Preparative TREF ‐ HT‐HPLC ‐ HPer DSC: Linking Molecular Characteristics and Thermal Properties of an Impact Poly(propylene) Copolymer

Abstract

Summary:The microstructure and thermal behaviour of complex polyolefins affect the product properties significantly. Therefore a thorough characterization of such semi-crystalline materials is necessary to understand the relationship between molecular structure and melting and crystallization behaviour. In the present work, the correlation between the chain structure and thermal behaviour of various components in a complex midelution temperature TREF fraction (80 C) of a commercial impact poly(propylene) copolymer were studied by using a combination of prep TREF and a highly selective separation method, HT HPLC, followed by thermal analysis of resulting dual fractions via a fast scanning DSC technique (HPer DSC). HT-HPLC can separate polymer chains according to their microstructure (chemical composition, tacticity and chain branching) within in short analysis time. The ability to measure the thermal properties of minute amounts of materials by HPer DSC helps to correlate their chemical structure with the melting and crystallization behaviour. In this way, the present hyphenated technique (prep-TREF-HT-HPLC-HPer DSC) provides a powerful tool to separate and analyse complex mixtures of polymer components having different chemical structures and thermal properties.

Molecular heterogeneity of ethylene-propylene rubbers: New insights through advanced crystallization-based and chromatographic techniques

“…DSC is a simple and widely used method, however, the crystallization behavior is strongly influenced by the thermal history of the sample . Solution crystallization‐based techniques, such as temperature rising elution fractionation (TREF) and crystallization analysis fractionation (CRYSTAF), have been utilized to analyze CCD of EPR copolymers with high ethylene contents. It has been indicated by both techniques that these copolymers are completely amorphous or contain only very small amounts of crystallizing material.…”

“…The recently developed high temperature–high performance liquid chromatography (HT‐HPLC) allows the analysis of both the amorphous and the crystalline fractions since the separation depends on the interaction or adsorption of the macromolecules with the stationary phase . For EPR copolymers it had been reported that on a graphitic stationary phase the separation depends mainly on the ethylene content of the sample . The HPLC chromatograms of EPR copolymers with high ethylene contents had shown multimodal elution profiles that indicate the complexity of these samples .…”

Liquid Chromatography at Critical Conditions of Poly(propylene)

“…Thus, by using a combination of LCCC and pure desorption promoting solvent both constituents of hiPP could be baseline separated and detected. In difference to the previously described HPLC systems for the separation of hiPP, which required gradient elution (1‐decanol→TCB or n‐decane → TCB, the HPLC system described here uses two eluents (2‐octanol/ODCB and ODCB) at constant composition.…”