Polymer and Organic Materials Commons^™

Active Response Of Polymer Materials From External Stimuli – Solvents And Light; Grafting Reactions On Perovskite Layers, Jianxia Zhang

University of New Orleans Theses and Dissertations

The active response of a series of polymeric materials was investigated. Both solvent activated and light activated thin films and wire systems show dynamic behaviors when exposed to different stimuli.

Solvent mediated fluxional behavior of polymer thin films involved extensive, rapid curling both on infusion and evaporation of good solvents. These films can be either lab-fabricated ones or commercial ones, and the curling behavior can be as fast as seconds. Conditions including polymer materials, chosen solvents, and film geometry can affect the behavior.

Methods that allowed for the creation and retention of distorted wire structures were also developed; the asymmetric …

Advanced Design Optimization For Composite Structure: Stress Reduction, Weight Decrease And Manufacturing Cost Savings, Shayan Ahmadian

Master's Theses

An injection moldable chopped fiber composite actuator with detailed drawing and tolerances was designed within one year. A vendor was selected and a quote for injection molding tooling cost for production was obtained and the first prototype was built in addition of six months. The risks are identified and material characterization tests are proposed.

The objective of this project was redesigning an aluminum made actuator with a continuous fiber composite for weight saving purposes. After searching the literature and consulting with experts in the field it was concluded that manufacturing costs associated with continuous fiber composite are 3 times as …

Nanocharacterization Of Porous Materials With Atomic Force Microscopy, Yasemin Kutes

Master's Theses

Scanning Probe Microscopy techniques have proven very useful in the investigation of porous nanostructured surfaces. Especially, Atomic Force Microscopy (AFM) has been widely used due to its compatibility with non-conducting surfaces. In particular, AFM often complements other techniques like scanning and transmission electron microscopy by providing quantitative surface information coupled with nanoscale spatial resolution. Its ability to operate in fluid is also important, as this allows researchers to mimic the physiological environment of biological materials and systems. In this work, two main types of porous materials are studied with AFM, including Phosphoric Acid Fuel Cell (PAFC) electrode catalyst layers, and …

Tuning The Properties Of Metal-Ligand Complexes To Modify The Properties Of Supramolecular Materials, Ian Henderson

Open Access Dissertations

Supramolecular chemistry is the study of discreet molecules assembled into more complex structures though non-covalent interactions such as host-guest effects, pi-pi stacking, electrostatic effects, hydrogen bonding, and metal-ligand interactions. Using these interactions, complex hierarchical assembles can be created from relatively simple precursors.

Of the supramolecular interactions listed above, metal-ligand interactions are of particular interest due to the wide possible properties which they present. Factors such as the denticity, polarizability, steric hindrance, ligand structure, and the metal used (among others) contribute to a dramatic range in the physical properties of the metal-ligand complexes. Particularly affected by these factors are the kinetic …

Surface Instabilities For Adhesion Control, Chelsea Simone Davis

Open Access Dissertations

Controlling the specific adhesive properties of surfaces is a technologically complex challenge that has piqued the interest of many research groups around the world. While many scientists have used complex topographic and chemically altered surfaces to tune adhesion, others have shown that naturally occurring phenomena, such as elastic instabilities, can impact adhesion. We provide a thorough investigation into the effects of periodic surface buckling instabilities, or wrinkles, on adhesion. Wrinkles are an attractive surface patterning alternative as they form spontaneously over large areas and their dimensions, namely wavelength and amplitude, can be controlled on length scales relevant for adhesion control. …

Cross-Linked Pdms Expansion Due To Submersion In Liquid And Supercritical Co2, Teng Yang

Graduate Theses and Dissertations

Characterization of micro/nano-copper particles impregnated Polydimethylsiloxane (PDMS) submersed in supercritical carbon dioxide (scCO2) was studied. The purpose of this investigation was to advance micro-corrosion sensor technology utilizing PDMS and micro-metal particle composite as the sensing element currently under-development. One of the key challenges encountered was the removal of the native oxides inherently existing on the metal particles. Numerous techniques were experimented with to counter this problem at the UA Engineered Micro/Nano Systems Laboratory (EMNSL), with swell-based protocols being identified as the most promising solution. In terms of compatibility to Micro-electro-mechanical Systems (MEMS) fabrication, CO2 is often used in the release …

Electrospun Polycaprolactone Nanofiber Scaffolds For Tissue Engineering, Andreas Haukas

Graduate Theses and Dissertations

Stem cell and tissue engineering offer us with a unique opportunity to research and develop new therapies for treating various diseases that are otherwise incurable using traditional medicines. However, development of these new therapies replies upon the establishment of in vitro cell culture and differentiation systems that mimic in vivo microenvironments required for cell-cell and cell-ECM interaction. The development of these cell culture systems depends upon the identification of appropriate biomaterials and cell sources. Biomaterials should be carefully selected and fabricated into scaffolds for supporting cell growth and differentiation. In this study, we explored the fabrication of 3D electrospun nanofiber …

Thermodynamic Analysis Of Polyethylene Glycol Thiol-Ene Click Chemistry And Surface Modification Of Bacterial Cellulose, Kaan Serpersu

Masters Theses

Polyethylene glycol (PEG) has been one of the extensively studied polymers for medical applications. However, the use of PEG can require complicated and low efficiency reactions which can impose limits to potentially useful medical solutions. Click chemistry has recently emerged as a way to avoid these pitfalls by utilizing reactions that are highly efficient and require simple reaction conditions. One such reaction is known as the Michael-addition thiol-ene click reaction (TECC). The combination of PEG with TECC has received some study, but has not been thermodynamically characterized as a click reaction. In this work PEG-TECC reaction kinetics were studied by …

Physiochemical And Nanomanipulation Studies Of Carbon Nanomaterials, Siva Naga Sandeep Chalamalasetty

Graduate Theses and Dissertations

Carbon nanomaterials are, without a doubt, one of man's wonder creations. Though these nanomaterials are a very recent trend, extraordinary electromechanical properties and the light weightiness of these nanomaterials attracted the attention of researchers. Although vast research has been done since the start of the US nanotechnology initiative, much effort was in the area of synthesis and characterization of the nanomaterials. However, most of the traditional macroscopic material's theories fail at the nanoscale level, and since the material properties are dependent on size and structure at nanoscale level, the behavior of the carbon nanomaterials in different environments needs attention. High …

A Conductivity Testing System Coupled With A Tensile Testing Machine To Measure The Surface Properties Of Polymer Specimens, Nguyen T. Nguyen

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Polymers play an essential role in our everyday life due to their employment in a widespread range of applications. Polymers are used in industries such as space, biomedical, electronics, etc. in which their electrical and mechanical properties are major aspects which need to be investigated prior to implementation. When subjected to mechanical stimulations, polymers may exhibit changes in electrical conductivity which can vary locally within the specimens, especially in those of conducting polymers. In mechanical investigations a tensile testing machine is used to understand polymers’ strength, elasticity or other mechanical properties. In electrical analysis, using a four-point probe to examine …

The Implementation Of A Visco-Hyperelastic Numerical Material Model For Simulating The Behaviour Of Polymer Foam Materials, Conor Briody, Barry Duignan, Stephen Jerrams, John Tiernan

Articles

Polyurethane foam has been in use for some time in wheelchair seating systems as it offers good pressure relieving capabilities in most cases. However, little characterisation work has gone into seating foam materials by comparison with conventional elastomeric materials. Accurate material models could allow better prediction of foam in-service behaviour, which could potentially improve seating design practises. The objective of this work was to develop an approach for the validation of hyperelastic and viscoelastic material model parameters used to simulate polyurethane foam behaviour. Material parameters were identified from relevant test procedures and implemented in a Finite Element simulation of an …

Response Characterization Of Electroactive Polymers As Mechanical Sensors, G. Alici, Geoffrey M. Spinks, J. D. Madden, Y. Wu, G G. Wallace

Gursel Alici

The characterization of the dynamic response (including transfer function identification) of trilayer polypyrrole (PPy) type conducting polymer sensors is presented. The sensor was built like a cantilever beam with the free end stimulated through a mechanical lever system, which provided displacement inputs. The voltage generated and current passing between the two outer PPy layers as a result of the input was measured to model the output/input behavior of the sensors based on their experimental current/displacement and voltage/displacement frequency responses. We specifically targeted the low-frequency behavior of the sensor as it is a relatively slowsystem. Experimental transfer function models were generated …

Biomedical Properties And Preparation Of Iron Oxide-Dextran Nanostructures By Maple Technique, Carmen Steluta Ciobanu, Simona Liliana Iconaru, Eniko Gyorgy, Mihaela Radu, Marieta Costache, Anca Dinischiotu, Philippe Le Coustumer, Khalid Lafdi, Daniela Predoi

Chemical and Materials Engineering Faculty Publications

Background: In this work the chemical structure of dextran-iron oxide thin films was reported. The films were obtained by MAPLE technique from composite targets containing 10 wt. % dextran with 1 and 5 wt.% iron oxide nanoparticles (IONPs). The IONPs were synthesized by co-precipitation method. A KrF* excimer laser source (λ = 248 nm, τFWHM≅25 ns, ν = 10 Hz) was used for the growth of the hybrid, iron oxide NPs-dextran thin films.

Results: Dextran coated iron oxide nanoparticles thin films were indexed into the spinel cubic lattice with a lattice parameter of 8.36 Å. The particle sized calculated was …

Capillary Force In High Aspect-Ratio Micropillar Arrays, Dinesh Chandra

Dinesh Chandra

High aspect-ratio (HAR) micropillar arrays are important for many applications including, mechanical sensors and actuators, tunable wetting surfaces and substrates for living cell studies. However, due to their mechanical compliance and large surface area, the micropillars are susceptible to deformation due to surface forces, such as adhesive force and capillary force. In this thesis we have explored the capillary force driven mechanical instability of HAR micropillar arrays. We have shown that when a liquid is evaporated off the micropillar arrays, the pillars bend and cluster together due to a much smaller capillary meniscus interaction force while still surrounded by a …

Morphology And Properties Of Nylon 6 Blown Films Reinforced With Different Weight Percentage Of Nanoclay Additives, Raghavendra R. Hegde Dr

Raghavendra R Hegde Dr

This article presents the effect of increasing weight percentage natural nanoclay additives on the structure, morphology and mechanical properties of nylon-6-blown films. Combination of X-ray diffraction, thermal analysis and microscopy were used to determine nanocomposite film morphology. The nanoclay additives in the films act as nucleating agent facilitates γ-crystalline forms and results in fine grained spherulite with smaller lamellar size. Increase in tensile, burst, and tear strength is observed for films with up to 5% clay loading. Even though microscale property like tensile and tear strength drops at higher add on levels, near-surface nanoscale hardness and toughness of the film …

Controlling Morphology In Swelling-Induced Wrinkled Surfaces, Derek Breid

Open Access Dissertations

Wrinkles represent a pathway towards the spontaneous generation of ordered surface microstructure for applications in numerous fields. Examples of highly complex ordered wrinkle structures abound in Nature, but the ability to harness this potential for advanced material applications remains limited. This work focuses on understanding the relationship between the patterns on a wrinkled surface and the experimental conditions under which they form. Because wrinkles form in response to applied stresses, particular attention is given to the nature of the stresses in a wrinkling surface. The fundamental insight gained was then utilized to account for observed wrinkle formation phenomena within more …

Carbon Nanotubes Grown On Glass Fiber As A Strain Sensor For Real Time Structural Health Monitoring, Matthew Boehle, Qiong Jiang, Lingchuan Li, Alexandre Lagounov, Khalid Lafdi

Chemical and Materials Engineering Faculty Publications

In order to more effectively monitor the health of composite structures, a fuzzy fiber sensor has been developed. The fuzzy fiber is a bundle of glass fibers with carbon nanotubes or nanofibers (CNTs or CNFs) grown on the surface. The nanotube coating makes the fiber bundle conductive while the small conductive path increases sensitivity. The fuzzy fiber sensor can replace conventional metal foil strain gauges in composite applications. The electrical response of the sensor is monitored in real time to measure strain, vibration, cracking and delamination. Continuous monitoring provides instant notification of any problems. Implementation of this sensor network in …

Insights Into The Power Law Relationships That Describe Mass Deposition Rates During Electrospinning, Jonathan J. Stanger, Nick Tucker, Simon Fullick, Mathieu Sellier, Mark P. Staiger

Jonathan J Stanger

This work explores how in electrospinning, mass deposition rate and electric current relate to applied voltage and electrode separation, factors give a range of applied electric fields. Mass deposition rate was measured by quantifying the rate of dry fibre deposited over time. Electric current was measured using a current feedback from the high voltage supply. The deposition of fibre was observed to occur at a constant rate for deposition times of up to 30 min. Both the mass deposition rate and electric current were found to vary with the applied voltage according to a power law. The relationship between the …

Design Mixers To Minimize Effects Of Erosion And Corrosion Erosion, Julian B. Fasano, Eric E. Janz, Kevin J. Myers

Chemical and Materials Engineering Faculty Publications

A thorough review of the major parameters that affect solid-liquid slurry wear on impellers and techniques for minimizing wear is presented. These major parameters include (i) chemical environment, (ii) hardness of solids, (iii) density of solids, (iv) percent solids, (v) shape of solids, (vi) fluid regime (turbulent, transitional, or laminar), (vii) hardness of the mixer's wetted parts, (viii) hydraulic efficiency of the impeller (kinetic energy dissipation rates near the impeller blades), (ix) impact velocity, and (x) impact frequency. Techniques for minimizing the wear on impellers cover the choice of impeller, size and speed of the impeller, alloy selection, and surface …

Manipulation Of Electrospun Fibres In Flight: The Principle Of Superposition Of Electric Fields As A Control Method, Nurfaizey A. Hamid, Jonathan J. Stanger, Nick Tucker, Andrew Wallace, Mark P. Staiger

Jonathan J Stanger

This study investigates the magnitude of movement of the area of deposition of electrospun fibres in response to an applied auxiliary electric field. The auxiliary field is generated by two pairs of rod electrodes positioned adjacent and parallel to the line of flight of the spun fibre. The changes in shape of the deposition area and the degree of movement of the deposition area are quantified by optical scanning and image analysis. A linear response was observed between the magnitude of movement of the deposition area and voltage difference between the auxiliary and deposition electrodes. A squeezing effect which changed …