Studies on the use of filter-based IR detector for short-chain branching characterization of polyolefin copolymers with high temperature size exclusion chromatography

Abstract

Even though polyolefins are simple polymers from chemical structure point of view, their full characterization in practice is still an intriguing task. Basic macromolecular characteristics of polyethylene or polypropylene like molar mass moments and their distributions (MMD) but also chain conformation and thus information on long-chain branching, can be addressed with high-temperature size-exclusion chromatography (HT-SEC). Hyphenation of infrared detection to size-exclusion chromatography expands possibilities of SEC even more and allows to reveal comonomer incorporation across molecular weight and thus help in the study of catalytic systems used in polyolefin synthesis.Multiband filter-based infrared detector gives an easy and fast access to so-called short chain branching distribution (SCB) vs MMD by coupling to HT-SEC. In our previous work [31], we summarize recent findings on application of a filter-based detector towards characterization of polyolefins synthesized with different catalytic systems and varying comonomer types. In this work, an influence of the comonomer type on the detector calibration line is elaborated. Statistical evaluation of different calibration lines is discussed in detail. Based on this evaluation practical aspects of filter-based IR detectors calibration are mentioned. Finally, numerical computer simulations can predict how much calibration lines deviate from linearity based on the spectra of the polymer and on the bandwidth of the detector filters.