Characterization of ethylene-propylene copolymers with high-temperature gradient adsorption liquid chromatography and CRYSTAF



Blends of linear polyethylene (PE) and isotactic polypropylene (iPP) with different average molar masses and a series of ethylene-propylene (EP) copolymers with different chemical composition as well as blends of PE, Ipp, and EP copolymers were separated using a carbon-column packing (Hypercarb®) and gradients of 1-decanol or 2-ethyl-1-hexanol → 1,2,4-trichlorobenzene (TCB). The separation is based on full adsorption of linear PE on the carbon sorbent at temperature 160°C. However, iPP is not adsorbed and elutes in size exclusion mode. The random EP copolymers have been adsorbed in the column packing and separated according to their average chemical composition after application of the gradient starting with alcohol and ending with pure TCB. The elution volumes of the copolymers depended linearly on the average concentration of ethylene in the copolymers. The HPLC elution profiles were correlated with the CRYSTAF elution profiles. In contrast to CRYSTAF, fully amorphous polyolefin samples were separated with the high-temperature adsorption liquid chromatography. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011