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Bulk Polymerization of TPU for Reactive Processing Using Rheo-FTIR

Gadley, Jesse
http://rave.ohiolink.edu/etdc/view?acc_num=case1467805707

Abstract Details

2016, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Thermoplastic polyurethanes (TPUs) were studied to understand the complex connection between changes in rheological characteristics and reaction behavior of bulk polymerizations under flow. These materials are commonly produced using reactive extrusion (REX) where the processing equipment is used as a reactor in which the polymerizations take place. While under flow, the relationship between reaction progress, melt viscosity, and processing conditions becomes very complex leading to difficulty in targeting specific material properties and reproducibility. Generally, REX equipment is viewed as a “black box” where carefully monitored reactants are added to the extruder, are mixed in the presence of heat and shear, and the final product is then evaluated for the desired results. While these systems have been the focus of significant research effort, extending off-line experiments to processing conditions proves challenging by requiring the inference of chemical behavior from rheological measurements or vice versa. The focus of this work was to utilize simultaneous measurement of rheological behavior and Fourier transform infrared spectroscopy (FTIR) to study the connection between viscosity of the system and reaction kinetic behavior. First, an experimental technique for monitoring bulk polymerization of TPUs in situ was developed. Using this technique, the influence of hard to soft segment ratio within the TPU and the influence of shear rate on these systems was investigated. This technique was also employed to study the initial stages of polymerization and the potential influence of phase separation on the development of mechanical properties throughout the reaction. The ability to simultaneously measure changes in reactant concentration changes in time and viscosity was then used to develop a model to connect conversion and viscosity under shear flow conditions. Finally, the effect of thermal treatment on post processed materials were studied under extensional flow. After processing, exposure to temperature near the phase transition of the material resulted in changes in architecture and a subsequent change in extensional flow properties. Overall, it was determined that varying hard to soft segment composition resulted in a correlation between reaction rate, total isocyanate consumed within the system, and final properties of the system. These TPU reactions also proved sensitive to the shear rate applied due to the degree of mixing occurring during the reaction. These observations provide important benchmarks moving forward when using TPUs in reactive processing equipment. These results pave the way for future on-line studies of bulk TPU polymerization processing methods.
Joao Maia, Prof. (Advisor)
Gary Wnek, Prof. (Committee Member)
Michael Hore , Prof. (Committee Member)
Jesse Wainright , Prof. (Committee Member)
180 p.
Polymers

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Citations

  • Gadley, J. (2016). Bulk Polymerization of TPU for Reactive Processing Using Rheo-FTIR [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1467805707

    APA Style (7th edition)

  • Gadley, Jesse. Bulk Polymerization of TPU for Reactive Processing Using Rheo-FTIR. 2016. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1467805707.

    MLA Style (8th edition)

  • Gadley, Jesse. "Bulk Polymerization of TPU for Reactive Processing Using Rheo-FTIR." Doctoral dissertation, Case Western Reserve University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1467805707

    Chicago Manual of Style (17th edition)

case1467805707
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© 2016, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.