaire structuur en dynamica van ethyleen-propyleen copolymeren

Abstract

Commercial ethylene-propylene copolymers have improved properties over polypropylene, polyethylene and their blends. These heterophasic copolymers are synthesised by adding ethylene during the second stage of the polymerisation process of polypropylene. Until now the characteristics of the synthesised polymer can be checked in the laboratory only after the polymerisation. This takes quite some time however. It would be more economic to check the product directly during the polymerisation. The question that came from the industry was: should it be possible to control the polymerisation with an on-line industrial NMR? To introduce such a NMR in the production process, the NMR results of the et hylenepropylene copolymers have to be clearly understood and a detailed solid-state NMR study of the complex polymer is needed. For this study, a few ethylene-propylene heterophasic copolymer samples were supplied by Borealis. All the samples contain less than fifteen percent of ethylene as is typical for such copolymers. Although it is a small range of ethylene content the copolymers can have very different macroscopic properties. It is not only important how much ethylene the polymer contains, but also how the ethylene is divided among the polypropylene chains and this can be studied with liquid-state NMR. In addition, with solid-state NMR it is possible to study the molecular mobility of the polymer chains which can be correlated with the macroscopic properties. The purpose of this research was to investigate the ethylene-polypropylene copolymers (supplied by Borealis) with NMR to get a better understanding of the molecular structure and molecular dynamics of the copolymers so that the results of an industrial NMR can be interpreted correctly.