Master Degree / Yüksek Lisans Tezleri
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Master Thesis Tribological Behaviour of Polymer Nanocomposities Containing Tungsten Based Nanoparticles(Izmir Institute of Technology, 2007) Karal, Kazım; Tanoğlu, MetinThe 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 Preparation and Physical Characterization of Clay/Epdm Nanocomposites(Izmir Institute of Technology, 2008) Karşal, Çiçek; Tanoğlu, MetinPolymer/clay nanocomposites have been extensively studied in recent years because they often exhibit improved properties different from their micro and macrocomposite counterparts. Addition of organophilic layered silicates to the polymer produces effective polymer nanocomposites by intercalation of macromolecules into the interlayer spaces. The performance of polymer/clay composites is not only related to the nature of the clay but also to the reinforcing mechanism of filler and the preparation conditions.In this study, the effects of mixing conditions and effect of aging on mechanical,physical and thermal properties of ethylene-propylene-diene rubber (EPDM)/Organo modified montmorillonite (OMMT) nanocomposites were studied at two different clay loadings 5 wt.% and 10 wt.%. EPDM/OMMT nanocomposites were prepared by melt blending method. The experimental results of X-ray diffraction (XRD) and scanning electron microscopy showed that the organically modified MMT existed in the form of an intercalated structure and that was exfoliated in EPDM matrix depending on the mixing conditions. XRD patterns showed that the interlayer distance of the organically modified clay was 30.9A, which was larger than those of the unmodified clay (14.6A).The mechanical evaluation of the nanocomposites was performed by tensile and tear testing. The mechanical tests showed that the properties of nanocomposites were significantly improved with addition of OMMT. The effects of the processing conditions were manifested in both the morphology and mechanical properties, which showed significant increase when optimized process conditions are applied. In addition, chemical test was performed on the nanocomposites to monitor the degradation of the mechanical properties. It was found that the reduction of the mechanical properties of nanocomposites after aging process is lower as compared to those of neat EPDM.Master Thesis Preparation and Characterization of Polypropylene Based Composite Films(Izmir Institute of Technology, 2001) Pehlivan, Hilal; Tıhmınlıoğlu, FundaIn 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, FundaIn 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 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 Mechanical and Thermal Properties of Non-Crimp Glass Fiber Reinforced Composites With Silicate Nanoparticule Modified Epoxy Matrix(Izmir Institute of Technology, 2006) Bozkurt, Emrah; Tanoğlu, MetinIn the present study, epoxy based nanocomposites were prepared with modified and unmodified silicate nanoparticules to apply as a matrix resin for non-crimp glass fiber reinforced polymer composites. The effects of the silicate nanoparticules on the mechanical, thermal and flame retardancy properties of glass reinforced composites were investigated. Laminates were manufactured with hand lay-up technique and cured under compression. To intercalate the layers and obtain better dispersion of silicate layers within the matrix, silicate (montmorillonite, MMT) particules were treated with hexadecyltrimethylammonium chloride (HTAC) surfactants. X-ray diffraction of silicates with and without surface treatment indicated that intergallery spacing of layered silicate increased with surface treatment. Tensile tests showed that silicate loading had minor effect on the tensile strength and modulus of the composite laminates. Flexural properties of laminates were improved with the addition of silicate due to the improved interface between glass fibers and epoxy matrix. With the addition of modified MMT (OMMT), interlaminar shear strength (ILSS) of laminates decreased slightly but fracture toughness (KIC) of laminates were increased. The fracture surfaces were examined with scanning electron microscopy (SEM) and the results revealed that fracture mechanisms were altered due to the presence of silicates in the matrix. Differential scanning calorimetry (DSC) results showed that modified silicate particules increase the glass transition temperatures (Tg) of composite laminates. Incorporation of OMMT particules increased the dynamic mechanical properties of non-crimp glass fiber reinforced epoxy composites. It was found that the flame resistance of composites was improved due to silicate particule additions into the epoxy matrix.Master Thesis Processing and Characterization of Polymer Based Composites With Superior Impact Resistance(Izmir Institute of Technology, 2003) Seyhan, Abdullah Tuğrul; Tanoğlu, MetinFiber reinforced polymeric composite materials have recently gained widespread use in military, transportation, energy and civil engineering applications. Resin Transfer Molding (RTM) and Vacuum Assisted Resin Transfer Molding (VARTM) process have become important in the manufacture of these types of composites. In those techniques, use of fiber preforms offer some distinct advantages. Using thermoplastic binders that bond the fabrics together allows the plies to be consolidated into near net shape preform.In the present work, glass preforms were consolidated by application of heat and pressure over plies of the glass fabrics that were coated with various concentration of thermoplastic polyester binder. Composite laminates with and without binder were fabricated by utilizing VARTM technique. The peel strength of the preforms with various binder contents was measured to determine the optimum binder concentration. The highest peel strength was obtained from preforms that were prepared with about 9 wt.% of the binder. Preform compression test was also performed using universal test machine with preforms composed of eight plies of glass fabrics with binder (3,6 and 9 wt.%) and without binder. It was observed that the binder has significant effect on the degree of preform compaction. The highest thickness reduction and therefore fiber volume fraction of the preforms was reached via 3 wt.% of binder. The flexural strength and modulus, compressive strength and modulus through ply-lay up and in-plane loading directions, apparent interlaminar shear strength, mode I interlaminar fracture toughness of the composites with and without binder were measured to evaluate the effects of the binder on the mechanical properties of the composite plates. It was found that the flexural strength, mode I interlaminar fracture toughness of the E-glass/polyester composite system decreases 30 and 40 percentage, respectively due to the presence of 3 wt.% and 6 wt.% of binder. On the other hand, the flexural modulus of the composite increases while the apparent interlaminar shear strength remains almost constant by the introduction of the binder. The ply-lay up compressive strength and modulus were found to increase up to 3 wt.% of binder and decrease upon further addition of binder. The same findings are valid for the compressive strength and modulus through in-plane loading direction. Ballistic test was performed on E-glass/polyester composite panels according to NATO standards 2920 using 1.1-gr. fragment-simulating projectiles (FSPs) to evaluate the effects of the binder on the ballistic performance of the E-glass/polyester composite laminates. The ultrasonic C-scan test method was used to monitor the extent of the damage on the panels due to ballistic impact. It was seen that the damage on the ballistically impacted composite panels decreases with increasing binder. A model matrix material was prepared adding various concentrations of the binder to the reacting resin system in order to follow the extend of binder dissolution within the matrix resin. It was found that there is no complete dissolution of the binder in the matrix resin.Master Thesis Preparation and Characterization of Polypropylene Cellulose Composites(Izmir Institute of Technology, 2004) Atikler, Ulaş; Tıhmınlıoğlu, FundaIn 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 Layered Silicate / Polypropylene Nanocomposites(Izmir Institute of Technology, 2006) Işık, Kıvanç; Tanoğlu, MetinLayered silicate nanocomposites are new generation materials that have unique properties obtained by low particulate loadings. In this study, layered silicate/polypropylene nanocomposites were prepared by melt intercalation method.Homopolymer PP alone and maleic anhydride-grafted polypropylene (PPgMA) as a compatibilizer were used as the matrix. Clay (Na+ montmorillonite, MMT) particles were used with and without structural modification to obtain silicate nano-layers within the PP matrix. Structural modification of MMT using hexadecyltrimethyl ammonium chloride (HTAC) was applied to obtain organophilic silicates (OMMT). XRD results demonstrated that the dispersion of the modified silicate layers and compatibilized with PPgMA (OMMT/PPgMA) is better than those for incompatibilized compositions. The addition of silicate layers increased the crystallization temperature of PP as well as the thermal stability, but the melting temperature of the nanocomposites was decreased by the addition of silicate as compared with neat PP. The mechanical characterizations exhibited an increase of 62% on tensile modulus and 15% on tensile stress at break as compared to neat PP due to the improved dispersion of silicate layers within PP in 3 wt.% OMMT/PPgMA/PP nanocomposites. The effect of clay modification and PPgMA compatibilization on the light transmission of PP nanocomposites was characterized by optical transmission analysis. For the OMMT/PPgMA/PP nanocomposites, light transmission was improved as the dispersion was enhanced. The flammability results demonstrated that unmodified MMT and modified OMMT decreased the burning rate of PP nanocomposites. The organic modification of clay and compatibilization decreased the rate of flammability. A decrease of 26% on the burning rate of PP was recorded in 10%wt. OMMT/PPgMA/PP nanocomposites.Master Thesis Interfacial Enhancement of Polypropylene-Zeolite Composites(Izmir Institute of Technology, 2002) Metin, Dildare; Tıhmınlıoğlu, FundaThe 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.