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STUDY OF PORE MORPHOLOGY AND ANISOTROPIC EVOLUTION WITH THERMAL EXCURSION OF UHMWPE FILM

ZHENG, DAZHI
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100789124

Abstract Details

2004, MS, University of Cincinnati, Engineering : Materials Science.
Porous polyolefin films are commonly used as separators in the battery industry. The thermal response of this separator membrane is critical to battery performance, particularly with regard to battery safety. Two commercial separator films (Teklon and Asahi) were studied in this Thesis. The major component of these films is ultra high molecular weight polyethylene (UHMWPE). As the temperature of the films rises above the softening point, pores collapse and ion transport ceases leading to a current shutdown. Pore morphology evolution with temperature plays very important roles in the shutdown behavior. Ultra small angle scattering (USAXS) was used to characterize pore evolution in near the softening temperature. Pore anisotropy on different length scales was measured by anisotropic ultra small angle scattering (AUSAXS). SEM images were also reported that were consistent with the USAXS analysis. The study is divided into two sections: in situ conditioning and ex situ conditioning. The in situ study covers experiments on polyelectrolyte-saturated samples thermally conditioned in the x-ray instrument. The ex situ study focused on films conditioned external to the USAXS camera and studied at room temperature in the dry state. The ex-situ conditioned dry films were observed through USAXS and AUSAXS. The data were analyzed to extract Guinier radius, Porod constant, surface area, pore chord, and solid chord in the machine direction (MD) and transverse direction (TD). Pore anisotropy evolution was measured using AUSAXS. Anisotropy at three length scales was measured by performing azimuthal scans at three different scattering angles. The Hermans orientation factor was used to make quantitative comparisons between the Teklon and Asahi materials. The results show that Teklon samples have larger pores (pore chord in MD = 1550 Å, pore chord in TD = 1400 Å) that collapse abruptly when the temperature rises above the softening temperature while Asahi films have smaller pores (pore chord in MD = 650 Å, pore chord in TD = 570 Å) that evolve more gradually with rising temperature. The AUSAXS data show that the pores of Teklon films are more anisotropic than Asahi films. Above the softening temperature, both Teklon and Asahi samples become isotropic.
Dr. Dale Schaefer (Advisor)
139 p.

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Citations

  • ZHENG, D. (2004). STUDY OF PORE MORPHOLOGY AND ANISOTROPIC EVOLUTION WITH THERMAL EXCURSION OF UHMWPE FILM [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100789124

    APA Style (7th edition)

  • ZHENG, DAZHI. STUDY OF PORE MORPHOLOGY AND ANISOTROPIC EVOLUTION WITH THERMAL EXCURSION OF UHMWPE FILM. 2004. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100789124.

    MLA Style (8th edition)

  • ZHENG, DAZHI. "STUDY OF PORE MORPHOLOGY AND ANISOTROPIC EVOLUTION WITH THERMAL EXCURSION OF UHMWPE FILM." Master's thesis, University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100789124

    Chicago Manual of Style (17th edition)

ucin1100789124
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This open access ETD is published by University of Cincinnati and OhioLINK.