Polymerization Kinetics of Ethylene/1-Hexene Copolymers Made with Two Metallocene Catalysts

• Author / Creator

  Saadat, Sahar

• Polyolefins account for the largest portion of the world’s plastics production. Increasing demands on the performance of polyolefin products require that we keep advancing our understanding of these ubiquitous plastics. Polymerization conditions and catalyst types have a marked influence on polyolefin microstructure which, in turn, determines their final application properties. The polyolefin industry is starting to use two metallocene catalysts to make polyolefins with controlled microstructures for advanced applications. Having a detailed knowledge of the polymerization kinetics of each individual catalyst is essential to control the microstructures of polymers made with these dual catalysts systems. An important question that needs to be answered is: if we know how each catalyst work alone, can we predict their behaviour in a binary mixture? In this research project, the solution polymerization kinetics of ethylene and 1-hexene with two metallocenes, constrained geometry catalyst (CGC-Ti) and bis(cyclopentadienyl)-zirconium (IV) dichloride (Cp2ZrCl2), were investigated in a semi-batch reactor. The factors studied were: 1) ethylene/1-hexene ratio, 2) hydrogen/ethylene ratio, 3) methylaluminoxane (MAO) concentration, 4) catalyst concentration, and 5) MAO/catalyst ratio. Mathematical models to describe the polymerization kinetics with each catalyst were developed using experimental polymerization and polymer characterization results. These models were then used to predict the behaviour of binary mixtures of the individual catalysts. The polymerization kinetics of the binary system could be described as a linear combination of the individual polymerization kinetics of CGC-Ti and Cp2ZrCl2. The molecular weight distribution (MWD) and short chain branch distribution (SCBD) of the copolymers made with the dual catalyst could also be predicted from the equivalent distributions for copolymers made with the individual catalysts. The proposed approach allows us to predict the properties of polyethylenes made with dual catalysts, which is an important requirement when developing polyolefins for advanced applications.

• Subjects / Keywords

  • Polymerization Kinetics
  • Metallocene Catalysts
  • Kinetic Modeling

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3639KM27

• 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.