Enhanced characterization of the chemical structure of high-density polyethylene by size exclusion/thermal fractionation on poly(styrene-co-divinylbenzene) columns

Abstract

Following the recent trends in polymer analysis, a novel fractionation method was developed using xylene as an alternative to trichlorobenzene (TCB) and offering a more exhaustive characterization of the chemical structure of high-density polyethylene (HDPE). The method is based on a linearized evaporative light scattering detector (LinELSD), which has a much better signal-to-noise for the solutions of HDPE in xylene, as compared with the traditional differential refractive index (DRI) and infrared (IR) detectors. The low viscosity of xylene opens the possibility to use the poly(styrene-co-divinylbenzene) (PS-DVB) columns not only for gel permeation chromatography (GPC) but also for temperature-rising elution fractionation (TREF). An immediate application is the simultaneous measurement of the wax fraction’s content and molecular weight (MW) in HDPE. Furthermore, there are strong indications that the thermogram profile corresponding to the isothermal extraction at 70 °C provides a fingerprint of the HDPE synthesis catalyst.