Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2007 - 200912010 - 20123

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Subject: search.filters.subject.Nanocomposites (Materials)

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Now showing 1 - 4 of 4
  • Master Thesis
    Tribological Behaviour of Polymer Nanocomposities Containing Tungsten Based Nanoparticles
    (Izmir Institute of Technology, 2007) Karal, Kazım; Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The use of nanostructured fillers in epoxy systems has a significant role on the development of thermosetting composites. Recent investigations on inorganic nanoparticles filled polymer composites reveal their significant potential in producing materials with low friction and/or high wear resistance. In the present study, epoxy nanocomposites and fiber reinforced polymer (FRP) composites were prepared with the addition of tungsten based nanostructured particles which are produced by mechanical alloying. The effects of the nanostructured additives on the tribological, mechanical and thermal properties of composite laminates and nanocomposites were investigated. Composite laminates with and without filler were manufactured by using hand lay-up technique and cured under compression. It was found that tungsten based particle loading has no significant effect on the flexural properties of the nanocomposites and the composite laminates, and the tensile properties of the nanocomposites. It was found that while the addition of 3 wt. % of nanoparticles increases the hardness values, it significantly improves the wear resistance of nanocomposites. Furthermore, the significant improvement on the wear resistance was observed with the addition of 3 wt. % W-SiC-C (24h mechanical milling) powder onto the surface of fiber reinforced epoxy. The worn surfaces were examined with scanning electron microscopy (SEM) and the results revealed that wear mechanisms are altered due to the presence of nanoparticles in the matrix. Differential scanning calorimetry (DSC) results showed that nanoparticles have no significant effect on glass transition temperatures (Tg) of nanocomposites. Incorporation of nanoparticles increased the thermo mechanical properties of nanocomposites and composite laminates; including the storage and loss modulus and Tg.
  • Master Thesis
    Effect of Organo-Modified Clay Addition on Properties of Polyhydroxy Buttrate Homo and Copolymers Nanocomposite Films
    (Izmir Institute of Technology, 2012) Akın, Okan; Tıhmınlıoğlu, Funda; Tıhmınlıoğlu, Funda; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    As an alternative to conventional non-degradable food packaging plastics, bionanocomposites, based on bacterial biodegradable thermoplastic polyesters, poly(hydroxybuthyrate) (PHB) and poly(hydroxybutyrate-covalerate) (PHBHV) polymers incorporated with commercial organomodified monmorillonite (OMMT) were prepared by solution intercalation and melt-mixing techniques. The enhancements in barrier, mechanical, thermal, surface and optical properties of resulting nanocomposite films were evaluated as effected by OMMT concentration and preparation method. The degree of dispersion of layered silicates into polymer matrix was evaluated by X-Ray diffraction (XRD) analyses. The best level of dispersion was obtained in nanocomposites that contain 1%w/w of OMMT. However, intercalated structure was observed at higher amount of clay loaded composites. The fine delamination of OMMT in PHB and PHBHV matrix was found to be responsible for the improvements in water vapor barrier performance since more tortuous path formed for permeation of water vapor. Moreover, enhancement in mechanical and thermal properties was highly depending on the dispersion level of layered silicates which is in good accordance with structural analyses. Addition of 2%w/w of OMMT reduced the WVP of virgin films by 41.1%. Meanwhile, improvements were less significant at higher amount of clay loaded samples due to weak interaction between polymer and layered silicates. Moreover, significant improvements in mechanical properties including doubled tensile strength and 69% increase in strain at break were obtained for 2%w/w of OMMT incorporated PHB composites. In addition, significant enhancement in thermal stability, which is the major drawback of PHB films, was obtained in nanocomposites, decomposition temperature increased by 10 oC compared to pristine polymers. Moreover, addition of layered silicates into polymer matrix at low content resulted in increase in erosion rate which makes nanocomposites more eco-friendly promising alternative to conventional barrier packaging systems.
  • Master Thesis
    Fabrication of Transparent Polymer Nanocomposites Containing Pmma-Grafted Ceo2 Particles
    (Izmir Institute of Technology, 2011) Parlak, Onur; Demir, Mustafa Muammer; Demir, Mustafa Muammer; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The composite materials prepared by transparent polymer and nanosized particles possess promising future in optical design and applications since their controllable optical properties. In this study, transparent/translucent composite films based on polystyrene (PS) and poly(methyl methacrylate) (PMMA)-grafted CeO2 nanoparticles were prepared. CeO2 nanoparticles were precipitated from Ce(NO3)3·6H2O and urea in dimethyl formamide at 120°C. The surface of the nanoparticles was modified with a polymerizable surfactant, 3-methacyloxypropyltrimethoxy silane (MPS) in situ at 0°C. The size of the particles was fixed to 18 nm in diameter. The particles were dispersed into a mixture of MMA:toluene solution. The free radical solution polymerization was carried out in situ at 60°C using benzoyl peroxide (BPO) as initiator. A PMMA layer is formed around CeO2 nanoparticles. The thickness of the shell ranged from 9 to 84 nm was controlled by the amount of BPO using 6 and 0.5 wt %, respectively with respect to monomer. The layer thickness was found to be inversely proportional with the amount of initiator. The resulting PMMA-grafted CeO2 particles were blended with PS in tetrahydrofuran and the solution was spin-coat on a glass slide. CeO2 content in the composite films was fixed to 5.5 wt %. The transmission of the films was examined by UV-vis spectroscopy. The transmission of the PS composite prepared by neat CeO2 particles was 71 %. It was increased to 85 % when the composite prepared with PMMA-grafted CeO2 particles whose PMMA thickness is 9 nm. We believe that the achievement in transparency is most probably due to the reduction in refractive index mismatch between CeO2 particles and PS matrix using PMMA layer at interface.
  • Master Thesis
    Water Vapor and Gas Barrier Properties of Biodegradable Polymer Nanocomposites Films
    (Izmir Institute of Technology, 2011) Oğuzlu, Hale; Tihminlioğlu, Funda; 01. Izmir Institute of Technology
    Polylactide nanocomposite (PLANC) films were prepared with solution intercalation method by introducing sonication as an alternative for conventional polymers. The effect of polymer clay interaction on PLANCs was investigated with respect to molecular weight of the polylactide, organic modifier presence and type by focusing on five major aspects: structural analysis, barrier, thermal, mechanical and rheological properties.According to structural analyses, the best level of dispersion was obtained in PL65-10A nanocomposites due to high molecular weight polylactide and organomodified nanoclay usage leading to better molecular interaction between the layered silicates and polymer chains. However, phase separated structure was observed in PLA composites prepared with unmodified clay as basal space between layered silicates were not sufficient enough for the penetrating of the polymer chains into the layers. Barrier and mechanical properties of the nanocomposites were improved up to critical clay content for each nanocomposite system. Thermal stability of the intercalated and exfoliated nanocomposites increased with the addition of the clay. Best improvements were obtained in PL65-10A nanocomposites in accordance with structural analyses. In dynamic mechanical analysis, glass transition temperatures and storage modulus of PLANCs increased with increasing of clay amount owing to reinforcement effect of the silicate layers. In rheological measurements, PLANCs showed solid-like behavior at lower shear rates due to the formation of a network percolating clay lamellae, besides PLANCs showed shear thinning behavior at higher shear rates leading to developments on the processability of nanocomposites. Consequently, intercalated and exfoliated PLANCs could be used as an eco-friendly promising alternative to conventional polymers for short-life applications such as food packaging and coating.