Master Degree / Yüksek Lisans Tezleri
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Master Thesis Synergistic Effect of Zinc Stearate and Natural Zeolite on Pvc Thermal Stability(Izmir Institute of Technology, 2004) Atakul, Sevdiye; Balköse, DevrimAt high temperatures (about 100 °C), PVC decomposes by the removal of hydrogen chloride (HCl) gas and the decomposition is accompanied by polymer discoloration going from yellow to orange, brown and black. In order to prevent decomposition of PVC, thermal stabilizers are added to PVC. The synergistic effect of zinc stearate (ZnSt2) and/or natural zeolite (clinoptilolite) on PVC thermal stability was investigated in this project. For this purpose PVC plastisol was prepared by mixing poly(vinyl chloride) (PVC) and dioctyphthalate (DOP) and stabilized with different amounts of metal soaps and zeolite.The materials and the prepared PVC plastisols were characterized by spectroscopic and thermal analysis techniques. The gelation of the plastisols was observed by optical microscopy and the photographs were taken by a digital camera. The complete gelation was observed at 185 °C. The morphology of PVC plastigel films were studied by scanning electron microscope (SEM). SEM with energy dispersive X-ray (EDX) analysis was used to obtain elemental compositions in polymer and particle phases. The thermal stability of PVC plastigels in terms of color were obtained by heating them in a static vaccum oven. When zeolite was used as a primary stabilizer it prevented the early blackening of the film. Kinetic study of dehydrochlorination was determined by 763 PVC Thermomat equipment for unstabilized and stabilized PVC plastigels. When PVC plastigels were heated in PVC Thermomat in the presence of nitrogen gas, the conductivity of water which nitrogen gas was passed due to the evolved HCl, changed with respect to time. The period when conductivity starts to increase is called as induction time, and the period when the conductivity value reaches to 50 uS/cm is called as stability time. The induction and stability time values of unstabilized and stabilized PVC plastigel films were obtained at 140 and 160 °C. The stabilizing effect of zeolite on the increase in the induction period of the sample was considered the result from the absorption of HCl which was thought to reduce the autocatalytic effect of HCl evolved at the initial stages of dehydrochlorination. Since the induction time of the sample having 0.53% ZnSt2 and 0.53% zeolite was higher than the PVC plastigels having only ZnSt2 or zeolite the synergistic effect on thermal stability was observed at low levels of them.Master Thesis Polyropylene - natural zeolite composite films(01. Izmir Institute of Technology, 1999) Özmıhçı, Filiz; Balköse, DevrimIn this project, preparation and characterization of polypropylene natural zeolite composites were studied. Three different series of preparation methods were performed, hot press, microscope slide, and extrusion. The composites are ranged between 0-10 wt%, 0-50 wt%, and 0-6 wt% zeolites, for hot press, microscope slide, and extrusion respectively.Polymer matrix composites are materials which contain polymers as matrix materials surrounding very small reinforcing fibers or fillers. Polymeric composites have great potential from a manufacturing standpoint and show advantages. Such as they are inexpensive, derive from natural sources, present lower density than mineral fillers, and increases the mechanical properties of the final product.In this research polypropylene was used as a matrix material and natural zeolite as a filler. Natural zeolite particles were modified with polyethylene glycol to break agglomerates and make a homogenous dispersion of natural zeolite in polypropylene matrix. These composites were characterized by using differential scanning calorimetry, thermal gravimetric analyzer, infrared spectrophotometer, optical microscopy, mechanical testing and by density measurement device. It has been found that, branched shaped air pockets existed in hot pressed and extruded composites. This causes low mechanical strength, and the densities of these films also indicate the presence of voids in the composite.Master Thesis Process Development for Metal Soaps(Izmir Institute of Technology, 2003) Gönen, Mehmet; Balköse, DevrimZinc stearate (ZnSt2) is an important compound among the metallic soaps. It has many applications e.g., in resins, paints, cosmetics, textile, lubricants and Langmuir-Blodgett films. Double decomposition (precipitation) and fusion processes are widely used techniques in ZnSt2 production. The product purity has been a major concern in most of the ZnSt2 applications such as PVC stabilization, coating of textile goods, additive in cosmetic products. In this study, the production of ZnSt2 using precipitation, fusion and modified fusion processes was investigated based on product purity. Raw materials and ZnSt2 were characterized by using various techniques.In the precipitation process, in order to maximize the solubility of sodium stearate and to minimize the water evaporation, the reaction was carried out at 70°C. 2.5% (w) NaSt was used in the reaction at this temperature. The equivalent, excess Zn and deficient Zn cases were studied to determine the raw materials ratio on product purity. Equivalent raw materials produced highest product purity. From washing experiment, it was seen that Na2SO4 adsorption did not take place on to wet ZnSt2. The washing water to zinc stearate ratio was found to be 40 dm3/kg for effective removal of by products and raw materials unreacted at room temperature. Any further increase in the amount of water did not bring any significant removal results. In the drying of wet ZnSt2 at 100°C, it was determined that it has 85% (w) water. In IR spectra, characteristic ZnSt2 peak was observed at 1540 cm-1. ZnSt2 obtained by this process did not contain any free Na+ and SO4-2 ions as indicated by ICP, EDX and elemental analysis results. Only two of the characteristic peaks of ZnSt2 at 2. values of 6.40 and 19.58 were obtained in XRD pattern of the dried product due to low crystallinity. From SEM micrographs, it was seen that zinc stearate has lamellar structure and particle size changes between 2-4 .m. Melting point of the zinc stearate was found to be about 122°C using optic microscopy with temperature controlled hot stage.In fusion process, reaction was carried out at 140°C in equivalent amounts for different stirring rates 400, 600 and 750 rpm. The increase in mixing rate decreased the delay time occurring at the beginning of the reaction. The conversion was found to be 80% using the developed method from IR spectra. In the comparison of the experimental conversion data with shrinking core model no relation was established. In IR spectra, two peaks observed at 1540 cm-1 and 1700 cm-1 which belong to ZnSt2 COO- stretching and stearic acid C.O stretching vibrations, respectively. All of the characteristic 2. values of zinc stearate were observed for product, which means that the crystallinity of the product is high. From SEM micrographs, it was seen that zinc stearate structure is in the form of layered lamella and particle size change between 4-6 .m. The melting point of zinc stearate samples from fusion process was found to be slightly lower than 122°C by optic microscopy with temperature-controlled hotstage.In the modified fusion process, reaction was carried out at 80°C for 1 h. with equivalent amounts of stearic acid and zinc oxide in the presence of H2O. Sodium stearate 1.5% (w) was added into reaction mixture as a surfactant and its effect was examined. At the end of reaction it was seen from IR spectra that it does not significantly increase the reactants dispersion. The presence of unreacted raw materials was determined in IR spectras and XRD patterns. This result was confirmed by SEM micrographs too. In TGA analysis, thermal decomposition temperature of zinc stearate was found to be 250°C. The use of zinc stearate in n-paraffin wax shifted the thermal decomposition temperature of wax 10°C. Increasing the amount of zinc stearate in n-paraffin increased the decomposition temperature of wax.According to the results of this study, for pure zinc stearate production precipitation process should be preferred in spite of high wash water consumption. The fusion and modified fusion processes needs to be studied further to increase the conversion and decrease the delay time.Master Thesis The Development of Synergistic Heat Stabilizers for Pvc From Zinc Borate-Zinc Phosphate(Izmir Institute of Technology, 2004) Erdoğdu, Cem Aykut; Balköse, DevrimPoly(vinyl chloride) (PVC), releases smoke and toxic gases (hydrogen chloride, HCl) during heating at temperatures above 140 C with the result of dehydrochlorination reaction. Obtaining flame retardant and smoke suppressed PVC compositions are getting more and more important. PVC is widely applied as a covering insulation for electrical and communication cables and in domestic uses such as window frames, doors, profiles, sidings and gutters because of its high level of combustion resistance.For this reason, many additives are studied to achieve better compositions than the present ones.In this study, the synergistic effects of zinc borate (ZB) . zinc phosphate (ZP) on thermal stability of plastigels obtained from PVC and dioctylphthalate (DOP) plastisols were investigated using spectroscopic and thermal techniques. Plastigels having a total of 2.5 parts (w/w) of zinc borate and zinc phosphate, 80 parts (w/w) of DOP and 100 parts (w/w) of PVC were gelled at 140 C for 15 minutes in a vacuum oven. The plastigel films having different compositions of ZB and ZP were investigated after heating at 140°C and 160 C from 15 minutes to 90 minutes by using Fourier Transform Infrared (FT-IR) spectroscopy, Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX). The kinetic studies were made by PVC Thermomat 763 instrument. HCl gas released due to heating of the plastigel films at both 140 C and 160°C in PVC Thermomat instrument under nitrogen gas increases the conductivity of deionized water in measuring vessels of this instrument. By measuring the conductivity change in water caused by the absorption of HCl released, the thermal degradation of PVC plastigel films were studied by means of reaction rates, rate constants and activation energies. Compositions having only ZB or ZP have retarded dehydrochlorination of PVC compared with the control sample. However, the compositions with both ZB and ZP have a superior synergistic effect on char formation of PVC. Since induction times of the compositions having both ZB and ZP were higher than that of the control samples having only ZB or only ZP, the synergistic effect was observed.The compositions greatly promote the char formation of PVC. The thermal stability of plastigels was also studied by their yellowness index (YI). The elemental compositions of these films were investigated in atomic scale using EDX and SEM and their compositions were calculated both for particles and matrix.Master Thesis Preparation and Characterization of Metal Soap Nanofilms(Izmir Institute of Technology, 2005) Öztürk, Serdar; Balköse, Devrim; Balköse, DevrimIn this study, the production of metal (zinc and calcium) stearate nanofilms by Langmuir-Blodgett (LB) film deposition process and their structural and electrical characterizations were investigated. The interaction of stearic acid monolayer with calcium, zinc cations as functions of pH, temperature, concentration of metal cation in the subphase and barrier speed was examined in detail. The effects of transfer surface pressure, the dipping speed, drying period, pH, concentration of metal cations in the subphase and temperature in the deposition of metal stearates onto glass substrates were optimized. Metal stearate LB films were prepared and characterized by X Ray Diffraction technique. It was revealed that the zinc stearate arrangement may be identified as under the orthorhombic (R) subcell with chain tilt angle of 31o, which was confirmed by IRspectrum of zinc stearate. Atomic Force Microscopy and Scanning Electron Microscopy images showed that surface roughness on glass substrates was decreased by firstly chrome coating and then silver coating. Zinc stearate coated surfaces have large crystal size around 90 nm in agreement with XRD calculation and contained grains and defects.The results of LB film deposition processes, structural characterization of LB films and the water vapour adsorption experiments presented that ZnSt2 LB films were easily formed and have good ordered structure in comparison to CaSt2 LB films. Therefore ZnSt2 LB films were chosen to study humidity sensor characteristics. Conductivity of ZnSt2 LB films was easily affected from environmentalconditions. No hysteresis during adsorption and desorption of water vapor on conductivity-voltage measurements was observed for zinc stearate LB film.As a result, zinc stearate LB films can be used as humidity sensor. By measuring conductivity in an humid atmosphere, humidity could be determined.Master Thesis Water vapour permeable edible membranes(Izmir Institute of Technology, 2005) Alyanak, Didem; Balköse, DevrimIn this study, polysaccharide based edible films were prepared and characterized. Also water vapour sorption, diffusion and permeability characteristics of these films were studied. For these purposes cellulose ethers such as sodium salt of carboxymethyl cellulose (NaCMC) and hydroxypropylcellulose (HPC) were used as a film forming materials. Distilled water and glycerin were used as solvent and plasticizer respectively. To determine the effect of polymer concentration of the film forming solution on the film properties, NaCMC and HPC films were prepared from three different concentrations (3, 4, 5g polymer/100ml distilled water) of film forming solutions. During the characterization studies of the films, to determine the elements and structural composition of the films, energy dispersive X-Ray and scanning electron microscopy analyze were applied to NaCMC and HPC based edible films. Also, X-Ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry analysis were applied to determine the form of elements, functional groups and glass transition temperature.Water vapour sorption capacities of NaCMC and HPC based films were measured nearly 70%w and 25%w respectively. GAB and Halsey models were found to give the best fit for the water vapour sorption data of both NaCMC and HPC films. Diffusion coefficient of water vapour in vacuum microbalance test was higher than that determined using the humidity chamber, this case could be result of the structural changes of films such as formation of porous structure in microbalance tests due to the fast drying of films by high vacuum. NaCMC based edible films showed higher diffusion coefficient values than HPC based films, due to the heterogeneous structure and bigger pore dimensions of the NaCMC films that was observed in the scanning electron micrographs. Water vapour permeability (WVP) of both films increased with increasing thickness and increasing film forming solution concentration and WVP values of NaCMC based films were higher than the WVP values of HPC films. In mechanical properties, while NaCMC films have brittle, stronger and stiffer structure, HPC films show elastic and ductile property.Master Thesis The Development of Zinc Borate Production Process(Izmir Institute of Technology, 2004) Eltepe, Hüdal Emre; Balköse, Devrim; Balköse, DevrimThe main objective of this study is the production of zinc borate which is used in large quantities as flame retardent and smoke subpressent material by making use of ourcountry.s resources which is the largest boron reserves in the world. The development of commercially acceptable zinc borate production process was investigated from several different views and the samples obtained were characterized by using different techniques. The physico-chemical properties of each sample were characterized by X-Ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, thermal gravimetric analysis (TGA). Several forms of zinc borate with various dehydration temperatures are possible to obtain.A popular form of zinc borate which dehydrates above 290 C was obtained in this study.