Although glass containers are an everyday item the process responsible for their production is not scientifically understood. Developments have occurred slowly over many years, mostly on a trial and error basis and in response to economic pressures. The narrow neck press and blow (NNPB) process has evolved in recent years as a result of attempts to reduce container weight. The fundamental component of the NNPB process is the plunger which is responsible for the initiation of the cavity and control of glass distribution within the container. The NNPB plunger functions as a form tool and as a heat exchanger, thus requiring a carefully selected range of properties. The Engineer responsible for tooling selection and operation has a limited resource of scientific knowledge to enable the performance of the process to be optimised. The current NNPB plunger is subject to high rates of wear and is directly responsible for product defects, thermal instability and limits process speed. The work presented here is a scientific study of current NNPB plunger technology. The plunger has been investigated in relation to the requirements of the glass container forming process. The materials used have been examined, before and after use and their wear modes explained. The thermal properties of the plunger have, as far as is possible, been examined during the forming cycle. When combined with results from the characterisation of transformations occurring in the material, during its service life, operational requirements have been explained. The ability of the NNPB plunger to remove heat from the glass has been investigated, and has illustrated significant deficiencies in the current arrangement. Details are given as to how these deficiencies may be overcome to enable the Engineer to regain control of the process. As a result of the study many phenomena exhibited by the NNPB plunger are now understood and may be related to the performance of the process.

A range of antioxidants (BHT, Irganox 1010, 1076, 1330 and Irgafos 168) were incorporated into polymers (polyethylene, polypropylene, polystyrene and polyvinyl chloride) and subjected to increasing doses of gamma-irradiation (1,5,10,20,25,35 and 50 kGy) from a cobalt-60 source. The amount of extractable antioxidant from the stabilised polymers was determined chromatographically and a gradual diminution in the total extractable levels of each antioxidant was observed as irradiation progressed, the extent depending on the nature of both the antioxidant and the polymer 2,6-Di-t-butyl-1,4-benzoquinone was shown to be an extractable degradation product, arising from the effects of gamma-irradiation on the phenolic antioxidants. The extractable degradation product arising from the phosphite antioxidant, Irgafos 168, was identified as tris(2,4-di-t-butylphenyl)phosphate. It was demonstrated using 14C-labelled Irganox 1076 that degradation products formed during gamma-irradiation are becoming covalently bound to the polymer, as a result of radical coupling processes. There is a pronounced increase in the extent of covalent binding from 0.4% before irradiation to a minimum of 12.4% after an exposure to 50 kGy. Evidence has also been presented of covalent binding of the degradation product of Irgafos 168 to the polypropylene matrix, via polymeric radicals formed during irradiation. Finally, the effects of gamma-irradiation on the extent of migration of antioxidants from polyolefins into food simulants was studied. It was found that irradiation leads to a decrease in the extent to which hindered phenolic antioxidants migrate from polyolefins into fatty media, consistent with the reduction in extractable antioxidant levels and the increase in the extent of antioxidant-polymer binding.

Adhesion aspects of laminated aluminium/polyester systems have been studied before and after mechanical deformation. The work has been carried out in collaboration with a producer of beverage cans, and the reasons for the adhesion reduction observed during the deep drawing and wall ironing process has provided the focal point for the work. Laminates were manufactured from commercial polyester film and commercially anodised (2 types) or chromium phosphated aluminium coil stock. The morphology of the pretreated aluminium surfaces has been investigated by using scanning electron microscopy. The chemical composition and the composition variation with depth of the pretreated aluminium surfaces have been studied by XPS sputter depth profiling. It is found that the CP and PAAI, PAAII pretreatments have reduced the amount of magnesium in the top layer of aluminium surfaces. An intimate contact between the polyester film and the aluminium substrate of the laminates and the thicknesses of the pretreated layers have been observed by cross- sectional TEM following sample preparation by chemical sample thinning and microtoming. Based on angle resolved XPS and SIMS investigation, the locus of failure of the can systems produced from the CP and PAAI treated aluminium has been defined as within the polyester film but very near the interface. The thickness of the residual polyester overlayers has been estimated. A peel test has been used to evaluate the adhesion level of the cans. The order of the adhesion level of the cans produced from different surface pretreated aluminium has been found to be; PAAII > CP > PAAI. Chemical exposure methods have been established to make the investigation of interfacial surfaces of the laminates possible by SEM. A shear lag analysis has been carried out to demonstrate the mechanical deformation behaviour of the laminates during the deep drawing and wall ironing process. A relationship between the thickness of the pretreated layer and the fragment size has been proposed. It is found that the pretreated layer fragment characteristics is very important. Fine and uniformly distributed fragments with small separation distance in the aluminium substrate of the cans contribute to the adhesion level through crack pinning effect. A comprehensive model for adhesion loss during deep drawing and wall ironing process has been proposed.

M.Tech.

Newtown Pippin and Winesap apples were taken from terminal storage, and prepared as slices to be processed in re-tortable pouches to determine an optimum process using the relatively new pouch technology. Preprocessing treatments included calcium chloride as a texture modifier, sodium bisulfite as a microbial inhibitor and colour stabiliser, and sodium acid pyrophosphate as a colour stabilizer. These reagents were added to the slices by vacuum infusion, hot blanching or cold dipping to determine their effects on the final product. The slices were packed in 300 gram pouches that were evacuated, then flushed with either nitrogen or carbon dioxide before sealing. The samples were stored at 22 and 35°C and were examined by physical, chemical and sensory methods, at intervals of two weeks, six weeks and five months after processing to determine the changes occurring within the samples. During storage, quality changes did occur, which affected the acceptance of the samPles/ particularly at the higher temperatures. Texture was vastly improved with the addition of calcium ions to old apples. Colour remained significantly lighter in samples with higher SO₂ levels. The addition of pyrophosphate was also shown to increase the lightness of the samples. The levels of reducing sugars and pH were shown to increase with the length and temperature of storage. Preparatory methods were also shown to have a great influence on the quality of the final product. Hot blanching of apple slices lead to a lower quality product than either vacuum infusion or cold dipping. Vacuum infusion was by far the most efficient preparatory method but resulted in a product with a translucent appearance and a bland flavour. Cold dipping produced the best final product. The use of carbon dioxide atmospheres within the pouch produces a lower pH and a softer texture in the samples. Nitrogen was found to be the better of the two gases for quality maintenance. In general, it was determined that apples from terminal storage were more difficult to process into a product of good quality than were apples stored for only a short time after harvest. / Land and Food Systems, Faculty of / Graduate

No description available.

The reason for confusion in grocery stores is the fact that many of the same types of food products are being marketed with different labels. Many packaging labels contain keywords such as “organic,” “farm fresh,” and “all natural.” Some products incorporate the use of images such as a picturesque farm or a “happy” cow. Using data collected from the surveys of 349 college students, this study examines student choices of food products based on organic and non-organic and brand and generic foods. Variables also examined include sex, health, and living arrangements. The results of this study can help provide an understanding about the mindset of the average college student while shopping at the grocery store. Based on the results there is evidence that students are significantly more likely to choose food products that are non-organic and generic. Based on the five variables used, sex and concern for nutritional value were the most significant in predicting a student’s purchase of brand and organic food products, while body mass index, frequency of looking at nutritional facts labels, and living arrangement were not significant.

Power electronic systems and components that can operate in environments with ambient temperatures exceeding 250 °C are needed for innovation in automotive, aerospace, and down-hole applications. With the imminent mass electrification of transportation and industry, the high-temperature electronics market value is anticipated to grow to $15 billion by the end of 2023. Conventionally, silicon (Si)-based converters are used in these applications; however, as operating temperatures continue to increase, the inherent limits of these systems are being met. The primary limitations for the high-temperature operation of semiconductor devices is the intrinsic carrier concentration, dictated primarily by the bandgap of the material, which increases with temperature. Wide-bandgap (WBG) power semiconductors, primarily silicon carbide (SiC) and gallium nitride (GaN), have been adopted for use in these applications, but exhibit a degradation in performance at elevated temperatures. As such, gallium oxide (Ga2O3), an ultrawide-bandgap (UWBG) material with controllable doping and the potential for inexpensive substrates, has presented itself as a potential contender for use in high-temperature power electronics applications. The UWBG of Ga2O3, 4.8 eV compared to 1.1 eV for Si, 3.2 eV for SiC, and 3.4 eV for GaN, allows it to achieve nearly 1033 lower intrinsic carrier concentration than Si, permitting Ga2O3 power devices to theoretically operate at significantly higher temperatures. In addition, unipolar Ga2O3 devices have a better theoretical limit with respect to the relationship between on-resistance and breakdown voltage, which could enable higher power density and power conversion efficiency. While Ga2O3 exhibits potential in these regards, its low thermal conductivity (11–27.0 W/m·K compared to 148 W/m·K for Si, 350 W/m·K for SiC, and 130 W/m·K) means that standard packaging and cooling techniques are not suitable or effective. Furthermore, conventional polymeric and organic encapsulant materials are typically limited to operating temperatures of 200 °C and novel materials must be evaluated. This work outlines and evaluates an electro-thermal device-package co-design modeling platform that can be utilized for the efficient and accurate modeling of Ga2O3 devices and their associated packaging, with the goal of overcoming the challenges of the low thermal conductivity of Ga2O3. This permits for the electrical and thermal performance of the devices and the package to be designed in tandem for an effective design. Next, six high-temperature encapsulation materials are evaluated and conclusions are drawn about each material's feasibility for use as a dielectric encapsulation material for a power module operating at temperatures exceeding 250 °C. This simulation platform and material analysis was then used to design and fabricate a 300 °C, 1.2 kV half-bridge power module utilizing Ga2O3 diodes to assess thermal and electrical performance. / Master of Science / Power electronic systems and components that can operate in environments with ambient temperatures exceeding 250 °C are needed for innovation in automotive, aerospace, and down-hole applications. With the imminent mass electrification of transportation and industry, the high-temperature electronics market value is anticipated to grow to $15 billion by the end of 2023. Conventionally, silicon (Si)-based converters are used in these applications; however, as operating temperatures continue to increase, the inherent limits of these systems are being met. The primary limitations for of the high-temperature operation of semiconductor devices is the intrinsic carrier concentration, dictated primarily by the bandgap of the material, which increases with temperature. Wide-bandgap (WBG) power semiconductors, primarily silicon carbide (SiC) and gallium nitride (GaN), have been adopted for use in these applications, but exhibit a degradation in performance at elevated temperatures. As such, gallium oxide (Ga2O3), an ultrawide-bandgap (UWBG) material with controllable doping and the potential for inexpensive substrates, has presented itself as a potential contender for use in high-temperature power electronics applications. This work outlines and evaluates an electro-thermal device-package co-design modeling platform that can be utilized for the efficient and accurate modeling of Ga2O3 devices and their associated packaging, with the goal of overcoming the challenges of the low thermal conductivity of Ga2O3. This permits for the electrical and thermal performance of the devices and the package to be designed in tandem for an effective design. Next, six high-temperature encapsulation materials are evaluated and conclusions are drawn about each material's feasibility for use as a dielectric encapsulation material for a power module operating at temperatures exceeding 250 °C. This simulation platform and material analysis was then used to design and fabricate a 300 °C, 1.2 kV half-bridge power module utilizing Ga2O3 diodes to assess thermal and electrical performance.

A new design protocol and energy absorption models are proposed for polymeric foam that improve material and absorber geometry selection for impact conditions encountered in service. Design diagrams are constructed that show the energy absorption of uniaxial and trapezoidal absorber geometries as a function of product geometry, foam density, and strain rate for closed cell polyethylene (PE) and polystyrene (EPS) packaging foams. Design constraints including load spreading, buckling, creep, and material costs are addressed. Energy absorption models for plate, cylindrical, and spherical product geometries generate design data that account for the increased stress and energy absorption resulting from deformation of foam adjacent but external to the region directly below the product (i.e., load spreading). The models partition the energy absorption into polymer deformation and gas compression components, require only easily obtainable uniaxial compression data, and agree within fifteen percent of measured values. Additionally, a systematic examination of the effect of processing parameters on EPS fracture and energy absorption characteristics addresses the influence of cracks frequently observed in impacted commercial EPS components. The energy absorbed during compression increases with increasing toughness because compression induced fracture is reduced. Lower fracture toughness allows longer cracks, which decreases the energy absorbed, possibly resulting in damage to the packaged product. The toughness increases as a function of increased molding time and pressure because of increased fusion. Fusion is characterized by quantitative fractography and is correlated with toughness.

The multi-component acrylate photoresist investigated in this dissertation consists of a linear polyacrylate copolymer, a photo-polymerizable multi-functional acrylate monomer, a ketone photo-initiator, an amine crosslinking agent and a certain amount of inorganic filler. Three distinct phases have been observed in this multi-component system by transmission electron microscopy (TEM)--the flake-like inorganic filler, the monomer-rich droplet inclusion and the polymer-rich matrix. Selected area diffraction (SAD) has determined the crystalline structure of the filler phase and the amorphous structure of the matrix phase. It has also concluded that the diffraction rings in the monomer-rich inclusion phase come from the filler polycrystals. After the photoresist is fully cured by UV radiation followed by thermal baking, distinct spots in the dimension of 100 A have been observed in the monomer-rich inclusion phase. The subsequent thermal curing process increases the mobility of the molecules and provides sufficient time for the molecules to aggregate and form distinct micro-phases in the monomer-rich inclusions. In the mean time, the filler crystals grow larger and distinct diffraction rings and spots can be seen in the SAD pattern. In contrast to the phase-separate morphology of the multi-component photoresist, only one broad glass transition has been observed by DSC, DMA and dielectric relaxation experiments. The broad glass transition reflects the inhomogeneity of local composition and the heterogeneous network structure of the material. The structure-property relationship of the multi-component photoresist as a function of curing history has been investigated. The residual stress and mechanical properties of the acrylate photoresist processed under various curing conditions have been characterized, and the curing mechanism has also been investigated. The increased glass transition temperature, modulus and ultimate strength of the material indicate that either ultraviolet radiation or thermal baking partially cures the photoresist. However, FTIR studies suggest that the two curing methods generate different network structures through independent crosslinking mechanisms. Both curing methods are required to fully cure the acrylate photoresist and achieve the desired coating properties. It has been found that the curing sequence plays an important role in determining the final network structure and material properties of the thermoset coating. (Abstract shortened by UMI.)