Master Degree / Yüksek Lisans Tezleri

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

Browse

Filters

2007 - 200922020 - 20231

Settings

Author: search.filters.author.Alsoy Altınkaya, SacideSubject: search.filters.subject.Polymers

Search Results

Now showing 1 - 3 of 3
  • Master Thesis
    Manufacturing of Starch-Based Bioplastic From Waste Potato Starch by Extrusion and Energy Analysis of the Production
    (2023) Tıhmınlıoğlu, Funda; Gökyıldız, Yasemin; Alsoy Altınkaya, Sacide; Altınkaya, Sacide; Tıhmınlıoğlu, Funda
    Plastic materials are an essential part of our daily lives and annual plastic production is higher than 380 million tons with a 4% annual increasing rate. Since the 1950s, 8.3 billion tons of plastic have been produced, 9% of these plastics have been recycled, 12% have been incinerated and the rest 79% have been dumped to landfills. Therefore, the development of biodegradable polymers obtained from renewable raw materials has become a priority to reduce the environmental impact and dependency on fossil resources. Thermoplastic starch (TPS) is a starch-based bioplastic obtained by the disruption of the starch granules with thermal and mechanical forces in the presence of plasticizer. In this thesis, production of TPS from residual potato starch by extrusion was investigated. The extrusion trials were conducted in a single-screw extruder. Glycerol was selected as plasticizer and added to starch with 20, 30 and 40 wt.%. Extrusion temperature profiles were 50-90oC, 60-90oC and 70-90oC. The pretreatment conditions for the residual starch were drying to 10 wt.% moisture content and sieving with 131μm mesh size. Specific mechanical energy values ranged between 7.89 kWhkg-1 and 43.27 kWhkg-1. The optimum product formation was selected according to processability with lower energy consumption and mechanical properties as TPS303 which has 30 wt.% glycerol content and processed between 70-90oC. Specific mechanical energy consumption for TPS303 was found to be 23.78 kWhkg-1. The mechanical properties of TPS303 were 4.48 MPa tensile strength, 59.74 MPa Young's modulus and 57.33% elongation at break. Consequently, residual potato starch was found to be a promising raw material for thermoplastic starch production with proper pretreatment.
  • Master Thesis
    Measurement and Modeling of Thermodynamic and Kinetic Data of Membrane Forming Systems
    (Izmir Institute of Technology, 2007) Arslan, Mine Özge; Alsoy Altınkaya, Sacide
    Phase inversion process involving a ternary system (nonsolvent/solvent/ polymer) isfrequently used to prepare porous and asymmetric polymeric membranes. The thermodynamic and kinetic data for the ternary system are required to understand membrane formation mechanisms, change the preparation conditions and predict the final structure of the membranes. In this study, cloud point curves for polysulfone (PSf)/1-methyl-2-pyrrolidinone (NMP)/water, PSf/tetrahydrofurane (THF)/water, PSf/NMP/ethanol, PSf/THF/ethanol, polymethyl methacrylate (PMMA)/acetone/water, PMMA/ THF/water, PMMA/acetone/formamide and PMMA/THF/formamide systems were measured by titrating polymer solutions with nonsolvents until the onset of turbidity.Binodal curves were calculated by using the Flory Huggins theory with constant interactionparameters. Theoretical ternary phase diagrams were found to be in good agreement with experimental cloud point data. In addition to liquid liquid equilibrium data, sorptionisotherms and diffusion coefficients of water, ethanol and chloroform were measured byusing a magnetic suspension balance. Results of kinetic studies have shown that water sorption in PSf films exhibits Fickian diffusion while anomalous diffusion is observed for ethanol and chloroform sorption. The kinetic data for water sorption was analyzed using a simple Fickian diffusion model to determine the diffusion coefficients. On the other hand, anamalous sorption kinetics were interpreted by a mathematical model involving independent contributions from Fickian diffusion and polymer relaxations. The model successfully fits non-Fickian anomalies including sorption overshoot and allows to determine diffusion coefficients and relaxation times. Diffusivities of penetrants in PSf was found to decrease in the following order: Water > Chloroform > Ethanol. Equilibrium sorption isotherms of ethanol and chloroform are well described by classical Flory Huggins thermodynamic theory with constant interaction parameters. A modified version of this theory for concentration dependent interaction parameter is used to correlate the sorption isotherm of water. Vrentas Duda free volume theory is able to correlate diffusivity data of water collected at 30 C and 40 C while the theory fails to correlate the diffusivities of ethanol and chloroform both of which were determined from diffusion-relaxation model.
  • Master Thesis
    Preparation and Characterization of Antimicrobial Polymeric Films for Food Packaging Applications
    (Izmir Institute of Technology, 2007) Gemili, Seyhun; Alsoy Altınkaya, Sacide
    In this study, cellulose acetate (CA) based antimicrobial packaging materials containing lysozyme as an antimicrobial additive were developed. In order to achieve appropriate controlled release of antimicrobial agent, the structure of the films were changed from highly asymmetric and porous to dense ones by modulating the composition of the initial casting solution. The effectiveness of the films were then tested through measurement of soluble and immobilized lysozyme activity, release kinetics and antimicrobial activity on selected microorganisms. The highest release rate, soluble lysozyme activity and resulting antimicrobial activity (on E.coli) was obtained with the film prepared from 5 % CA solution including 1.5 % lysozyme. Increasing CA content in the casting solution decreased the porosity of the films, hence, reduced the release rate, maximum released activities and the antimicrobial activities of the films. On the other hand, immobilized activities and the tensile strength of the films increased. The mechanical properties of the antimicrobial films cast with 5 % and 10 % CA were similar to those of lysozyme free CA films. However, significant reductions in tensile strength and elongation values were observed for the antimicrobial films prepared with 15 % CA. Differences in the release rates, soluble, immobilized and antimicrobial activities at porous and dense surfaces of the films suggest that different surfaces of CA films can be employed for antimicrobial packaging according to the targeted shelf-life of the food products. When the films made with 5 % CA were stored at 4 °C for a maximal period of 105 days, an increase in soluble lysozyme and antimicrobial activities of the films were observed. The results demonstrate that CA films prepared in this study show promising potential to achieve controlled release in antimicrobial packaging.