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Zheng Zhou Thesis - ETD Ohio Link.pdf (4.33 MB)

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DIELECTRIC PROPERTIES OF MULTILAYER POLYMER FILMS FOR HIGH ENERGY DENSITY CAPACITORS & PREDICTING LONG-TERM CREEP FAILURE OF A BIMODAL POLYETHYLENE PIPE FROM SHORT-TERM FATIGUE TESTS

Zheng, Zhou
http://rave.ohiolink.edu/etdc/view?acc_num=case1369331821

Abstract Details

2013, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Part A: An approach of “forced assembly” multilayer coextrusion was used to produce alternately layered polymeric films for high energy density capacitor applications. The breakdown fracture mechanisms have been studied extensively. Interactive crazing accompanied with delamination and fibril stretching was observed after dielectric breakdown failure. The fracture mechanisms study give us some hint that the adhesion between Polycarbonate ,PC, and Poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), is not good. In order to minimize the delamination during dielectric breakdown test, and therefore improve dielectric breakdown properties, an “interphase modification” technique--modifying the interphase between PC and P(VDF-HFP) through introducing a third tie layer--was introduced. The newly designed three component dielectric films (ATBTATBTA, A-PC, B-P(VDF-HFP), T-PMMA) exhibited a 50% enhancement in energy density, 40% decrease in hysteresis, and orders of magnitude slower ion migration relative to the two component control. These property improvements are mainly attributed to the localized interactions at PMMA/P(VDF-HFP) and PMMA/PC interfaces, forming interphase regions. The modified PMMA/P(VDF-HFP) interphase region can effectively hinder the migration of impurity ions in P(VDF-HFP), reducing their mobility within the layer. In addition to fracture mechanisms study, the long-term dielectric lifetime was probed using homemade setup and it was found out that the layered films of PC/P(VDF-HFP) can have up to 1000X longer lifetime relative to simple PC and P(VDF-HFP) blend films. Part B: The so-called third generation of polyethylene pipe resins provides exceptional improvements in environmental stress crack resistance, resistance to rapid crack propagation and creep resistance compared to earlier generations. Short term fatigue testing was used to predict long term creep failure of a bimodal polyethylene (BMPE) pipe with superior creep resistance. The fatigue failure time can be substantially shorter than the failure time in standard creep tests especially for resins that exhibit a high resistance to slow crack growth. This study was undertaken to determine whether a fatigue-to-creep correlation is applicable to the new generation BMPE pipe resins, and to ascertain whether a lifetime prediction can be obtained within a reasonable time period. The stepwise mechanism of fatigue crack propagation at 50 °C was verified and the crack growth rate was related to the maximum stress and R ratio by a power law relation. The temperature dependence of slow crack growth followed an Arrhenius relation with a change in slope at 67 °C. The change in slope indicated that extrapolation of creep behavior at temperatures above the a-relaxation to ambient temperature requires considerable caution.
Eric Baer (Committee Chair)
Lei Zhu (Committee Member)
Donald Schuele (Committee Member)
Alex Jamieson (Committee Member)
191 p.
Engineering

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Citations

  • Zheng, Z. (2013). DIELECTRIC PROPERTIES OF MULTILAYER POLYMER FILMS FOR HIGH ENERGY DENSITY CAPACITORS & PREDICTING LONG-TERM CREEP FAILURE OF A BIMODAL POLYETHYLENE PIPE FROM SHORT-TERM FATIGUE TESTS [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1369331821

    APA Style (7th edition)

  • Zheng, Zhou. DIELECTRIC PROPERTIES OF MULTILAYER POLYMER FILMS FOR HIGH ENERGY DENSITY CAPACITORS & PREDICTING LONG-TERM CREEP FAILURE OF A BIMODAL POLYETHYLENE PIPE FROM SHORT-TERM FATIGUE TESTS . 2013. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1369331821.

    MLA Style (8th edition)

  • Zheng, Zhou. "DIELECTRIC PROPERTIES OF MULTILAYER POLYMER FILMS FOR HIGH ENERGY DENSITY CAPACITORS & PREDICTING LONG-TERM CREEP FAILURE OF A BIMODAL POLYETHYLENE PIPE FROM SHORT-TERM FATIGUE TESTS ." Doctoral dissertation, Case Western Reserve University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1369331821

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.