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High-Temperature Thermal Gradient Interaction Chromatography (HT-TGIC) of Polyolefins: Effect of Polymer Molecular Weight, Comonomer Fraction, and Comonomer Type

  • Author / Creator
    Amirreza Badri
  • Polyolefins are the most important commodity polymers today. The demand for polyethylene and
    polypropylene, the two most important polyolefins, has been increasing steadily since their
    discovery in the late fifties.
    The properties of polyolefins is defined by their distributions of molecular weight (MWD),
    chemical composition (CCD), and long chain branching (LCB). The MWD is measured by hightemperature gel permeation chromatography (GPC). Several crystallization-based techniques,
    such as temperature rising elution fractionation (TREF), crystallization analysis fractionation
    (CRYSTAF), and crystallization elution fractionation (CEF), are used to measure the CCD of
    polyolefins. They are time consuming, prone to co-crystallization artifacts, and limited to lower
    comonomer fractions (< 15 mol%). High-temperature solvent gradient interaction chromatography
    (HT-SGIC) can also be used to measure the CCD of polyolefins and does not suffer from the
    limitations of crystallization-based methods, but it unfortunately uses two solvents (good/bad
    solvent) and non-quantitative evaporative light scattering detectors. A newly introduced technique,
    high-temperature thermal gradient interaction chromatography (HT-TGIC), is an attractive
    alternative because of its short analysis time and wide range of comonomer fractions. In addition,
    HT-TGIC uses only one solvent and can be combined with regular chromatographic detectors such
    as infrared detectors, refractometers, viscometers, and light scattering detectors.
    Previous HT-TGIC investigations were mostly limited to ethylene/1-octene copolymers with
    number average molecular weights (Mn) higher than 25 000. For these samples, Mn does not affect
    HT-TGIC fractionation, and peak temperatures display an inverse linear relation with comonomer
    fraction.
    ii
    The main objective of this thesis was to determine empirical calibration curves relating peak
    temperature to polymer Mw, comonomer fraction, and comonomer type using a set of ethylene/-
    olefin copolymers with Mn < 25 000 and different comonomer types (1-hexene, 1-octene, and 1-
    decene). The complementary objective of this thesis was to develop a new packing material for
    HT-TGIC columns. Conventional HT-TGIC columns are filled with porous graphite particles,
    which may have lower resolution due to size exclusion effects. The proposed novel packing
    material consisted of non-porous silica particles covered with graphene (GNPSi) to reduce size
    exclusion effects.

  • Subjects / Keywords
  • Graduation date
    Spring 2021
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-ky86-t031
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.