Polymerization Kinetics and Structure-Property Relationships of Ethylene/1-Hexene Copolymers

• Author / Creator

  Caldera Palacios, Anuar Alfonso

• Polyethylene accounts for 32% of the world’s plastics production and it is continuing to grow for the foreseeable future. Its versatility to modify its molecular structure using different types of catalyst or modifying the reaction conditions makes polyethylene suitable for a wide range of applications resulting in large advantages in plastic production for the last 50 years.

  However, polyethylene still faces new challenges. Combining the knowledge of the catalyst package and the production process is required for new breakthroughs to occur for further development and optimization of polyethylene production and quality. In this research project, the polymerization kinetic of metallocene catalyst will be investigated and a model for structure-property relationship will be proposed to contribute with the knowledge of the catalyst package.
  The solution polymerization kinetics of ethylene and 1-hexene with the metallocene catalyst Bis(cyclopentadienyl) hafnium(IV) dichloride was investigated in a semi-batch reactor. The polymerization kinetics were studied; modifying the following variables: Hydrogen/ethylene ratio, ethylene/1-hexene ratio, reaction temperature, and ethylene concentration. Later, reaction mechanisms and mathematical models were proposed using the experimental data to explain the uptake ethylene curves and polymer characterization results. The mathematical models developed will help to predict the polymer structure at different reaction conditions.

  Additionally, a model to correlate polymer structure with its mechanical properties was proposed. The model includes the Molecular Weight Distribution (MWD) and the Short Chain Branching Distribution (SCBD) of the polymer obtained by Cross Fractionation Chromatography (CFC). The model will predict a Primary Structure Parameter (PSP) that correlates with several mechanical properties of the polymer. Thus, if the polymer structure is known, the mechanical properties could be estimated or if a specific mechanical property is desired, the possible polymer structure needed can be estimated.

  Finally, the kinetic model and the mechanical properties were integrated to predict the mechanical properties of the polymer from reaction conditions. Thus, it can be simulated how the mechanical properties are affected when a variable in the reaction condition changes (i.e. when several catalysts are mixed in the reactor). This integration would help to obtain a starting point in the development of new grades, cutting time and resources.

• Subjects / Keywords

  • Kinetics
  • Mechanical properties
  • Polyethylene

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R30000G3K

• License

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