Crystallization Elution Fractionation and Thermal Gradient Interaction Chromatography. Techniques Comparison

Abstract

Summary: The chemical composition distribution has been shown to be the most critical and discriminating parameter in understanding the performance of industrial polyolefins with non homogeneous comonomer incorporation. The chemical composition distribution is being analyzed by well known techniques such as temperature rising elution fractionation, TREF, crystallization analysis fractionation, CRYSTAF and crystallization elution fractionation, CEF. These techniques separate according to crystallizability and provide a powerful and predictable separation of components based on the presence of branches, irregularities or tacticity differences, independently of the molar mass. TREF, CRYSTAF and CEF can not be used, however, for the separation of more amorphous resins, and may not always provide the best solution for complex multi‐component resins due to the existence of some co‐crystallization. The application of high temperature interactive HPLC to polyolefins opened a new route to characterize these types of polymers. The use of solvent gradient HPLC for separation of polyethylene and polypropylene and the developments in HPLC on carbon based columns extended further the application of high temperature HPLC in polyolefins. A new approach has been developed recently using the carbon based column but replacing solvent gradient by a thermal gradient which facilitates the analysis of polyethylene copolymers and provides a powerful tool for the analysis of elastomers. Thermal gradient interaction chromatography (TGIC) is being compared with TREF and CEF with the analysis of model samples. The advantages/disadvantages of each technique are being investigated and discussed. The combination of TGIC and TREF/CEF provides an extended range of separation of polyolefins.

Separation of bimodal high density polyethylene using multidimensional high temperature liquid chromatography

“…Prabhu et al / J. Chromatogr. A xxx (2015) xxx-xxx in SEC of ethylene/1-alkene copolymers [14,64,[98][99][100]. Only a few IR-transparent solvents (C-H absorbance) exist: TCB, ODCB, TCE and 1-chloronapthalene.…”

Molecular Dynamics Simulation of Ethylene/Hexene Copolymer Adsorption onto Graphene: New Insight into Thermal Gradient Interaction Chromatography

“…The TGIC's main advantage over the crystallization‐based technique is its ability to separate ethylene/α‐olefin copolymers over a wider compositional range. The separation is also faster and free of co‐crystallization effects which hampers TREF, CRYSTAF, and CEF …”

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

“…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.…”