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Influence of the short‐chain branch length on the calibration of temperature rising elution fractionation systems
Author(s) -
Savitski Edward P.,
Caflisch George B.,
Killian Christopher M.,
Meadows Michael D.,
Merkley Joseph H.,
Huff Brenda J.
Publication year - 2003
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.12688
Subject(s) - elution , branching (polymer chemistry) , fractionation , calibration curve , ethylene , chromatography , analytical chemistry (journal) , copolymer , calibration , materials science , polyolefin , chemistry , olefin fiber , catalysis , organic chemistry , polymer , mathematics , statistics , layer (electronics) , detection limit
The effects of short‐chain branch (SCB) length on the calibration of temperature rising elution fractionation (TREF) were examined. Samples of ethylene–hexene, ethylene–octene, and a novel polyolefin produced using Eastman Chemical Company's Gavilan catalyst technology were used to prepare TREF calibration curves. Preparative TREF was used to collect fractions of the materials based on their crystallizability, and the branching frequencies of the fractions were determined by NMR. Calibration curves were generated by plotting the branching frequency as a function of the TREF elution temperature. The results indicate that the calibration curves shift to lower TREF elution temperatures as the length of the SCB increases from methyl to butyl to hexyl. Other factors that may contribute to this shift include chain microstructural differences from variations in catalyst structure and process conditions. The shift can be decreased by plotting the data in “number of branches per 1000 backbone carbons” versus TREF elution temperature instead of the more traditional “number of branches per 1000 total carbons.” These data indicate that the branch type must be known a priori to calculate SCB averages and SCB distributions and that unique calibration curves exist for copolymers made using different α‐olefin comonomers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 722–728, 2003