Studies that involve natural fiber orientation in a matrix were mostly based on regulating shear forces during mixing of fiber and matrix. This study attempts to propose a novel technique for orientating natural fibers like cellulose in a viscous polymer matrix such as polylactic acid (PLA) by applying the concepts of magnetism. Orientation of cellulose fibers in a PLA was achieved by modifying the cellulose fibers with a ferromagnetic entity and subjecting to a magnetic field. Chemically modified cellulose fibers (CLF) were oriented in dilute polylactic acid by subjecting the fiber and matrix to a magnetic field of ≈ 4T (Tesla). CLF and Microcrystalline cellulose (MCC) were oxidized with Hydrogen peroxide and further reacted with activated Ferrous sulphate heptahydrate (FeSO4.7H2O) in order to form Cellulose-Fe complexes. Chemically modified CLF was characterized by spectroscopic, thermal and morphological methods. The results from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR spectroscopy) agree that coordination bonds were formed between deprotonated and/or oxidized hydroxyl groups of cellulose and Fe2+ ions. Powder X-ray diffraction (PXRD) was used to compare the crystallinity of unmodified and modified samples of CLF. Thermal properties of modified cellulose were studied using thermogravimetric analysis (TGA) and a differential scanning calorimeter (DSC). Scanning electron microscopy (SEM) results showed that there was minimal morphological change occurred to cellulose after treatment. It was also observed that the electrical conductivity of cellulose modified with Fe 2+ was higher than that of unmodified samples. The modified CLF was then mixed with polylactic acid diluted with dichloromethane and the fibers in the matrix suspension were subjected to a magnetic field of ≈ 4T. The suspension was allowed to solvent cast inside a glass vial in the magnetic field. Morphological examination of the fiber matrix composites using confocal microscopy showed that CLF were successfully oriented along the flux direction of the magnetic field.

Studies that involve natural fiber orientation in a matrix were mostly based on regulating shear forces during mixing of fiber and matrix. This study attempts to propose a novel technique for orientating natural fibers like cellulose in a viscous polymer matrix such as polylactic acid (PLA) by applying the concepts of magnetism. Orientation of cellulose fibers in a PLA was achieved by modifying the cellulose fibers with a ferromagnetic entity and subjecting to a magnetic field. Chemically modified cellulose fibers (CLF) were oriented in dilute polylactic acid by subjecting the fiber and matrix to a magnetic field of ≈ 4T (Tesla). CLF and Microcrystalline cellulose (MCC) were oxidized with Hydrogen peroxide and further reacted with activated Ferrous sulphate heptahydrate (FeSO4.7H2O) in order to form Cellulose-Fe complexes. Chemically modified CLF was characterized by spectroscopic, thermal and morphological methods. The results from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR spectroscopy) agree that coordination bonds were formed between deprotonated and/or oxidized hydroxyl groups of cellulose and Fe2+ ions. Powder X-ray diffraction (PXRD) was used to compare the crystallinity of unmodified and modified samples of CLF. Thermal properties of modified cellulose were studied using thermogravimetric analysis (TGA) and a differential scanning calorimeter (DSC). Scanning electron microscopy (SEM) results showed that there was minimal morphological change occurred to cellulose after treatment. It was also observed that the electrical conductivity of cellulose modified with Fe 2+ was higher than that of unmodified samples. The modified CLF was then mixed with polylactic acid diluted with dichloromethane and the fibers in the matrix suspension were subjected to a magnetic field of ≈ 4T. The suspension was allowed to solvent cast inside a glass vial in the magnetic field. Morphological examination of the fiber matrix composites using confocal microscopy showed that CLF were successfully oriented along the flux direction of the magnetic field.

Biodegradable thermoplastic composites were prepared using high modulus lyocell fibers and cellulose acetate butyrate (CAB). Two reinforcement fiber types: fabric and continuous fiber tow were used. Fabric had advantages of uniform alignment and easier processing, but lacked the use as a unidirectional reinforcement and a continuous method of matrix application. Three different matrix application methods were screened for both fiber types. Matrix application by suspension of particles in water was not feasible because of particle sizes > 15 &micro m. The other disadvantages were high moisture absorption during matrix application and void formation during consolidation. Melt processing technique using alternating sandwich structure of fabrics and CAB films produced composites with impressive appearance, low void contents and low moisture absorption. However, SEM results revealed interfacial failure and extensive fiber pull out. Relatively larger fiber and matrix regions were present on the scale of 10^-3m. Solution prepregging technique using methyl ethyl ketone (MEK) as a solvent for CAB and continuous fibers as reinforcement produced composites with uniform matrix distribution, high tensile strengths and high modulus, and even wetting of fibers by CAB. A maximum tensile modulus of 21.5 GPa and a maximum strength of 251.7 MPa were achieved for a continuous fiber reinforced composites at a volume fraction of 66.5% compared to 0.8 GPa and 76 MPa for the matrix, respectively. Void contents and water absorption were relatively high compared to comparable carbon fiber composites. / Master of Science

<p>Predmet doktorske disertacije je ispitivanje mogućnosti karakterizacija novih biorazgradivih kompozitnih filmova na<br />bazi biljnih proteina. Osnovno istraživanje se bazira na<br />ispitivanju mogućnosti dobijanja kompozitnih filmova na bazi<br />obnovljivih sirovina, vlažnim postupkom (&quot;casting&quot; metoda),<br />karakterizaciji dobijenih filmova i modifikaciji uslova dobijanja<br />radi pobolj&scaron;anja osobina formiranog filma. Istraživanja se<br />zasnivaju na dobijanju filmova na bazi pogače uljane tikve<br />golice (Cucurbita pepo L. c. v. Olinka) (pumpkin oil cake &ndash;<br />PuOC), njenog proteinskog izolata i njihove kombinacije sa<br />drugim filmogenim polimerima (proteinima i polisaharidima).<br />Istraživanje podrazumeva procenu mogućnosti primene PuOC<br />radi delimične zamene op&scaron;te poznatih filmogenih materijala,<br />kao i produkciju filmova od PuOC i od proteinskog izolata<br />PuOC. Za produkciju filmova, od važnosti je ispitivanje<br />procesnih parametara (temperatura, pH, period denaturacije,<br />uslovi su&scaron;enja, itd.) i komponenti koje formiraju film (količina<br />polimera sa sposobno&scaron;ću formiranja filma, količina i vrsta<br />plastifikatora, količina i vrsta agenasa za umrežavanje, itd.). S<br />obzirom na velik broj parametara koji utiču na formiranje filma,<br />kao i na osobine formiranih filmova, ispitano je međusobno<br />delovanja vi&scaron;e faktora na mogućnost produkcije i osobine<br />dobijenog filma. Odabir i optimizacija procesnih parametara i modelovanje produkcije filmova izvedeno je implementiranjem<br />nove kompjuterske i analitičke metodologije. Osobine značajne<br />za dalju primenu dobijenih filmova podrazumevaju mehaničke<br />osobine (zateznu jačinu i izduženje pri kidanju), barijerne<br />(propustljivost gasova) i fizičko-hemijske karakteristike<br />(rastvorljivost, količinu rastvorljivih proteina, biolo&scaron;ku<br />aktivnost u vidu antioksidantne aktivnosti), a ispitane su u cilju<br />deklarisanja potencijalne aplikacije filma. Dodatno, ispitana je<br />mogućnost produkcije kompozitnih filmova proteinski<br />izolat/hitozan, kao i primena enzimskog umrežavanja (crosslinking)<br />enzimom transglutaminaza (TGaza), radi dobijanja<br />filmova sa unapređenim karakteristikama. Istraživanja su<br />vođena i u smeru karakterizacije strukture nastalih filmova,<br />primenom tehnika elektron skenirajuće mikroskopije,<br />deferencijalne skening kalorimetrije, gasne hromatografije i<br />Furije transformi&scaron;uće infracrvene spektrofotometrije.</p> / <p>The subject of the doctoral dissertation is to examine the possibility of<br />production and characterization of new biodegradable composite<br />films based on plant proteins. The research is based on an<br />examination of the possibility of obtaining composite films based on<br />renewable raw materials, using the casting method, on the<br />characterization of the obtained films and the requirement for the<br />modification to improve the properties of the formed film. The<br />research is aimed to evaluate the possibility of the production<br />the new biodegradable films based on hull-less pumpkin<br />(Cucurbita pepo L. c. v. Olinka) oil cake (pumpkin oil cake -<br />PuOC), its protein isolates and their combinations with other<br />filmogenous polymers (proteins and polysaccharides). The<br />study involves partial replacement of commonly well-known<br />filmogenous materials with PuOC, and production of films<br />based on the whole PuOC and the protein isolates from PuOC.<br />For film production, it is important to investigate the process<br />parameters (temperature, pH, denaturation period, drying conditions,<br />etc.), film-forming components (the amount of polymer with filmforming<br />ability, the amount and type of plasticizer, the amount and<br />type of cross-linking agents, etc..). As the large number of parameters<br />influence the film formation, as well as the properties of formed<br />films, the interaction of several factors which affect the possibility of<br />the production and properties of the obtained film, was examined.<br />Selection and optimization of process parameters and modeling of<br />film production will be carried out by implementing a new computer<br />and analytical methodology. Characteristics important for further<br />application of the obtained films include mechanical properties<br />(tensile strength and elongation at break), barrier (gas permeability)<br />and physical-chemical properties (solubility, the amount of soluble<br />proteins, biological activity in the form of antioxidant activity) and<br />were tested for the purpose of declaring potential application of the produced films. Additionaly, the possibility of production of composite films protein isolate/chitosan, and the application of enzymatic networks (cross-linking) by the enzyme<br />transglutaminase, in order to obtain films with improved<br />properties, was examined. Research was conducted in the<br />direction of the characterization of films formed by applying the<br />techniques of scanning electron microscopy, diferential<br />scanning calorimetry, gas chromatography and Fourier<br />transforming infrared spectrophotometry.</p>

This thesis describe methods to improve the interfacial stability of an interpenetrating phase composite (IPC) polyvinylurethanecarbonate), and to increase the hydrophobicity of the polymer phase. The current IPCs introduce covalent bonding between the phases via silanizing agents to enhance the interfacial stability. Incorporation of the silanizing agents was also intended to reduce the IPC’s sensitivity to interfacial hydration, thereby enhancing the IPC’s resistance to degradation during aging. Lysine diisocyanate was used to increase the hydrophobic character in the polyvinylurethanecarbonate resin. The polymer resins were infiltrated into porous CPP blocks with 25 volume% interconnected porosity and polymerized to produce the IPCs. After mechanical testing following a aging study it was found that the silanizing agents contributed to stability of the mechanical properties under aqueous conditions. It was concluded that the mechanical properties and stability were comparable to available biodegradable composites, as well as being biocompatible to a preosteoblast model cell line.

This thesis describe methods to improve the interfacial stability of an interpenetrating phase composite (IPC) polyvinylurethanecarbonate), and to increase the hydrophobicity of the polymer phase. The current IPCs introduce covalent bonding between the phases via silanizing agents to enhance the interfacial stability. Incorporation of the silanizing agents was also intended to reduce the IPC’s sensitivity to interfacial hydration, thereby enhancing the IPC’s resistance to degradation during aging. Lysine diisocyanate was used to increase the hydrophobic character in the polyvinylurethanecarbonate resin. The polymer resins were infiltrated into porous CPP blocks with 25 volume% interconnected porosity and polymerized to produce the IPCs. After mechanical testing following a aging study it was found that the silanizing agents contributed to stability of the mechanical properties under aqueous conditions. It was concluded that the mechanical properties and stability were comparable to available biodegradable composites, as well as being biocompatible to a preosteoblast model cell line.

Despite the recent development in PLA and PLGA based medical devices, there are still needs to further improve the mechanical performance of bioresorbable medical implants and their bioactivity. This is normally done by optimizing the filler compositions in selected groups ofbiodegradable polymer matrices. In this study, the effects of various filler levels on mechanical strength and thermal properties of PLA and PLGA composites were investigated. Composites containing different dosage of osteoconductive HAp with various particles size (0-5μm, 0-50 μm, nano size), β-TCP, bioactive glass and biodegradable Poly-L-lactide and Polylactide-glycolic acid was manufactured with melt blending, using a twin-screw extruder.The samples were investigated by Differential Scanning Calorimetry (DSC), thermo gravimetric analysis (TGA), Scanning Electron Microscopy (SEM), viscometer, three points bending machine, and Optical Microscopy (OM). The Extruder produced a porous profile. The result from TGA and SEM indicated that there was homogenous filler dispersion in the matrix after compounding.The result from DSC and Viscometer shows that there was some degradation duringcompounding. Mechanical properties of composites were modified by adding filler to matrix. The addition of Bioactive glass, as a filler, increases the degradation of the polymer matrix. The best filler that was applied is 0-5μm and nano HAp. Also in in-vitro degradation part of this thesis work, the effects of calcium phosphate materialsare investigated on degradation process.