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

Olefin plastomers/elastomers are typically copolymers with high comonomer contents and low crystallinities. Therefore, the fractionation of these materials with crystallization‐based methods is not feasible. On the other hand, solvent and temperature gradient interaction chromatography (SGIC and TGIC, respectively) are suitable techniques for the separation of olefin copolymers with regard to their chemical composition. In this study, the application ranges of both techniques are investigated and compared for ethylene–propylene (EP) copolymers. A linear dependency of ethylene content versus elution volume is obtained with SGIC in practically the whole ethylene range. In the case of TGIC, a linear dependency is obtained within certain ethylene content limits. The accessible ethylene content separation range for TGIC is 50–100 mol% ethylene, and a broader 26–100 mol% ethylene range is accessible for SGIC, the latter being the technique of choice in the analysis of EP rubbers. Temperature and solvent gradient interaction chromatography are shown to be useful methods for the chemical composition fractionation of complex ethylene–propylene copolymers. The accessible comonomer ranges are 50–100 mol% ethylene for temperature gradients while with solvent gradients the complete comonomer range of 0–100 mol% ethylene can be addressed.