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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Thermally Induced Wrinkling Behaviour of Automotive Decorative Films

Malayery, Mazhary Mahdy January 2010 (has links)
<p>Decorative plastic films are becoming more and more popular in the industry, substituting paint, chrome-plating and hydrographics. Thermal formability of these films is extending the uses of these materials into newer applications within industry, but early observation have shown that certain film constructions will wrinkle upon heating. Despite growing interest and markets to use these films in thermal forming processes, there is insufficient knowledge in the field to explain or compensate for these undesirable surface wrinkles. The purpose of this study is to find out what caused the wrinkles, what the underlying behaviour was and if they could be avoided.</p> <p>The experiments were performed using a pressure sensitive adhesive coated decorative film, supplied by 3M Canada, which was laminated on one of two different secondary substrates (either steel or polypropylene). Samples were heated in a specially built hot stage with vacuum drawing capability at two different heating rates up to one of two final temperatures (110°C and 150°C) and cooled down at two different rates, afterwards. A CCD camera was used to track the changes in the wrinkle pattern on the surface of sample and relates its wavelength back to the corresponding transient temperature of the hot stage, which allowed on-line monitoring of wrinkle growth. Samples were cooled and then measured for their wavelength and surface roughness (represented by peak-to-valley distance (PV) and a standard roughness value, rms) using a white-light interferometer.</p> <p>Heating rate was found to be the dominant factor in controlling whether wrinkles occurred or not. Only with high heating rates did this wrinkle phenomenon occur regardless of the secondary substrate use, though the thermal conductivity of that substrate will impact this heating rate if heated from that side (which is what was being done in this work). For steel laminated samples, a chaotic zigzag wrinkles occurred using fast heating rates (around 95°C/min) which had an average equilibrium wavelength of 450 μm. Plastic laminates, just like their metal counterparts, developed wrinkles but now at high heating rates (170°C/min) which produced a pattern with an average wavelength of 550 μm. The slow heating rate (≈2°C/min) did not produce wrinkles for either substrate. Wrinkles are only the final outcome of thermally induced compression stresses which build within the film sandwich construction as the temperature rises and while slower heating didn't produce wrinkles, initial blister formation still occurred (i.e. nuclei of wrinkles) which increased the surface roughness of samples. Pre-straining a sample up to 20% elongation caused the wrinkle pattern to change from a complex biaxial pattern to longitudinal stripes, which extended the pattern always present along the edges of the sample into the centre of the test specimen.</p> <p>Of all models for the wrinkling behaviour of a thin film under compressive stresses in the literature, only one single model proposed by Basu et al. seemed to predict this behaviour reasonably by taking temperature and secondary substrate effects into account. All other models failed to predict this behaviour because, firstly they did not take the effects of temperature and secondary substrate into account, secondly, they<br />erroneously assume the film always deformed elastically, and thirdly, they are not well suited to the thickness ratio of film to substrate for our case.</p> / Master of Applied Science (MASc)

Environment-Responsive Paper-supported Membrane for Chromatographic Bio-separations: Preparation, Characterization and Application

Mah, Kor-Zheng January 2009 (has links)
<p>Environment-responsive paper-supported composite membranes, consisting of interpenetrating network of poly(<em>N</em>-vinyl caprolactam) and cellulose fibres, suitable for hydrophobic interaction membrane chromatography of proteins were prepared. These membranes could be made to switch between hydrophobic and hydrophilic states in a reversible manner by addition or removal of anti-chaotropic salts. A series of systematic studies were conducted to examine the effects of polymer loading and salt concentration on hydraulic and antibody binding properties of these membranes. A membrane possessing a satisfactory balance of hydraulic permeability and antibody binding was further examined for use in an immunoglobulin G (IgG) purification process. The membrane demonstrated low fouling tendency, satisfactory IgG binding (c.a. 12 mg/ml bed volume), and was successfully used for IgG purification from simulated cell culture supernatant. The results obtained demonstrate that the poly(<em>N</em>-vinyl caprolactam)-paper composite and indeed similar material could be used as inexpensive membranes adsorbers for protein purification.</p> / Master of Applied Science (MASc)

Temporal and Spatial Two-Medium Void Distributions by Radiation Diagnostics

Zakaib, Gary D. 04 1900 (has links)
<p>Two specific aspects of penetrating radiation diagnostics for application to two-phase flow systems were investigated. In Part I, discrete time interval attenuation measurements of a neutron beam from a research reactor were used to study the effect of the gating (measurement) period on the resulting void probability density distributions. Three idealized two-phase situations were investigated - discrete bubble, slug, and annular flow, for 0.01-10.0 s gating periods. The slug flow condition was readily characterized by a dual maxima PDD for gating intervals below the dominant slug period. In all cases the PDD variance increased with decreasing gating periods and was found to be of use for trend description and regime discrimination. Part II endeavours to reconstruct in two dimensions, the time-averaged void distribution of a dual density system from radiation attenuation measurements. The procedure employed made us of three contemporary algebraic reconstruction methods. Projection data was obtained from a digitized computer model in the first set of tests and later from traverses of a neutron beam across a voided lucite model. With a fixed, large beam size, decoupling of overlapped measurements was needed to permit resolution of fine detail. Extension to the dynamic two-phase flow situation was considered and it was shown that the void variance within a subdivided measurement interval can provide an estimate of the dynamic void bias effect.</p> / Master of Engineering (ME)

Processing and Properties of Biodegradable Polymer Blends Based on Gelatinized Potato Starch

Toosi, Falah Salma 02 1900 (has links)
<p>The development of environmental friendly polymers from renewable resources, specifically for short term packaging and disposable applications, has been recognized as an important alternative to synthetic polymer based packaging materials. In this work, we focus particularly on the use of potato starch, because there is a significantly large by-product stream of potato starch from potato waste after food processing in Canada.</p> <p>Poor processability and flowability are the main restrictions against the application of starch in granular form. Hence, thermoplastic starch (TPS) has been developed using starch in the presence of water and other plasticizers (e.g. glycerol) typically by using heat and shear. A microcompounder extruder was used for blending TPS, with an injection molding machine to prepare samples for testing. The sample test results show that TPS has severe limitations due to poor mechanical properties and high water sensitivity.</p> <p>To overcome the mentioned weaknesses, while maintaining material biodegradability, one method is to blend TPS with a high performance biodegradable polymer. Poly lactic acid (PLA) was added to TPS to improve the mechanical properties. The addition of PLA improved mechanical properties and reduced water sensitivity. In order to improve the compatibility between the main phases in the blend, maleic anhydride (MA) was grafted unto PLA as a reactive compatibilizer.</p> <p>Other methods to improve hydrophobocity and reduce water uptake were also investigated. Natural fiber reinforced TPS biocomposites were processed in order to improve blend performance and water sensitivity. For this purpose, sisal fiber was added to the TPS and TPS/PLA blends, and had major effects on the blend properties.</p> <p>The addition of paraffin wax was also investigated. The incorporation of paraffin wax also reduced the water sensitivity of the samples significantly and improved the mechanical properties compared to TPS only samples.</p> / Master of Applied Science (MASc)

The Use of Polyvinylamine-supported TEMPO Oxidation in Wet-strengthening of Paper

Ren, Pengchao 06 1900 (has links)
<p>Paper wet-strength is very important in many situations. Traditional wet strengthening agents such as formaldehyde-based resins and polyamide- epichlorohydrin (PAE) resins have been criticized to be a source of organochlorine compounds (l). This research aims at developing an efficient and environmental- friendly method to improve paper wet-strength. The new method combines the utilization of cellulose oxidation catalyzed by 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) and the application of a new commercialized polymer, polyvinylamine (PYAm).</p> <p>The TEMPO oxidation is known to introduce aldehyde and carboxyl groups on cellulose. In this research, an immobilized catalyst, polyvinylamine grafted TEMPO was synthesized and used for cellulose oxidation. The oxidation followed Anelli protocol, i.e. using NaCIO/NaBr as the primary oxidant. By using PVAm-TEMPO, we expect two advantages: a) upon adsorption onto fiber surfaces, PVAm-TEMPO could catalyze the oxidization locally and neighboring amines could then bond to the freshly formed aldehydes to impart strength. b) The oxidation catalyzed by immobilized TEMPO would be restricted to the exterior fiber surfaces because of the large size of PVAm-TEMPO. This will avoid the damage of fiber interior structures which is usually associated with free TEMPO oxidation and thus retain the fiber strength.</p> <p>Wet cellulose-to-cellulose adhesion was evaluated by measuring the force required to separate two wet cellulose films laminated with PVAm. Cellulose wet-strength could be improved from almost 0 to 40 N/m if oxidation and PYAm addition were combined in a proper way. Three methods were developed to do this, namely: direct coating method, adsorption method and one step method.</p> <p>Treatment conditions such as the optimum dosage of sodium bromide during oxidation and the best pressing temperature after PVAm application were investigated.</p> <p>The catalytic activity of PVAm-TEMPO was demonstrated by the oxidation of methylglyoxal (a water-soluble aldehyde) in a membrane catalyst reactor. The supported TEMPO showed high reaction activity.</p> / Master of Applied Science (MASc)

Dual Modifier Adaptation Methodology For the On-line Optimization of Uncertain Processes

Rodger, Eric 12 1900 (has links)
<p>The current industry standard in real-time optimization (RTO) is the two-step method. In this approach, mismatch between the plant and process model is compensated for by continuously updating a subset of the parameters in the process model. It is suitably resistant to measurement noise, however it is not guaranteed to move toward the plant optimum if structural plant-model mismatch exists. Due to this deficiency, a number of alternative methods have been developed over the years, including ISOPE and modifier adaptation. These methods, however, utilize plant derivative information, which must be estimated because a precise plant model is typically not known in practice. This makes these methods particularly susceptible to measurement noise. Therefore, in this thesis, the development of an RTO technology which is both optimum seeking and resistant to measurement noise is considered.</p> <p>This research can be separated into two parts. In the first phase, the current state-of-the-art modifier adaptation algorithm is modified by employing Broyden's method to estimate the plant output derivatives. A pair of deficiencies of Broyden's method are then detailed, and a modification to the algorithm, designed to mitigate these deficiencies, is proposed. This consists of the inclusion of additional constraints in the model-based optimization problem, designed to limit both offset and variance in the Broyden derivative estimates. Since the new algorithm possesses two distinct goals, optimality and the accuracy of the Broyden estimates, it is referred to as dual modifier adaptation.</p> <p>In the second phase of this research, the design of dual modifier adaptation systems is considered. The design methodology is built around the design cost criterion, a metric which had previously been developed for the two-step approach of RTO. The calculation procedure for the metric is adapted in this research in order to address dual modifier adaptation systems. In addition, an approach designed to compute the constraint back-off necessary to ensure a certain level of feasibility is developed.</p> <p>The concepts discussed in both the first and second phases of the research are illustrated using the Williams-Otto Reactor case study. This is a benchmark problem that has been used in the RTO literature for many years. A more involved case study, a propane furnace, is introduced in the last main chapter of this thesis. Both the performance of the dual modifier adaptation algorithm itself and the design of dual modifier adaptation systems are discussed for this case study.</p> / Master of Engineering (ME)

A Novel Approach for the Coordination of Block Decentralized Model Predictive Control

Salazar, Jorge Olvera Alberto 12 1900 (has links)
<p>In this thesis, a novel block decentralized MPC approach is implemented in order to coordinate the control of interacting process units (blocks) in a chemical plant. The goal of this research is to develop coordinated control that enables each block to optimize its own performance by adjusting only is manipulated variables while accounting for interactions among blocks.</p> <p>A simultaneous algorithm, termed D-MPC, is proposed that replaces multiple optimizations (from several, interacting MPC controllers) with one set of equations, yielding a single-level optimization problem. Given the complexity of the resulting problem consisting of linear and complementarity equations, an efficient active set heuristic is proposed for real time computations. The approach is computationally tractable, yielding a small set of convex problems to be solved sequentially and providing reliable solutions with good dynamic performance for the cases studied.</p> <p>Integrity is important for control designs, and generally, block designs with negative and zero Block Relative Gains (BRG) have poor integrity and cannot be controlled with published approaches. In contrast, the D-MPC approach successfully provides good integrity for processes with all BRG signs while maintaining the desired autonomy of each individual block.</p> <p>The solution existence, uniqueness, and stability of the proposed controller are also discussed in order to delimit what kind of processes can be controlled using the proposed D-MPC controller. A simple D-MPC formulation is analyzed to demonstrate that specific ranges of controller tuning can lead to the loss· of nominal stability for negative BRG systems. Therefore, a step-wise D-MPC design procedure was developed that integrates a stability analysis first proposed for centralized MPC and successfully adapted for the D-MPC controller.</p> <p>The dynamic performance and integrity demonstrated in case studies with all signs of BRG and sizes from 2x2 to 4x4 demonstrate the computational tractability, good dynamic performance of D-MPC controller designs developed with the design procedure and implemented with the heuristic algorithm.</p> / Master of Applied Science (MASc)

Studies of Labile polyelectrolyte at solid-liquid interfaces

Zhang, Liang 06 1900 (has links)
<p>p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times}</p> <p>Guar is naturally occurring polysaccharide. This thesis presents studies on hydroxypropyl guar (HPG) - borate, a Labile polyelectrolyte, interacting with a number of model tear film (eye) components including sulfate-stabilized polystyrene latex, anionic lipid-stabilized emulsions and cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes. The presence of borate ions converts nonionic HPG into an anionic polyelectrolyte. However, the borate ions on HPG chains do not inhibit HPG-borate adsorption onto anionic polystyrene latex. Both HPG and HPG-borate show the same adsorption isotherms. As a comparison, HPG slightly oxidized to give C6 carboxyl groups, with a degree of substitution close to HPG-borate, does not adsorb onto anionic polystyrene latex when the polymer is fully ionized.</p> <p>p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times} span.s1 {font: 11.0px Helvetica}</p> <p>Although HPG and HPG-borate do not adsorb onto anionic lipid-stabilized emulsions, the emulsions aggregate at high polymer concentration (> 0.1 g/L) because of depletion flocculation. Borate ions do not influence the depletion threshold polymer concentration. However, HPG provides gravitational stability for flocculated emulsions to against phase separation.</p> <p>p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times}</p> <p>Our work has shown that cationic colloids in the presence of HPG-borate display bridging flocculation, depletion flocculation, steric stabilization, salt induced</p> <p>coagulation, or no change at all, depending upon the HPG and salt concentrations. Developed were novel stability maps showing these phenomena mapped onto a log salt concentration versus log HPG concentration plane. The maps were generated by a combination of published models and experimental results. This portrayal of complex behaviors will be valuable to formulators because it clearly shows the effects of changing HPG molecular weight, colloids size and colloid volume fraction.</p> / Master of Applied Science (MASc)

Heat Exchanger Network Design, Monitoring and Optimization

Ati, Maheshwar Kiran Uma 08 1900 (has links)
<p>In process industries, heat exchanger networks represent an important part of the plant structure. The purpose of the networks is to maximize heat recovery, thereby lowering the overall plant costs. Previously published research on heat exchanger networks deals with two categories:</p> <p>• Synthesis of heat exchanger networks with the goal of designing a structure that provides the lowest total (capital plus operating) costs.</p> <p>• Data reconciliation with the goal of establishing true performance of the network and identifying correct heat transfer coefficients for individual exchangers in the network.</p> <p>Since heat exchanger models are highly nonlinear due to presence of log mean temperature difference term, solution of the network models is not always guaranteed. Most of the published results have used some form of approximation of the log mean temperature difference term. The approximations have been designed to provide reasonable accuracy while providing better convergence properties. Nevertheless, these are approximations and lead to the results that are not quite accurate. The goal of this research is to develop heat exchanger network models and algorithms for design, monitoring and optimization that are easy to implement in engineering practice and have excellent convergence properties.</p> <p>Presented here is a new heat exchanger network simulation algorithm which solves rigorously heat exchanger network equations in three phases:</p> <p>Phase 1: Solve mass balance equations for the network, i.e. determine flows in all branches of the network. These equations are linear.</p> <p>• Phase 2: Compute heat exchanger heat transfer factor for each exchanger in the network. Computation of the factor for each heat exchanger employs current flows through the exchanger and values of the exchanger variables at some base operating conditions.</p> <p>• Phase 3: Compute all heat exchanger outlet temperatures, given temperatures of the inlet streams and the results from Phase 1 and Phase 2. The computation in this phase is also employing a set of linear equations, while retaining full rigorous of the heat transfer equations.</p> <p>Hence, we have successfully transformed solution of a heat exchanger network into multi-phase solutions of sets of linear equations. This approach is then used for HEN synthesis and data reconciliation of HENs.</p> <p>HEN synthesis has been extensively studied over years and significant progress has been achieved in the development of robust methods for design of cost-optimal networks but one of the relatively less addressed issues is to deign HENs based on standard or modular sizes of heat exchangers. The major complexities in HEN synthesis are handling the combinatorial nature of the problem and finding a feasible and optimum solution using simultaneous synthesis methods. In this research, HEN simulation algorithm combined with differential evolutionary optimization is used for design of HENs with modular sizes of heat exchangers. This approach is successfully applied to examples available in the literature. Previously published results have used heat exchangers that have been sized for a placement at a specific location in a heat exchanger network, thereby aiming to provide the lowest cost solution. The research presented here shows that equally good or better solutions can be obtained by using standard, modular sizes of the heat exchangers. The approach used in this work is more realistic, since in practice heat exchangers are available in standards sizes, not custom made (in other words, a heat exchanger typically would have a size of 50 or 100 sq ft, but not 49.8 or 101.9 sq ft as may be calculated by the methods published in the literature).</p> <p>Data reconciliation and parameter estimation is an important step in HEN performance monitoring. In the current research, the HEN simulation algorithm is extended to develop a framework for data reconciliation of HEN and to estimate the change in the overall heat transfer coefficient of heat exchangers. This methodology is successfully implemented on two case studies from the literature.</p> / Master of Applied Science (MASc)

Engineering of Hyperbranched Polyethylene and its Future Applications

Haj-Abed, Mohammad 05 1900 (has links)
<p>The present study is concerned with the modification of hyper branched polyethylene (HBPE) via peroxide initiation and grafting with maleic anhydride. High-temperature solution modification using xylene as solvent was conducted, and the resultant material was characterized in terms of its structural, rheological, and physical properties, and compared to its unmodified counterpat. Moreover, the susceptibility of hyperbranched polyethylene to degradation/ crosslinking is investigated and compared to other commercially available polyolefins. Nevertheless, crosslinking of maleic anhydride grafted hyperbranched polyethylene is conducted in exploration of potential applications for this material.</p> <p>Peroxide initiated modification of hyper branched polyethylene was conducted to examine its vulnerability to degradation/ crosslinking relative to other commercially available polyolefins. Creep recovery was used to measure the percentage change in zero shear viscosity upon modification while <sup>13</sup>C-NMR was used to give the number of methyl, methylene, and methane groups. The work elucidated that the dominant reaction undergone by hyperbranched polyethylene upon peroxide initiated modification is degradation, in a fashion similar to polypropylene, which is due to its high degree of branching.</p> <p>Peroxide initiated grafting of hyper branched polyethylene with maleic anhydride was conducted and the effects of reaction time, reaction temperature, monomer concentration, initiator type, and initiator concentration were systematically examined. The structure of the resultant functionalized polymer was confirmed via FTIR and <sup>13</sup>C-NMR, and a maximal grafting density of 1.7 % was achieved using 2 wt.% MAH and 2 wt.% DCP in the preparation process. Alternating dominancy between the grafting reaction and other side reactions was noticeable when varying the initiator and the monomer concentrations. Moreover, a drop in the water contact angle upon modification suggested that the grafted polymer is more compatible with polar substrates. Furthermore, rheological characterizations showed that functionalized HBPE exhibits a Newtonian behavior, which is characteristic of its unmodified counterpart; however showed some slight shear thinning behavior at low temperatures.</p> <p>Crosslinking of HBPE-g-MAH using a diamine was conducted in solution and in melt in an effort to find a potential application for the resultant polymer. The structure of the resultant polymer was confirmed through FTIR and the effect of reaction time, reaction temperature, and diamine concentration on the degree of cross linking was investigated. A maximal degree of crosslinking of 70% was achieved, where the structure of the polymer was found to have tremendous effect on the concentration of diamine necessary to gel the polymer. Nonetheless, the formation of a soft solid material from two liquid reactants suggested that HBPE-g-MAH could be a potential material for reaction injection molding applications.</p> / Master of Applied Science (MASc)

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