No description available.

Nanoparticles reinforced polymer composite films have been widely studied for their enhanced mechanical, electrical and thermal properties compared with host polymer matrix. However, most research was conducted on incorporation of nanoparticles in polymer films to improve single property and there is a lack of research on the multifunctional polymer nanocomposite films. In this work, a scalable and continuous spray deposition process was developed for the production of nanoparticles reinforced multifunctional thermoplastic nanocomposite films. This process is capable of making a thin sheet of thermoplastic nanocomposites with high nanoparticle loadings. The smallest thickness can be 40um. The objective of this study is to design and optimize the thermoplastic nanocomposite films by utilizing nanoclay and helical carbon nanotube for multifunctional application: a) high electrical conductivity and thermal stability. Helical carbon nanotube paper based thermoplastic polyurethane nanocomposite films have been studied. The electrical conductivity and thermal stability of nanocomposite films increase a lot due to the incorporation of helical carbon nanotube paper with high electrical and thermal conductivity. The peculiar helical configuration of carbon nanotubes could greatly improve the interfacial bonding between carbon nanotubes and polymer matrix. b)High wear resistance and thermal stability. A nanoclay reinforced thermoplastic polyurethane nanocomposite coating was applied on the surface of leather. Due to the high hardness and thermal stability of nanoclay, the leather coated with nanocomposite film showed an improvement of wear resistance and thermal stability.

No description available.

An environmentally benign process, which uses supercritical carbon dioxide (sc-CO₂) as a processing aid, was developed in this work to help exfoliate and disperse nanoclay into the polymer matrices at high clay content. The process involves the use of a pressurized CO₂ chamber to assist in the exfoliation and delivery of the clay into a stream of polypropylene (PP) melt within the extruder. This CO₂ method was evaluated and compared to other conventional processing techniques. It was observed that the conventional direct-melt compounding methods, with and without the direct injection of CO₂, did not show much improvement in the mechanical properties due to their inability to adequately exfoliate the nanoparticles into the polymer matrix. The commercial RTP sample prepared using a TSE and a MA compatibilizer showed moderate improvements in the clay dispersion and properties due to high shear forces and mixing capabilities of TSE. The most improvements were seen from the technique of using the pressurized CO₂ chamber, which directly injected pre-mixed sc-CO₂ and nanoclay into the polypropylene melt during extrusion. It was observed that the mechanical properties of the PP nanocomposites prepared using the CO₂ chamber technique, especially when combined with maleic anhydride (MA) compatibilizer, outperformed those of the commercial RTP samples and those of samples prepared using conventional melt compounding techniques. WAXD and TEM data showed a good degree of exfoliation for clay concentrations as high as 6.8 wt% when the clay was expanded and mixed with CO₂. At this concentration, mechanical properties such as yield strength and modulus increased by as much as 13% and 69%, respectively, relative to the pure PP, and approximately 15% higher than those of samples prepared by direct melt compounding (without the use of CO₂). Furthermore, yield-like behavior in the viscosity and a plateau in the low-frequency behavior of storage modulus, Gâ , was also attributed to polymer-clay interaction due to strong hydrogen bonding between MA groups and the hydroxyl groups on the clay surface, not just solely to the formation of percolation network due to exfoliation between clay platelets that is commonly reported in literature for clay-filled functionalized polypropylene. / Ph. D.

Polymeric fibres influence our everyday life in numerous aspects; the area of applications ranges from industrial to everyday commodities, textile and non-textile. As the global demand for the polymeric fibres increases rapidly, new innovative classes of fibres and the manufacturing processes are sought after. This thesis develops an approach to produce fine cell structure and low void fraction foams, which is then used in the manufacturing of lightweight, biodegradable foam fibres. Poly (lactic) acid-clay nanocomposite have been foamed with nitrogen and drawn to different melt draw ratio to produce foam fibres. The foam fibres are then characterized for crystallinity, Young’s modulus and the yield stress. While the drawability of foam has been demonstrated, the crystallinity as well as the mechanical properties of the foam fibres are not drastically enhanced by drawing, as would be expected. Further drawing processes of the as-spun foam fibres are recommended.

Polymeric fibres influence our everyday life in numerous aspects; the area of applications ranges from industrial to everyday commodities, textile and non-textile. As the global demand for the polymeric fibres increases rapidly, new innovative classes of fibres and the manufacturing processes are sought after. This thesis develops an approach to produce fine cell structure and low void fraction foams, which is then used in the manufacturing of lightweight, biodegradable foam fibres. Poly (lactic) acid-clay nanocomposite have been foamed with nitrogen and drawn to different melt draw ratio to produce foam fibres. The foam fibres are then characterized for crystallinity, Young’s modulus and the yield stress. While the drawability of foam has been demonstrated, the crystallinity as well as the mechanical properties of the foam fibres are not drastically enhanced by drawing, as would be expected. Further drawing processes of the as-spun foam fibres are recommended.

Research into the processing conditions and parameters of polymeric nanocomposites has always been challenging to scientists and engineers alike. Many have developed tools and procedures to allow materials to be exploited and their properties improved with the addition of nanofillers to achieve the desired end material for various applications. Initial trials are mostly conducted using conventional small scale experiments using specialised equipment within the laboratory that can replicate the larger industrial equipment. This is a logical approach as it could save time and costs as many nanocomposites are relatively expensive to produce. Experiments have previously been done using the likes of the Haake twin screw extruder to manufacture nanocomposites within the laboratory but this research project has used a novel minimixer specifically developed to replicate mixing like large twin screw extrusion machines. The minimixer uses a twin paddle system for high shear mixing in conjunction with a single screw thus theoretically allowing an infinitely long recirculation. It is this ability to mix intensely whilst allowing for as long as desired recirculation which enables the replication in this very small mixer (10-30g capacity) of the mixing conditions in a large twin screw extruder. An added feature of the minimixer is that it can undertake inline data analysis in real time. The main experiments were conducted using a comprehensive DOE approach with several different factors being used including the temperature, screw speed, residence time, clay and compatibiliser loading and two polymer MFI's. The materials used included PP, Cloisite 20A, Polybond 3200, PET, Somasif MTE, Polyurethane 80A and Single / Multi-walled Carbon nanotubes. Detailed experimental results highlighted that rheological analysis of the nanocomposite materials as an initial testing tool were accurate in determining the Elastic and Loss modulus values together with the Creep and Recovery, Viscosity and Phase Angle properties in the molten state. This approach was also used in an additional set of experiments whereby the temperature, speed, residence time and compatibiliser were kept constant but the clay loading was increased in 1% wt. increments. These results showed that the G' & G'' values increased with clay loading. Another important finding was the bi-axial stretching step introduced after the processing stage of the nanocomposite materials which highlighted a further improvement in the modulus values using rheological testing. Other tests included using inline monitoring to look into both the viscosity and ultrasound measurements in real time of the molten polymer nanocomposite through a slit die attachment to the minimixer.

Whey is a byproduct of cheese making; whey proteins are globular proteins which can be modified and polymerized to add functional benefits, these benefits can be both nutritional and structural in foods. Modified proteins can be used in non-foods, being of particular interest in polymer films and coatings. Food packaging materials, including plastics, can linings, interior coatings of paper containers, and beverage cap sealing materials, are generally made of synthetic petroleum based compounds. These synthetic materials may pose a potential human health risk due to presence of certain chemicals such as Bisphenol A (BPA). They also add to environmental pollution, being difficult to degrade. Protein-based materials do not have the same issues as synthetics and so can be used as alternatives in many packaging types. As proteins are generally hydrophilic they must be modified structurally and their performance enhanced by the addition of waterproofing agents. Polymerization of whey proteins results in a network, adding both strength and flexibility. The most interesting of the food-safe waterproofing agents are the (large aspect ratio) nanoclays. Nanoclays are relatively inexpensive, widely available and have low environmental impact. The clay surface can be modified to make it organophilic and so compatible with organic polymers. The objective of this study is the use of polymerized whey protein (PWP), with reinforcing nanoclays, to produce flexible surface coatings which limit the transfer of contents while maintaining food safety. Four smectite and kaolin type clays, one treated and three natural were assessed for strengthening qualities and the potential waterproofing and plasticizing benefits of other additives were also analyzed. The nutritional benefits of whey proteins can also be used to enhance the protein content of various foodstuffs. Drinkable yogurt is a popular beverage in the US and other countries and is considered a functional food, especially when produced with probiotic bacteria. Carbonation was applied to a drinkable yogurt to enhance its benefits. This process helps reduce the oxygen levels in the foodstuff thus potentially being advantageous to the microaerophilic probiotic bacteria while simultaneously producing a product, somewhat similar to kefir, which has the potential to fill a niche in the functional foods market. Yogurt was combined with a syrup to reduce its viscosity, making it drinkable, and also to allow infusion of CO2. This dilution reduced the protein content of the drink and so whey protein concentrate was added to increase levels in the final product. High-methoxyl pectins were used to provide stability by reducing the tendency of the proteins to sediment out. The objectives of this study were to develop a manufacturing technology for drinkable carbonated symbiotic yogurts, and to evaluate their physicochemical properties. Two flavors of yogurt drink, pomegranate and vanilla, were formulated containing inulin as prebiotic, along with probiotic bacteria, producing symbiotic dairy beverages.

In the first part of this dissertation, glass fiber reinforced/unreinforced polyamide 6 (PA6) and polyamide 66 (PA66) were compounded with three different flame retardants, which were melamine cyanurate, red phosphorus and brominated epoxy with antimony trioxide, by using an industrial scale twin screw extruder. Then, to investigate flame retardancy of these specimens, UL-94, Limiting Oxygen Index (LOI) and Mass Loss Cone Calorimeter (MLC) tests were carried out. In addition to flammability tests, thermogravimetric analysis (TGA) and tensile testing were performed. Results of the tensile tests were evaluated by relating them with fiber length distributions and fracture surface morphologies under scanning electron microscope (SEM). Incorporation of melamine cyanurate (MCA) to PA6 led to some increase in LOI value and minor reductions in Peak Heat Release Rate (PHRR) value. However, it failed to improve UL-94 rating. Moreover, poor compatibility of MCA with PA6 matrix caused significant reductions in tensile strength. Brominated epoxy in combination with antimony trioxide (Br/Sb) was compounded with both glass fiber reinforced PA6 and PA66. Br/Sb synergism was found to impart excellent flammability reductions in LOI value and UL-94 as V-0 rating. Effectiveness of Br/Sb flame retardant was also proven by the MLC measurements, which showed excessive reductions in PHRR and Total Heat Evolved (THE) values. On the other hand, Br/Sb shifted the degradation temperature 100&deg / C lower and decreased the tensile strength value, due to poor fiber-matrix adhesion and decreased fiber lengths. Red phosphorus (RP), when introduced to glass fiber reinforced PA66 induced V-0 rating in UL-94 together with significant increase in LOI value, and major decrease in PHRR. Degradation temperature was 20&deg / C lower while mechanical properties were kept at acceptable values compared to neat glass fiber reinforced PA66. In the second part of this dissertation, to investigate synergistic flame retardancy of nanoclays / glass fiber reinforced PA6 was compounded by certain nanoclay and an organo-phosphorus flame retardant (OP), which contains aluminum phosphinate, melamine polyphosphate and zinc borate, in a laboratory scale twin screw extruder. Exfoliated clay structure of the nanocomposites was assessed by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), while thermal stability and combustion behaviors were evaluated by TGA, LOI, UL-94 and MLC. Replacement of a certain fraction of the flame retardant with nanoclay was found to significantly reduce PHRR and THE values, and delay the ignition. Moreover, remarkable improvements were obtained in LOI values along with maintained UL-94 ratings. Residue characterization by ATR-FTIR and SEM ascribed the enhanced flame retardancy of nanocomposite specimens to the formation of a glassy boron-aluminum phosphate barrier reinforced by clay layers at the nanoscale.

In this thesis there were two main purposes, the first one being to investigate effects of zinc borate (ZB) on the flammability behavior of ABS when used with and without a traditional brominated flame retardant (BFR) / antimony trioxide (AO) system. The second purpose was to investigate contribution of nanoclays (NC) to the flame retardancy performance of the same traditional BFR compound with various combinations of AO and ZB again in ABS matrix. For these purposes, materials were melt compounded by using a laboratory scale twin-screw extruder, while specimens were produced by injection or compression molding. Flame retardancy of the specimens were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) measurements and UL-94 vertical burning tests. Other characterization techniques required in this thesis were / X-ray diffraction analysis, scanning and transmission electron microscopy, thermogravimetric analysis and tensile tests. Studies for the first purpose indicated that almost all flame retardancy parameters were preserved when antimony trioxide were replaced with zinc borate as much as in the ratio of 1:3. Residue analyses revealed that predominant flame retardancy mechanism of traditional system was gas phase action, while zinc borate contributes especially in the condensed phase action by forming thicker and stronger char layer. Investigations for the second purpose basically concluded that use of nanoclays improved all flame retardancy parameters significantly. Residue analyses pointed out that nanoclays especially contribute to the formation of stronger and carbonaceoussilicate char acting as a barrier to heat and flammable gases and retarding volatilization via tortuous pathway. As an additional third purpose in this thesis, usability of three boron compounds (zinc borate ZB, boric acid BA, boron oxide BO) with two traditional flame retardants (organic phosphinate OP and melamine cyanurate MC) in neat PET and recycled PET were also examined leading to some promising results in MLC parameters.