Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 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.