Separation of Ethylene‐Propylene Copolymers by Crystallization and Adsorption Mechanisms. A Journey Inside the Analytical Techniques

Summary The separation of polyolefin copolymers in terms of composition has been typically performed by crystallization techniques. In the last years, a new liquid chromatography approach has become available that extends the range of composition analysis applicable towards higher comonomer content. Every technique has its capabilities and limitations, and the use of multiple hyphenated techniques is often required to provide unequivocal results for characterizing the microstructure of complex copolymers like high impact polypropylene. A good understanding of the individual separation mechanisms is essential to interpreting the obtained results properly, and this becomes a challenging task when dealing with ethylene‐propylene copolymers or homopolymer blends. The separation of these resins by the existing techniques is discussed. The role of solvent and the adsorbent in the separation mechanisms is investigated and a comparison of crystallization and liquid adsorption chromatography with various types of adsorbents is presented.