Master of Science, University of Akron, 2016, Mechanical Engineering

The modern rubber industry is always in pursuit of improvements in the properties of the final product resulting from the mixing of the rubber compounds with different fillers and additives. Depending on the functional characteristics of the final product and thus the compounding ingredients, different types of mixers can be used for the rubber mixing process. Hence, the choice of an appropriate mixer is critical in achieving the proper distribution and dispersion of fillers in rubber, and a consistent product quality, as well as is the attainment of high productivity. Besides rotor design, operational parameters such as speed ratio and the orientation of the mixing rotors with respect to each other also play significant role in the mixing performance. With the availability of high-performance computing resources and high-fidelity computational fluid dynamics tools, understanding the flow field and mixing characteristics associated with rotor orientations, speed ratios and complex rotor geometries, has become more feasible over the last two decades. As part of this effort, all the simulations here are carried out in a 75% fill chamber with two counter-rotating rotors using a CFD code. In the phase angle and rotor design studies conducted here, the rotors rotate at 20 rpm even speed, whereas for speed ratio study, only the left rotor rotates at 20 rpm and the right rotor rotates at a speed, which is a multiple of 20 rpm by the speed ratio specified. The computational models used in this research are based on a finite volume method to simulate a partially filled mixer equipped with different tangential rotor types. The model solves for transient, isothermal and incompressible set of governing fluid equations for the mixing of non-Newtonian high-viscosity rubber. The research here considers phase angles of 45°, 90° and 180°, speed ratios of 1.0, 1.125 and 1.5, and rotor designs including 2-wing, 4-wing A and the 4-wing B rotors. Investigation of each parameter type (open full item for complete abstract)

Committee: Abhilash Chandy Ph.D. (Advisor); Povitsky Alex Ph.D. (Committee Member); Choi Jae-Won Ph.D. (Committee Member) Subjects: Fluid Dynamics; Industrial Engineering; Mechanical Engineering; Polymers

Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

New processes and development of advanced technologies are essential for society to progress. The polymer field is vast and further expanding with the creation of new techniques and products. An advanced extrusion processing technique that has been beneficial in creating new products with very interesting properties takes the form of multi-layer co-extrusion. Initially multi-layer co-extrusion was and, in some cases, still is limited by the number of layers that can be achieved, the properties of different polymers can be combined to form products that are superior in different aspects due to the material selection. Layer multiplying co-extrusion was developed to achieve high layer numbers with the use of typically only two to three extruders. This work examines the layer multiplication technique capabilities for highly filled polymer layered systems and annular structures for pipe and blow molding applications. Limited work has been performed with filled polymer systems with using the layer multiplication technique. This work examines a model system to investigate effects of fillers at high loading levels on the stability of the layer structures created. The interface between filled and unfilled layers was examined xix to see the effect of particles at the interface. Along with this, particles with different rigidities were examined to investigate the effect of changing the rigidity of particles in confinement on the mechanical properties of the overall films. Previous work examined the creation of a tubing die for the layer multiplication technique to achieve high layer number annular structures. This work utilizes this tubing die to examine how angular rotation of the outer wall of the die land effects the weld line presence and pressure properties of the resultant tubes. The development of annular structures also allows for creation of blow molded structures. This work examines blow molding of high layer number bottles using a simple tabletop set-up and the (open full item for complete abstract)

Committee: João Maia (Committee Chair); Ica Manas-Zloczower (Committee Member); Gary Wnek (Committee Member); Alp Sehirlioglu (Committee Member) Subjects: Plastics

Master of Science, University of Akron, 2023, Mechanical Engineering

Recent advancements in polymer science and manufacturing have made market interest for Gradient Refractive Index (GRIN) lens technology grow exponentially. At the forefront of this field, Peak Nano is developing a process to engineer lenses for a variety of applications from medical to defense [1]. In the compression molding process step of manufacturing a GRIN lens, it is required to heat the polymer laminate above Glass Transition Temperature (Tg). This is currently achieved by conduction and convection heating of a charge inside the molding tool. Due to the poor thermal properties of polymers, a long transient is required for the charge to reach steady state. Additional difficulty is involved with GRIN laminates as the material properties are different for each layer. As stakeholder, Peak Nano would benefit from a shorter transient and improved thermal uniformity at steady state. Optical transmission data collected for the GRIN material blends indicated potential in heating via infrared (IR) radiation. A novel IR heating method was then developed for comparison to the conventional strategy. Results of this model gave improved heating time and uniformity over the current process. From there, a simulation matrix was generated, and the most successful setup was presented as a viable replacement to the conventional process.

Committee: Guo-Xiang Wang (Advisor); Ali Dhinojwala (Committee Member); Sadhan Jana (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering; Optics; Plastics

Doctor of Philosophy, Case Western Reserve University, 2021, Macromolecular Science and Engineering

The step polymerization reaction between diisocyanates and diols results in a tremendously functional material with wide-ranging applications including medical devices and sealants, known as thermoplastic polyurethane (TPU). The microphase separation of urethane-rich hard segments (HS) and hydrocarbon soft segments (SS) provide TPU with the unique morphology responsible for its elastomeric properties. The structure-property relationships of TPU have been understood in terms of either a rubber-like material where HS-rich regions act as crosslink points or a nanocomposite where hard regions are the reinforcing agent. In both views, attempts to model the mechanical behavior based on morphology are hampered by the difficulty in determining parameters that describe the morphology from the chemical composition. The distribution of HS block length and the attractive hydrogen bonding forces make predicting the morphology using block co-polymer theory imprecise, especially for low HS content (HSC) TPUs. Furthermore, TPU has typically been viewed as a binary system with a hard phase dictated by the HSC and a soft phase whose properties are only dependent on the diol type and molecular weight. The first part of this thesis challenges the binary view of TPU through an experimental and modeling investigation. An analytical micromechanical model, the Eshelby double inclusion model, was used to evaluate the observed mechanical behavior of a series of polyester TPUs with increasing HSC, a series of polyether TPUs softened by triols in the SS, and a series of polyester TPUs softened by triol chain extenders. The model was used to probe the mechanical reinforcement contribution from morphological parameters. The TPU morphology was modeled as a composite of HS-rich “hard particles” and a SS-rich “soft matrix”, with the necessity of a third, intermediary phase, the “interphase” evaluated based on experimental results. The second part of the thesis goes beyond neat TPU by prepa (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor); Donald Feke (Committee Member); Michael Hore (Committee Member); Gary Wnek (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

The nature of glassy aging has been a topic of study for over half a century, and yet a number of open questions remain in the understanding of the glassy state. Since a polymer's physical and mechanical properties are directly dependent on its molecular structure and changes in that structure alter the physical properties of the glass, considerable economic impact can result from aging-related physical changes. Characterization of aging dynamics in under-dense and over-dense glasses and a comparison of the aging response in solvent-processed vs thermally-quenched glasses are two important questions that are addressed here. This work reports on the development of a protocol for studying physical aging via molecular dynamics simulation after a near-instantaneous temperature quench. The resulting data display characteristic experimental signatures of glassy aging in both a pure polymer and a polymer-plasticizer system, indicating that this protocol can potentially be used to study aging in a variety of systems. Results indicate that aging dynamics in under-dense and over-dense glasses are fundamentally different in character. Unlike in under-dense glasses, translational dynamics in over-dense glasses are mechanistically different than relaxation in equilibrium glass-forming liquids, which is supported by the finding that relaxation in over-dense glasses occurs through an explosive burst of superdiffusive motion. Addition of a plasticizer appears to moderate this response compared to that of the pure polymer system, which can be attributed to a decrease in system fragility in the plasticized system. Higher additive loadings may have an even greater effect and further research would be beneficial in clarifying this. Aging relaxation time in over-dense glasses obeys a zero parameter dependence on purely equilibrium properties. This finding enables prediction of non-equilibrium relaxation time given knowledge only of the starting temperature and the in-equilibrium (open full item for complete abstract)

Committee: David Simmons (Advisor); Kevin Cavicchi (Committee Chair); Ruel McKenzie (Committee Member); Mark Foster (Committee Member); Jutta Luettmer-Strathmann (Committee Member) Subjects: Condensed Matter Physics; Engineering; Polymers

Doctor of Philosophy, Case Western Reserve University, 2020, Macromolecular Science and Engineering

As society evolves and technology develops further, the need for more advanced products is increasing, so polymeric materials are gaining ever more attraction because of their excellent properties such as lightweight, low cost and good resistance to corrosion. Polymer processing is one of the keys to achieve these unique materials. Various kinds of morphologies can be produced during polymer melt compounding including droplet-matrix, fibrillar, lamellar, or co-continuous structures. Co-continuous morphology, which has the coexistence of two continuous structures within the same volume, has been drawing more attention currently because of its specific superior properties including a combination of the features of both components in a favorable way, as well as additional characteristics by selectively localizing fillers in the co-continuous structures. Since processing-structure-property relationships are guiding principles in materials design, development, and tailoring, it is important to study them in co-continuous polymer blends and composites. In chapter 1 of this dissertation, the formation and properties of co-continuous blends and double-percolated co-continuous composites are introduced. In chapter 2, the formation of co-continuous poly(ethylene) oxide/ethylene-vinyl acetate blends as well as the effects of structure and processing on their surface roughness are explored. Moreover, two thermally conductive co-continuous ternary composites systems are reported in chapter 3. The role of viscosity ratio on filler distribution and electrical/thermal properties of the carbon nanofiber reinforced co-continuous polymer composites is discussed, along with the discussion of the effects of filler sizes on morphology and thermal conductivity of double-percolated polypropylene/poly(methyl methacrylate)/boron nitride polymer composites. Furthermore, two additional projects are demonstrated in chapter 4 and chapter 5. Chapter 4 compares the fiber length distributi (open full item for complete abstract)

Committee: Joao Maia (Advisor); Ica Manas-Zloczower (Committee Member); Svetlana Morozova (Committee Member); Donald Feke (Committee Member) Subjects: Polymers

Doctor of Philosophy, Case Western Reserve University, 2019, Macromolecular Science and Engineering

This dissertation has a primary focus on design and development of composites by employing processing methods aimed at improving filler dispersion in polymers. Mixing elements taking advantage of extensional dominated flows are adopted. Several such mixing elements, extensional mixing elements (EMEs) to be specific, with varying degree of ability to impose extensional dominated flows, have been experimentally validated. A first attempt is made to enhance the dispersion of carbon black (CB), graphene nano platelets (GNP) and carbon nano tubes (CNT) in polypropylene (PP). Enhanced dispersion does translate into improved mechanical properties. A more comprehensive approach is adopted with an integrated computational and processing method on thermoplastic polyurethane (TPU) graphene oxide (GO) composites. The role of filler functionalization in exfoliation and TPU hard block crystallization is established. A difference in anisotropy and phase separation is observed between material processed with EME and kneading blocks. A significantly enhanced ductility is obtained by employing EME during processing. Improved abrasion and strength is also observed. A secondary focus of the thesis includes synthesis of composites by wet chemical and other processes to end up with composite materials with enhanced properties and/or improved material behavior. Hydrogels of poly(ethylene glycol) methyl ether methaycrylate filled with graphene oxide are made via a reversible assisted fragmentation termination (RAFT) approach. Reinforcement and lubrication effects are studied with the incorporation of covalent bonds between filler and matrix. Aerogels obtained from hydrogels of graphene oxide (GO) and montmorillonite (MMT) clay nanocomposites in poly(vinyl alcohol) are synthesized. Hence, obtained aerogels have improved compressive strength and further silylation makes them functional materials for oil-water separation. Twin-screw reactive extrusion of Thermoplastic polyureth (open full item for complete abstract)

Committee: Joao Maia (Advisor); Manas-Zloczower Ica (Committee Member); Dai Liming (Committee Member); Lewandowski John (Committee Member) Subjects: Analytical Chemistry; Chemistry; Design; Engineering; Materials Science; Nanoscience; Nanotechnology; Polymer Chemistry; Polymers

Master of Science, University of Akron, 2015, Physics

Cellular membranes are complex assemblies and a clear understanding of the physical interactions during their function is of paramount importance. Here, we perform two separate studies for a better understanding of the interactions between membrane compartments and other biomolecules. In the first study, we developed a coupler to integrate a high sensitivity spectrometer with an epi-fluorescence microscope to measure fluorescence spectra of small area samples (400 micrometer squared). We applied our measurements on standard samples, performed three corrections on them and after a linear demixing process, the percentage of FRET efficiency was obtained. The development of this method will be advantageous in future single cell studies for detecting population heterogeneity. In the second study, we investigated the dynamics of membrane lipids in a supported lipid bilayer. Single particle tracking total internal reflection fluorescence microscopy (TIRF) was used to study the lateral mobility of phosphatidylinositol phosphate (PIP) lipids with and without an adsorbed polycationic polymer, quaternized polyvinylpyridine (QPVP). Diffusion coefficients were determined with Brownian and anomalous models. Our results indicate a decrease in diffusion coefficient of the lipids in the presence of QPVP in comparison to its absence, revealing their interaction.

Committee: Adam Smith (Advisor); Jutta Luettmer-Strathmann (Committee Chair); Sergei Lyuksyutov (Committee Member) Subjects: Biophysics; Chemistry; Physical Chemistry; Physics

Doctor of Philosophy, University of Toledo, 2010, College of Engineering

Poly(ethylene Terephthalate) (PET) is a prominent packaging material which is widely used in the plastic packaging industry. When compared with traditional packaging materials, such as steel and glass, the oxygen barrier property of PET is moderate at ambient temperature. The moderate oxygen barrier property of PET limits the application of PET for packaging some oxygen sensitive products, such as beer. Several approaches have been made to enhance “shelf life” of PET packaging material, especially for oxygen sensitive foods. The active barrier packaging technique, which absorbs oxygen during its permeation route into packaged article, was studied in this research. Unsaturated hydrocarbons were used to modify PET to develop an oxygen scavenging system which can react with oxygen as an oxygen scavenger. In this research the unsaturated hydrocarbon is low molecular weight hydroxyl terminated polybutadiene. After the modification, the modified PET should maintain the favorable properties of PET and have an oxygen scavenging capability. The reason for blending hydroxyl terminated polybutadiene (HTPB) and PET was that the hydroxyl end group of HTPB was expected to react with end groups of PET to form a copolyester. The PET/HTPB copolyester will have different optical, thermal and mechanical properties than those of a unreacted PET/PBD physical blend. In this research, the oxidation mechanisms and kinetics of pure polybutadiene was studied first. Factors such as the molecular weight and composition of polybutadiene, which can affect oxidation mechanisms and kinetics, were analyzed. Activation energies of unsaturated olefin groups in the oxidation reactions were obtained. In the second portion of this research, low levels of hydroxyl terminated polybutadiene were reactively extruded with PET to form a polybutadiene modified PET. The oxidation kinetics and mechanism of this polybutadiene modified PET were also studied. Factors that can affect oxidation kinetics, such as th (open full item for complete abstract)

Committee: Saleh A. Jabarin PhD (Committee Chair); G. Gleen Lipscomb PhD (Committee Member); Maria R. Coleman PhD (Committee Member); Isabel C. Escobar PhD (Committee Member); Yong Wah Kim PhD (Committee Member) Subjects: Chemical Engineering; Materials Science; Polymers

Doctor of Philosophy, The Ohio State University, 2009, Chemical Engineering

Nanotechnology is continually becoming more integrated into consumer products used by the general public on a daily basis. Consumers reap the benefits of enhanced properties for these commercial products, and yet they are still affordable. For biomedical products, that include nanofeatures, this is not yet a reality. The materials and methods used to fabricate these products are still far too expensive. There are many inexpensive and commercially available polymers that have potential to be used in these advanced biomedical products, but the fabrication techniques still lack the simplicity required to create an inexpensive end product.Supercritical CO2 has been used to overcome the polymeric nanofabrication barriers for high throughput production of biomedical devices. Novel CO2-assisted low temperature polymer nanoprocessing fabrication techniques have been implemented for use in biomedical product creation. Polymer nanofabrication techniques such as bonding, imprinting, and active biomolecule immobilization were demenonstrated. Due to being CO2-assisted techniques, these processes are intrinsically inexpensive and environmentally benign. In order to thoroughly investigate these nanofabrication techniques the interactions between CO2 and the polymer were examined on a thermodynamic level. Thermodynamic modeling results of high pressure CO2/polystyrene systems were used along with experimental bonding, imprinting, and immobilization results. It was found that the solubility of CO2 in a polymer matrix and the resulting reduction of the polymer glass transition temperature (Tg) largely dictate the polymer chain mobility and therefore the polymer's processability. For instance, it was shown that the polymer bond strength of polystyrene, bonded via a CO2-assisted technique, depended largely on the proximity of the processing conditions to the reduced Tg curve. It was also found that low aspect ratio nanofeatures could be patterned by CO2-assisted nanoimprint lithography (open full item for complete abstract)

Committee: David Tomasko (Advisor); L. James Lee (Committee Member); James Rathman (Committee Member); Sherwin Singer (Committee Member) Subjects: Chemical Engineering

Master of Science, The Ohio State University, 2008, Industrial and Systems Engineering

In co-injection molding process, two different polymer melts are sequentially injected into a mold to form a part with a skin/core structure. Co-injection molding can be used among other applications for recycling, improving barrier and electrical properties. The basic characteristics of a co-injection molded product depend on the properties of the skin and core layers, and the skin/core volume ratio. This thesis presents a study of the effect of molding parameters on material distribution and mechanical properties of co-injection molded plates. The plates were molded with polypropylene(PP) and thermoplastic olefin(TPO) as skin and core. Four molding parameters-injection velocity, skin and core temperature, and core percent-were varied. Core percent was the most significant factor influencing core breakthrough. After the injection molding process reached steady state, molded samples were collected and cut to measure the core volume ratio using an optical microscope. Mechanical properties, such as flexural and impact strength show a good correlation with the core content. This thesis also compares the experimental results to numerical simulations using Moldflow Plastic Insight. Results for our simple mold show a good agreement between experimentals and simulations.

Committee: Jose Castro (Advisor); Allen Yi (Committee Member) Subjects:

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

In this work, new CO2-selective membranes were synthesized and their applications for fuel cell fuel processing and synthesis gas purification were investigated. In order to enhance CO2transport across membranes, the synthesized membranes contained both mobile and fixed site carriers in crosslinked poly(vinyl alcohol). The effects of crosslinking, membrane composition, feed pressure, water content, and temperature on transport properties were investigated. The membranes have shown a high permeability and a good CO2/H2 selectivity and maintained their separation performance up to 170°C. One type of these membranes showed a permeability of 8000 Barrers and a CO2/H2selectivity of 290 at 110°C. The applications of the synthesized membranes were demonstrated in a CO2-removal experiment, in which the CO2 concentration in retentate was decreased from 17% to < 10 ppm. With such membranes, there are several options to reduce the CO concentration of synthesis gas. One option is to develop a water gas shift (WGS) membrane reactor, in which both WGS reaction and CO2-removal take place. Another option is to use a proposed process consisting of a CO2-removal membrane followed by a conventional WGS reactor. In the membrane reactor, a CO concentration of less than 10 ppm and a H 2concentration of greater than 50% (on dry basis) were achieved at various flow rates of a simulated autothermal reformate. In the proposed CO2-removal/WGS process, with more than 99.5% CO2 removed from the synthesis gas, the CO concentration was decreased from 1.2% to less than 10 ppm (dry), which is the requirement for fuel cells. The WGS reactor had a gas hourly space velocity of 7650 h-1 at 150°C and the H2 concentration in the outlet was more than 54.7% (dry). The applications of the synthesized CO2-selective membranes for high-pressure synthesis gas purification were also studied. We studied the synthesized membranes at feed pressures > 200 psia and temperatures ranging from 100-150 °C. The effects of (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

In this work, a new methodology is developed that describes the viscoelastic scaling of a polymer – physical foaming agent (PFA) solution in a detailed and internally consistent manner. The approach is new in that while previous researchers have largely focused on scaling down experimentally obtained high pressure polymer-PFA solution viscosity data onto a master curve for the viscosity of the undiluted polymer melt at a reference temperature and atmospheric pressure, we have generated the shear viscosity data required for our simulations by systematically scaling up the viscosity values obtained through a single set of experiments on the undiluted pure polymer melt at atmospheric pressure. Using the above data, simulations were run for the flow of a polymer – PFA solution through an extrusion foaming die with an abrupt axisymmetric contraction. The pressure drops across the die obtained through the simulations showed good qualitative agreement with experimental pressure drop measurements on the foaming extrusion die obtained previously in our laboratory. Field values of pressure, temperature and velocity were obtained at each point in the foaming die. Once the values of pressure and temperature were obtained along each point in the foaming die, classical nucleation theory for bubble nucleation, in the form developed originally by Zeldovich, was invoked to predict the local bubble nucleation rate downstream of the saturation surface. The hydrodynamic constraints to the nucleation rate were calculated using Kagan's extension of the Zeldovich theory. Diffusional constraints were incorporated into the theory using the method suggested by Katz and his coworkers. The capillarity approximation was found not to be valid for bubble nucleation of CO2 in polymers; a correction on the lines suggested by Tolman was applied to get non-zero nucleation rates for the system.

Committee: Kurt Koelling (Advisor) Subjects: Engineering, Chemical

Doctor of Philosophy, The Ohio State University, 2004, Chemical Engineering

Supercritical CO2 is a promising solvent for application in polymer blending and foaming. The addition of small amounts of compressed gases to polymer phases results in substantial and sometimes dramatic changes in the physical properties that dictate processing. Interfacial tension is a key parameter in determining the bubble nucleation and growth rates, as well as droplet break up in blending. However very limited data on this property is available in the literature for CO2-polymer systems. A novel technique is presented to determine the interfacial tension for the polymer melts and high pressure CO2 systems by analysis on the axisymmetric pendant drop shape profile, which can simultaneously yield the density, swelling and interfacial tension results. The method avoids the “capillary effect” and the “necking effect” and provides good axisymmetry of the pendant drop, which makes it a suitable method for measuring the interfacial tension for polymer melts under high pressure CO2 conditions. The interfacial tension between polymer melt (PS, PP, PLGA, PMMA) and high pressure CO2, and the interfacial tension between polymer melt pairs (PS/PP) saturated with high pressure CO 2 were studied using the pendant drop method in a high pressure, temperature view cell. CO 2 was found to significantly depress the interfacial tension in the pressure range studied. The linear gradient theory combining with the Sanchez-Lacombe Equation of State was applied in predicting the surface tension or interfacial tensions for polymer melts under high pressure CO2 conditions, which correctly predicts the depression of interfacial tension by high pressure CO2 and yields reasonable agreement with experimental data. The role of CO2 in enhancing the polymer blending process was carried out based on the Capillary Number, which is the most important parameter governing the drop breakage and coalescence in the blending process and thus the morphology of the blends. A highly simplified population ba (open full item for complete abstract)

Committee: David Tomasko (Advisor) Subjects: Engineering, Chemical

Doctor of Philosophy, The Ohio State University, 2002, Industrial and Systems Engineering

Reactive in-mold coating (IMC) products have been used successfully for many years to improve the surface quality of Sheet Molding Compound (SMC) compression molded parts. IMC provides a smooth, sealed surface, used as a conductive or nonconductive primer for subsequent painting operations. The success of IMC for SMC parts has recently attracted the interest of thermoplastic injection molders. The potential environmental and economic benefits of using IMC as a primer and, in the ideal case, to replace painting completely are large. Acceptance of IMC as a competitor to the traditional painting processes will depend upon the improvement of its ability to deliver in-mold coated parts in short cycle times at the highest possible quality level. Most optimization studies in Reactive Polymer Processing involve compromising between different performance measures since, frequently, the controllable variables have conflicting effects on these measures. IMC is not the exception to the rule. The performance measures need to be balanced, each against the other, in order to obtain the best compromises. The goal of this research work is to develop an optimization strategy for the application of reactive in-mold coating to SMC and thermoplastic parts in presence of multiple and conflicting performance measures. To achieve this goal we explore the use of Artificial Neural Networks as metamodeling techniques and the use of Data Envelopment Analysis to solve multiple criteria optimization problems.

Committee: Jose Castro (Advisor) Subjects:

Master of Science (MS), Ohio University, 2009, Mechanical Engineering (Engineering and Technology)

The thermal design of a nanocomposite mold for the blow molding process has been studied. For low production cycles, there is a significant interest in using lower cost composite molds to replace the expensive traditional metal molds used in the blow molding process. A critical issue in using a polymer matrix composite as an alternative to a metal for mold material is the large difference in the thermal transport properties. The composite mold design must integrate enhanced cooling so that the product can cool sufficiently within a short cycle time. Nanocomposites that use carbon nanofiber offer improvements in thermal and mechanical properties; therefore they are potential candidates for making molds for polymer products. This project describes the design of a nanocomposite blow mold using numerical simulations of the thermal transport in the mold and the stress analysis of the final blow molded product.

Committee: Khairul Alam PhD (Advisor); Hajrudin Pasic PhD (Committee Member); Peter Klein PhD (Committee Member); Xiaoping Shen PhD (Committee Member) Subjects: Mechanical Engineering; Plastics; Polymers

Doctor of Philosophy, Case Western Reserve University, 2010, Macromolecular Science and Engineering

Polyhedral oligosilsesquioxane (POSS)-based biodegradable polymers were investigated as stent coating for drug delivery from drug-eluting stents and as polymeric scaffold for fully bioabsorbable stents. A highly efficient and precise electrospraying technique, one of the electrostatic processing techniques, was developed for the stent coating application. The roughness of stent coatings produced was varied conveniently by the electrospraying technique utilizing different electrospraying mode or Coulombic fission, and was further modified using post-treatments of pure solvent electrospraying or vapor welding. Abluminal stent coatings were achieved utilizing the targeting nature of the charged electrospraying droplets to avoid luminal coating on stents by applying nonconductive materials temporarily contacting the inner surface of the stents.Long-standing questions of paclitaxel (PTx)-polymer blend miscibility and interactions were studied for particular polymer blends using characterization methods. It was found that paclitaxel is amorphous in all proportions in the blends of paclitaxel with POSS-based thermoplastic polyurethanes (POSS TPUs), and serves as an antiplasticizer by increasing the blend Tg gradually from the polymer Tg up to the substantially higher Tg of amorphous paclitaxel. The polyethylene glycol (PEG) segment incorporated in POSS TPUs exhibited specific hydrogen-bonding interactions with the paclitaxel and promoted the miscibility in the blends. Highly adjustable release of paclitaxel was achieved from both thermoplastic stent coatings utilizing P(DLLA-co-CL)-based POSS TPUs, and thermoset stent coatings employing PLGA-POSS end-linked thiol-ene network. Using a newly-developed drug release approximation model describing the entire drug release profile, paclitaxel release mechanisms from these biodegradable stent coatings were interpreted quantitatively, including the effects of polymer glass transition temperature, polymer initial molecular weight, (open full item for complete abstract)

Committee: Patrick T. Mather (Advisor); Gary E. Wnek (Committee Member); Lei Zhu (Committee Member); Horst A. von Recum (Committee Member) Subjects: Biomedical Research; Polymers

Doctor of Philosophy, Case Western Reserve University, 2006, Macromolecular Science

Fluidic Systems are present in a variety of fields and applications and multiscaling analysis is an important tool both at the macroscopic scale for the optimization of industrial processes, such as mixing colorants in a polymer matrix or mixing of gases in an engine, as well as at the microscopic level when dealing with microfluidics such as micro-reactors and micro-mixers. In this thesis a multiscaling approach to the analysis of the efficiency of mixing of fluidic systems for multi-component flows is developed and a microstructure characterization based on the concept of multi-fractal behavior is introduced. Generically, mixing is a unit operation that involves manipulating a heterogeneous physical system with the intent to make it more homogeneous. The concept of entropy as the measure of the level of homogeneity of a system is applied and various ways to employ the entropy to characterize the state of mixing in a multi-component system at different scale of observations are explored. Computer simulations of fluidic systems are employed to trace the motion of passive tracers used to visualize the behavior of the fluids and to evaluate the overall mixing efficiency. First the quality of such approach on commonly known systems, such as extruder devices and microchannels, is verified then the use of chaotic advection as a tool to increase mixing efficiency is introduced. To create a time dependence of the flow field, necessary to induce chaotic behavior, a non periodic patterning of one of the walls of the systems is proposed, such that the three components of the velocity field are coupled. The behavior of those chaotic systems is shown to generate interfaces with fractal structures. Since fractal and multi-fractal characteristics can be of great interest in relation with the material properties of the final compound a quantification of this multiscale property is done by calculating the generalized fractal dimensions. There is a certain correspondence between mix (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2004, Macromolecular Science

Mixing is an important component in most processing operations including but not limited to polymer processing. Generically, mixing refers to a process that reduces composition nonuniformity. Since the entropy is the rigorous measure of disorder or system homogeneity, in this work we will explore various ways to employ the entropy to characterize the state of mixing in a multi-component system. The various species can be initially present in the system or they can evolve as a result of a dispersive mixing operation involving a cohesive minor component. Computer simulation of agglomerate dispersion and sequential distribution of all particles obtained in the system allows us to evaluate the overall mixing efficiency of processing equipment. Evaluation is based on a specific mixing index, calculated using the Shannon entropies for different size fractions. The index can be tailored to give preference to different particle size distributions, thus relating the quality of mixing to specific properties of the final product. We propose a Shannon entropy based index of color homogeneity to assess color homogeneity as well as deviations from a standard/ideal color. We illustrate the concept by analyzing ABS polymeric samples obtained in a single screw extruder by mixing blue and yellow polymer pellets. Alternatively the proposed technique can be employed to assess the efficiency and degree of distributive mixing attained in polymer processing equipment. We present numerical simulations for an ABS resin extrusion in an industrial conventional single screw extruder. Based upon the flow field patterns obtained in the simulations, a particle tracking procedure was employed to obtain information about the spatial distribution of particle tracers of two colors. Results of the simulation were compared with experimental data obtained under similar extrusion conditions. To evaluate the degree of color mixing and color homogeneity for the system, we also employ the entropy based inde (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor) Subjects: Plastics Technology

Doctor of Philosophy, Case Western Reserve University, 1995, Macromolecular Science

Continuous mixing equipment is widely used in polymer processing. Typical continuous mixers include single screw and twin screw extruders. The flow field in these mixing devices is difficult to analyze due to the complex geometry. In this work, a fluid dynamics analysis package-FIDAP, using the finite element method, was implemented to simulate the three dimensional, isothermal flow patterns in the region of conveying elements and shearing discs of a Leistritz intermeshing counterrotating twin screw extruder model LSM30.34, a 2′′ Welding Engineers tangential counterrotating twin screw extruder and the MCT section of a Multi-Cut Transfermix extrusion system. The rheology of the fluid was described by a power-law model. The problem of time dependent flow boundaries was solved by selecting a number of sequential geometries to represent a complete mixing cycle. The dispersive mixing in the region of conveying elements and shearing discs of the intermeshing counterrotating twin screw extruder was characterized in terms of shear stresses generated in the flow field and a parameter β quantifying the elongational flow components. The influence of screw rotational speed and axial pressure difference on these flow characteristics was analyzed. Comparisons of the flow characteristics in the regio n of conveying elements and in the shearing discs, and between corotating and counterrotating modes in the shearing discs were also presented. A framework was developed to evaluate distributive mixing efficiency in the intermeshing and tangential counterrotating twin screw extruders and in the Multi-Cut Transfermix. The dynamics of distributive mixing was studied numerically by means of tracking the evolution of particles originally gathered as clusters. The extent or goodness of mixing was characterized in terms of length stretch, pairwise correlation function and volume fraction of islands. The length stretch reflects the capability of the mixer to spread particles away from their n (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor) Subjects: Plastics Technology