Fractionation of Ethylene/1-Octene Copolymers by High-Temperature Thermal Gradient Interaction Chromatography

Abstract

High-temperature thermal gradient interaction chromatography (HT-TGIC) was recently introduced into the area of polyolefin analysis. This new technique uses commercially available Hybercarb columns to separate polyolefin chains based on their interaction with the porous graphitic carbon stationary phase in a temperature gradient mode. In this paper, a systematic study of HT-TGIC operation conditions is presented for ethylene/1-octene copolymers and their blends. One of the objectives of this investigation is to identify the best set of conditions that maximize peak separation of copolymers in a binary blend. Although the chromatograms of individual resins and their blends are independent of the cooling rate, it will be shown that sample volume (column loading) and heating rate during the elution cycle affect the peak separation of the components in binary blends.

Effect of Solvent Type on High‐Temperature Thermal Gradient Interaction Chromatography of Polyethylene and Ethylene–1‐Octene Copolymers

“…In the figures below, the upper and lower temperatures used in the cooling cycle are indicated between square brackets, for instance, [155–90 °C]. The detailed description of the experimental work was explained in our previous publication . In this previous study, heating rate (HR) and sample size (SZ) were found to be the most important operational conditions affecting HT‐TGIC profiles of individual resins and their blends.…”

“…The effects of the operating conditions on HT‐TGIC profiles were investigated in our recent study . The results of this study indicated that the chromatograms of individual resins and their blends were independent of the cooling rate.…”

Chemical Composition Fractionation of Olefin Plastomers/Elastomers by Solvent and Thermal Gradient Interaction Chromatography

“…For EP rubbers as well as for PP‐EPR reactor blends, TGIC remains insensitive for some compositions even if improved experimental protocols are applied. It will be interesting to see if a change in mobile phase broadens the accessible ethylene content range . This will be the subject of forthcoming investigations and will be of significant interest due to the fact that all industrially relevant EP rubbers have comonomer contents below 60 mol% ethylene.…”

“…As an alternative, thermal gradient interaction chromatography (TGIC) has been introduced where a single solvent is used as mobile phase enabling the usage of various detectors such as infrared (IR), light scattering (LS), and online viscometer . This method has been used extensively for the chemical composition analysis of LLDPE . While SGIC operates at temperatures above melting, and thus, sample crystallinity does not influence the fractionation process, TGIC uses a temperature gradient starting at ambient temperature.…”

“…While SGIC operates at temperatures above melting, and thus, sample crystallinity does not influence the fractionation process, TGIC uses a temperature gradient starting at ambient temperature. At this temperature, most sample components have crystallized or precipitated onto the stationary phase, and a mixed fractionation mechanism may take place in the elution process during the heating ramp . To determine the application ranges for both methods, it would have been necessary to fractionate the same sample set by SGIC and TGIC, which has never been done and it is addressed in this study.…”