Use of FT‐IR Spectrometry for On‐Line Detection in Temperature Rising Elution Fractionation

Summary: Temperature rising elution fractionation (TREF) has become a popular analytical technique that is able to determine the chemical composition distribution (CCD) of an ethylene/ α ‐olefin copolymer. An infrared (IR) detector is commonly used in TREF detection to measure the concentration of the polymer solution exiting the column as a function of elution temperature. The chemical composition of the eluting polymer at a given elution temperature can be predicted from the relationship between comonomer content and TREF elution temperature pre‐established through 13 C nuclear magnetic resonance (NMR) analysis of TREF fractions. In this article, a Fourier transform infrared (FT‐IR) spectrometer has been coupled with a TREF instrument to provide a more powerful tool for characterizing complex olefin copolymers. The Partial Least Squares (PLS) technique is used when analyzing the FT‐IR spectra of the eluting polymer solutions. The power of on‐line FT‐IR detection in TREF is demonstrated using a few complex copolymer systems, such as ethylene‐octene copolymer, polystyrene grafted ethylene‐vinyl acetate copolymer and ethylene‐methyl acrylate copolymer.