PVDF Nano Composite Coatings Resistant to Ionizing Radiation

Rahmani, Peyman | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41444 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and petroleum Engineering
  6. Advisor(s): Forounchi, Massoud; Dadbin, Susan
  7. Abstract:
  8. Poly (vinylidene Fluoride) (PVDF)/organoclay nanocomposite films were prepared via melt mixing, solution casting and Co-precipitation techniques. The effects of different kinds of nanoclay, sample preparation techniques and electron beam irradiation on PVDF/Nanoclay nanocomposite are reported in this research project. Differential scanning calorimetry was used to study thermal properties and crystallinity of the PVDF and its nanocomposites. The chemical and crystalline structure of the samples was analysed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) and the mechanical properties of the PVDF nanocomposite were characterized by stress strain test. The degree of crosslinking was evaluated by gel content measurements. The results obtained from XRD patterns displays intercalation or exfoliation morphologies depending on the preparation methods and/or nanoclay type. The solvent cast samples showed phase separation or intercalation depending on the organic modifiers while exfoliation was observed in the films obtained by Co-precipitation method. An intercalated morphology was observed in the nanocomposite films prepared by the melt blending method. The crystalline structure of the PVDF characterized by FTIR spectra and XRD patterns exhibited only alpha crystals whilst introducing the organically modified clays promoted formation of β-crystals regardless of the nanoclay type. This is also consistent with the DSC results which display higher melting and crystallization temperature in the nanocomposite films as the β-crystals have higher T_m and T_c. Degree of crystallinity decreased with incorporation of small amounts of nanoclay suggesting the confinement effect of the nanoclay sheets lowers the total crystallinity of the PVDF. A three dimensional network was performed upon exposing the neat PVDF and its nanocomposites to electron beam irradiation in the dose rang from 100 to 500 kGy. The gel content increased with increasing the radiation dose up to 500 kGy though all nanocomposites showed lower crosslinking density compared to the neat PVDF implying the inhabitation of chain movement. The results obtained from stress-strain test showed enhancement of the yield stress with increasing the nanoclay content and irradiation dose up to 300 kGy. The E-modulus of the nanocomposites also increased with increasing the nanoclay content and irradiation dose
  9. Keywords:
  10. Nanocomposite ; Electron Beam ; Crosslinking ; Nanoclay ; Polyvinylidene Fluoride (PVDF)

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