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Impermeability of Oxygen in Passive/Active Polyethylene Nanocomposite Films

Khederlou, Khadijeh | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51702 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Bagheri, Reza; Shojaei, Akbar
  7. Abstract:
  8. In this study, polyethylene films made of LDPE / LLPE / reinforced with mechanical barrier of clay and reactant of iron nanoparticles were made in their optimal combination and necessary improvements were made on them. Investigations show that, independent of volume fraction, the addition of spherical nanoparticles does not have much effect on reducing the polymer matrix’s permeability. In nanocomposites containing cylindrical particles, for considerable reduction of the permeability, over 20 volume percent of nanoparticles it is required, while in platelet nanoparticles, less than 10% vol is sufficient. In clays with modifier concentration above the cation exchange capacity, there is less space for polymer entry between the clay plates during the process of mixing, and it can be said that the values of the larger initial intervals are not necessarily appropriate for better distribution of nanoclay. The use of a polymer compatibilizer having a higher Tc can have a more stimulating nucleation effect on the matrix.On the other hand, grafting with MA groups increases the thickness of the crystals. The presence of the compatibilizer in the interface is more likely and accelerates the crystallization of both components. The part of the compatibilizer has a nucleation role and the other part enters the crystalline structure of the same component in the field and increases the thickness and amount of the crystals. The effect of the compatibilizer on accelerating crystallization depends on the crystallization temperature of the desired component and the effect on the nucleation rate depends on the component similar to the polymeric part of the compatibilizer. Also, in the absence of the compatibilizer, a slight dispersion occurs and the surface of the dispersed stacks can also play a role of nucleation. When the content of the compatibilizer increases in the nanocomposite, its tendency for separation from the matrix increases and its nucleation effect goes beyond the nucleation of the optimal dispersion of nanoclay. For a nanoclay concentration of between 1% and 5% by weight, the optimal concentration of the compatibilizer is 3-5% by weight. The presence of low weight nanoclay (below 5% by weight) can reduce the permeability of polyethylene film by 76% while by modifying the surface and spacing of the nanoclays with iron nanoparticles, this additive will be able to reduce the permeability to oxygen by 84%. Finally, an attempt has been made to present a model of the simultaneous effect of these factors on reducing permeability
  9. Keywords:
  10. Gas Permeability ; Oxygen ; Nanocomposite ; Nanoclay ; Low Density Poly Ethylene(LDPE) ; Polyethylene-Clay Nanocomposite Film ; Iron Nanoparticle

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