Fractionation and Characterisation of Propylene‐Ethylene Random Copolymers: Effect of the Comonomer on Crystallisation of Poly(propylene) in the γ‐Phase

Abstract

Summary: Three propylene‐ethylene random copolymers, of varying ethylene content, were fractionated using preparative TREF. The TREF fractions were subsequently analysed offline by CRYSTAF, DSC, 13C NMR spectroscopy, HT‐GPC, and WAXD. The effect of the ethylene comonomer on the crystallisability of the propylene was investigated, along with the effect of the comonomer on the type of crystal phase formed during the crystallisation. The results show that the comonomer inhibits the crystallisation of the copolymer and that as the ethylene content increases, the crystallisation and melting points decrease. It was also shown that the higher the ethylene content, the more of the γ‐phase crystal type is formed. The inter‐molecular distribution of the ethylene comonomer and stereo errors vary between the samples analysed, and this accounts for the relative differences in crystallisation behaviour of the samples.13C NMR of propylene‐ethylene random copolymer.magnified image13C NMR of propylene‐ethylene random copolymer.

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

“…If a detailed analysis of a sample is required, TREF is used to prepare 7-15 fractions and each fraction is then individually characterized by FTIR, SEC, NMR, and DSC. [22][23][24][25][26][27] Moreover, TREF may be coupled online with SEC analysis. 14,[28][29][30] These time and labor consuming analytical procedures could be partially eliminated by the use of a liquid chromatographic separation according to chemical composition or microstructure.…”

Recent Advances in High-Temperature Fractionation of Polyolefins

“…They argued that the hyphenation of TREF with NMR provided a wealth of information and insight into the microstructure of the polymers that was not possible otherwise. Harding and van Reenen [26] fractionated three propylene-ethylene random copolymers by using P-TREF and analyzed the fractions by CRYSTAF, DSC, 13 C NMR, HT-SEC and WAXD. It was shown by them that comonomer incorporation inhibits the crystallization of the copolymer and as the ethylene content increases, the crystallization and melting point decreases.…”

Crystallization behavior and mechanical properties of nano-CaCO3/β-nucleated ethylene-propylene random copolymer composites

“…Accordingly, random copolymers of propylene with a low amount of 1-olefins such as ethylene, 1-butene, 1-hexene and 1-octane are synthesized. Among these copolymers, ethylenepropylene random copolymer (PPR) has received a great deal of attentions owing to its higher impact strength than isotactic PP [1]. It has been used for making pipes, plates, domestic appliances and automobiles.…”