Master Degree / Yüksek Lisans Tezleri

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

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Author: search.filters.author.Tıhmınlıoğlu, FundaSubject: search.filters.subject.Polymeric composites

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Now showing 1 - 4 of 4
  • Master Thesis
    Preparation and Characterization of Polypropylene Based Composite Films
    (Izmir Institute of Technology, 2001) Pehlivan, Hilal; Tıhmınlıoğlu, Funda
    In the scope of this study, preparation of silver . natural zeolite reinforced polypropylene (PP) composite system possessing antibacterial properties via ion exchange process and characterization by means of different techniques (FTIR, TGA, DSC, mechanical tests, optical microscopy) were aimed. It has been established that zeolites are suitable for removing Ag ions from silver containing solutions and that silver zeolites are increasingly investigated as germicidal, bactericidal, antifungal, and antiseptic components in different compositions (Hagiwara 1990, Kawahara 2000, Klasen 2000).In the present study, prior to the ion exchange studies, water sorption behavior of PP . clinoptilolite rich natural zeolite composites was investigated, since the ion exchange process was to be conducted in aqueous media. It was observed that a hydrophobic polymer, PP attained the property of water sorption due to the porous structure of the composite films. The effective diffusivity of liquid water in the PP-zeolite composites prepared by hot press and extrusion techniques varied in the range of 0.3- 9.9 x10-10 and 0.1 - 3.3 x10-12 cm2/s, respectively. Silver loading to PP - zeolite composites was provided by means of two different methods. In Method I, PP - zeolite composite films were treated with a variety of silver ion containing solutions (5 to 50 ppm AgNO3 solution), whereas in Method II silver exchanged zeolite minerals (prepared with initial AgNO3 concentrations of 50, 500, and 5000 ppm) were molded with PP in the presence of DOP (Dioctyl Phthalate). The amounts of Ag+ loaded per gram of zeolite for initial AgNO3 concentrations of 50, 500, and 5000 ppm were determined as 4.36, 27.85, and 183.78 mg, respectively. Antibacterial activity tests against E.coli indicated that the samples obtained in Method II were superior to those prepared by Method I since the penetration of silver ions to the zeolite phase was limited by the PP phase in the case of Method I. However, the discoloring effect of silver ion was readily observed for the samples prepared by Method II as indicated by the discoloration parameters. The release of Ag+ to water was found to be negligible as reported in literature leading to long . term antibacterial activity.The thermal characterization studies showed that the addition of the zeolite increased the crystallinity of the structure acting as a nucleating agent in PP crystallization as well as retarded the degradation temperature of PP. At low silver concentrations, the zeolite behaved as a decelerating agent in PP, however at higher silver concentrations, the composites degraded at a faster rate than pure PP. Yet the activation energy values for the thermal decomposition reactions of Method II was considerably lower indicating that the decomposition has been accelerated by the presence of silver.It was found that the addition of the zeolite into the PP matrix decreased the density of pure PP (0.89 g/cm3) due to the formation of voids. However, a systematic approach was not observed with the increasing zeolite content as a consequence of the uneven zeolite distribution. On the other hand, a considerable enhancement was noticed for the tensile tested film densities changing between 0.58 - 0.78 g/cm3, which are in a better agreement with the commercially desired range (0.6 - 0.65 g/cm3) for packaging applications of PP composites. Mechanical tests indicated that the addition of the zeolite tended to decrease the yield stress values while a slight decrease was observed for Young moduli. The effect of silver on the Young Modulus values of the composites is not quite significant, however the yield stress values increased from 23.6 to 29.5 MPa with the increasing silver concentration.Consequently, of all the composite films prepared by Method II, the ones loaded with 4.36 (mg Ag+/g zeolite) containing 2, and 4 % wt zeolite were selected to be the most appropriate, considering the thermal, mechanical, and structural characteristics as well as the discoloring actions.
  • Master Thesis
    Preparation and Characterization of Hydroxyopatite and Polymer Composite Biomaterials
    (Izmir Institute of Technology, 2002) Gültekin, Naz; Tıhmınlıoğlu, Funda
    In the thesis, the preparation and characterization of polylactide-Hydroxyapatite(HA) composite films for biomaterial applications have been studied. The effects of number of parameters such as polymer type, HA loading, surface modification and its concentration on the mechanical, thermal microstructural and hydrolytic degradation properties of the composites were investigated. Four different types of polymers, Poly (L-lactide)(PLA1), 96/4 L-lactide,D-Lactide Copolymer (PDLA1), Poly (L-Lactide)(PLA2), and 67/23 Poly (L-Lactide-co-D,L-Lactide)(PDLA2), have been used. In this study, PolyLactide-HA composite films have been prepared by solvent-casting technique. The HA powder was synthesized by precipitation technique. Interfacial interactions between HA and polylactide polymer were modified to improve filler compatibility and mechanical properties of the composites by surface treatment of the HA with two different silane coupling agents; 3-aminopropyltriethoxysilane (AMPTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) at three different concentration. Silane treatment indicated better dispersion of HA particles in the polymer matrix and improvements in the mechanical properties of the composites compared to the untreated HA loaded polylactide composites. Tensile test results showed that the maximum improvement in the mechanical properties of the composites was obtained for the PLA composites containing 1 wt % aminofunctional silane treated HA and 0.5 wt % mercaptopropyltrimethoxy silane treated HA for PDLA composites. Scanning electron microscopy studies also revealed better dispersion of silane treated HA particles in the polymer matrix. Thermal degradation kinetics of the composites was investigated and it was found that addition of HA into polymer matrix decreased the thermal degradation temperature and also slowed down the degradation rate. In this study, the hydrolytic degradation of poly (L-Lactide)(PLA), poly (L-Lactide-co-D-Lactide) (PDLA) and their hydroxyapatite (HA) loaded composites (10-50-w/w %) were investigated in simulated body fluid (SBF) at 37 0C and at pH 7.4 by in vitro static testing. Using different techniques, namely weighting to quantify water absorption monitored the hydrolytic degradation and weight loss, scanning electron microscopy (SEM) to observe morphological changes occurred at the surface of the films over time. At the end of the 150 days, only 12.5 wt % and 9.5 wt % of weight PLA1 and PLA2 were lost respectively. Degradation of the copolymers was faster than PLA1 and PLA2 and weight loss data of PDLA1 and PDLA2 were found to be nearly same with 17.5 wt % and 17 wt %, respectively. The changes of pH on all polymer were stable at 7.4, because of simulated body fluid indicates buffer solution properties. Degradation rate of PLA and PDLA composites containing 10 wt % HA decreased, and also water absorption of these samples increased. Weight loss decreased approximately from 12 wt % to 5 wt % and water absorption increased from 10 wt % to 13 wt % for PLA composites containing 10 wt % HA. The change of microstructural properties of obtained composites has been determined in simulated body fluid as a function of time. It was found that the surface of polymer composite films was coated with the calcium phosphate layer. This coating was increased with HA loading and ageing time.
  • Master Thesis
    Preparation and Characterization of Polypropylene Cellulose Composites
    (Izmir Institute of Technology, 2004) Atikler, Ulaş; Tıhmınlıoğlu, Funda
    In recent years, much effort has been driven to replace glass fibers, which were used to reinforce thermoplastic composites, with natural fibers. In this study, three natural fibers, namely cellulose (CE), sawdust (SD) and wheat straw (WS) were employed as reinforcement to polypropylene (PP) polymer matrix. The most important problem encountered with natural fiber/PP composites is the inherent incompatibility between hydrophilic natural fibers and hydrophobic PP matrix, thus coupling agents were employed to alter incompatibility between fiber and matrix. Coupling agents enhance interfacial interactions by chemical and physical bonding between fiber and matrix. Surface treatment of natural fibers were carried out with two kinds of silanes;(3-aminopropyl)-triethoxysilane (AS) and methacriloxy propyl trimethoxy silane (MS), and maleic anhydride grafted polypropylene (MAPP). Silane coupling agents were agitated in aqueous ethanol solution in the presence of fibers at weight percents of 0.5, 1 and 2.5 with respect to fiber weight. MAPP was compounded during melt mixing of fiber and PP at weight percents of 2.5, 5 and 10 with respect to PP weight PP/fiber composites were prepared in a rheomixer equipped with two rotor blades and adjustable temperature, mixing rate and mixing time. Composites were prepared at 185 oC, 50 rpm mixing rate and 10 minutes mixing time. Torque values of each composite formulation were recorded with respect to time to determine changes in rheological properties of composites. It was found that increase in fiber loading increases stabilization torque of composites. Mechanical properties of PP/fiber composites were significantly enhanced byemployment of coupling agents and MAPP was found to be the most effective coupling agent. Mechanical properties of SD composites were found to exhibit the best performance compared to C and WS. Extent of interfacial interactions were evaluated with Pukanszky and Nielsen model and superior performance of MAPP in enhancing interfacial interactions was confirmed by these two models. Optimum conditions for coupling agents were found to be 1 wt % for silane coupling agents and 5 wt % for MAPP. It was found that water sorption and void fraction of the composites decreased with employment of coupling agents. Among the coupling agents, MAPP exhibited the best performance in decreasing water sorption and void fraction of composites confirming results of mechanical tests. Scanning electron micrographs (SEM) used to illustrate the effect of coupling agents on adhesion between fiber and matrix and fracture modes of the composites. In addition, FTIR analysis revealed the decrease in hydrophilicity of fibers with silane treatment and new bond formations with employment of MAPP.
  • Master Thesis
    Interfacial Enhancement of Polypropylene-Zeolite Composites
    (Izmir Institute of Technology, 2002) Metin, Dildare; Tıhmınlıoğlu, Funda
    The objective of this study was to improve the properties of polypropylene-zeolite composites by enhancement of the interphase between polypropylene and zeolite. Surface treatment of zeolite was applied for modification of interfacial interactions between zeolite and polypropylene. Surface treatment of natural zeolite was carried out with (3 wt%) polyethyleneglycol (PEG) and three different silane coupling agents namely, 3-aminopropyltriethoxysilane (AMPTES), methyltriethoxysilane (MTES), and 3-mercaptopropyltrimethoxysilane (MPTMS) at four different concentrations (0.5, 1, 1.5 and 2 wt%) to find suitable surface modifier for improving filler compatibility and mechanical properties. PP composites containing (2, 4 and 6 wt%) untreated or treated zeolite and plasticizers: dioctylphthalate (DOP) or epoxidized soybean oil (EPS) were prepared by extrusion technique. The effects of the modifications and zeolite content on the thermal, mechanical, structural and physical properties of PP composite were investigated. The contact angle measurements and FTIR analyses of untreated and silane treated zeolite samples and water sorption results of PP-zeolite composites showed that hydrophobicity of zeolite significantly increases with surface modification. Thermal analyses indicated that the addition of zeolite and silane treatment to the PP-EPS matrix did not change the melting and degradation temperature of the composites. However, these modifications were found to increase the crystallinity and crystallization temperature of the composites due to the nucleating effect of the zeolite. The mechanical properties of PP composites containing silane treated zeolite indicated significant improvements compared to the composites containing untreated filler. The most enhanced dry and wet mechanical properties were observed for PP composites containing 1 wt% AMPTES treated zeolite. The effect of interfacial interactions and adhesion between zeolite and PP was evaluated by various semiemprical equations: Pukanszky model, Nicholais and Narkis model and Nielsen model. The improvement in adhesion between silane treated zeolite and PP was also confirmed from these models. Moreover, the water sorption and mechanical test results, as well as scanning electron micrographs and optical micrographs of the composites verify that silane coupling agents enhanced compatibility and interfacial adhesion between zeolite particles and PP matrix strongly led to an improvement of the mechanical properties of the composites. Consequently, 1 wt% AMPTES was proposed to be the most appropriate surface modifier by considering the water sorption results, thermal, mechanical and microstructure analyses of PP-zeolite composites.