Engineering Commons^™

Release Of Small Molecules From Rubber: Effects Of Materials Properties, Mechanical Loading And Molecular Interactions, Yongcan Du

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Release of small molecules from polymeric materials has wide applications in the delivery systems of active molecules such as drug, fragrance, and semiochemical. Rubber materials are good candidates for the excipients of those systems due to properties such as good flexibility, permeability, and biocompatibility. Factors like material properties, mechanical loading, and molecular interactions may affect the release of small molecules in those systems. Therefore, understanding how those factors affect the release is key to the formulation, design, and evaluation of those systems.

To study the effects of materials properties, vulcanized natural rubber sheets with different crosslink densities, loaded with small …

Cfrp Delamination Density Propagation Analysis By Magnetostriction Theory, Brandon Eugene Williams

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While Carbon Fiber Reinforced Polymers (CFRPs) have exceptional mechanical properties concerning their overall weight, their failure profile in demanding high-stress environments raises reliability concerns in structural applications. Two crucial limiting factors in CFRP reliability are low-strain material degradation and low fracture toughness. Due to CFRP’s low strain degradation characteristics, a wide variety of interlaminar damage can be sustained without any appreciable change to the physical structure itself. This damage suffered by the energy transfer from high- stress levels appears in the form of microporosity, crazes, microcracks, and delamination in the matrix material before any severe laminate damage is observed. This …

Glass Bubbles Grafted With Polymer Brushes For Liquid Hydrocarbon Fire Extinguishment, Randall Snipes

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The current most efficient solution to fighting liquid pool fires involves the use of firefighting foams containing fluorinated surfactants. The physiochemical properties of these foams are considerably different to all other currently available firefighting foams. Fluorinated surfactants lower the surface tension to a point where the foam solution draining from the foam structure forms a continuous aqueous film on the surface of a volatile hydrocarbon fuel, adding an additional barrier to fuel vapor diffusion to the burning fire. For this reason, these foams qualify as aqueous film forming foams (AFFFs). However, fluorinated compounds are extremely harmful for the environment due …

Mesoscale Modeling Of Controlled Degradation In Polymer Networks And Melts, Vaibhav Palkar

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Controlled degradation of polymers finds various applications in fields ranging from the design of functional soft materials to recycling of polymers. In several of these applications, the characteristic length scale at which relevant processes occur ranges from nanometers to microns, typically referred to as the mesoscale. Although analytical models and continuum approaches inform our current understanding, analysis of degradation at the mesoscale is exceptionally limited. For modeling degradation at the mesoscale, we use the Dissipative Particle Dynamics (DPD) technique and the LAMMPS simulation software. Within the DPD framework, we model controlled degradation or the breaking of covalent bonds within a …

Elucidating The Mechanical And Transport Properties Of Lignin-Based Hydrogel Composites, Nicholas Gregorich

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The use of lignin in the fabrication of soft composites has become an emerging area of research in polymer science and polymer chemistry. These lignin-based materials present numerous benefits, notably, a reduction in the use of petroleum-based precursor, improved structural benefits to otherwise soft host polymers, as well as the inherent antimicrobial and antioxidant properties of lignin, making it suitable for biomaterials. Herein, we present two chemical reaction pathways of incorporating lignin that was fractionated and cleaned using the Aqueous Lignin Purification with Hot Agents (ALPHA) process into poly(vinyl alcohol) (PVA) hydrogel composites for aqueous-based separations. By leveraging the ALPHA …

Enhancing The Performance Of Poly(3-Hexylthiophene) Based Organic Thin-Film Transistors Using An Interface Engineering Method, Eyob Negussie Tarekegn

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An original design and photolithographic fabrication process for poly(3-hexylthiophene-2, 5-diyl) (P3HT) based organic thin-film transistors (OTFTs) is presented. The structure of the transistors was based on the bottom gate bottom contact OTFT. The fabrication process was efficient, cost-effective, and relatively straightforward to implement. Current–voltage (I-V) measurements were performed to characterize the primary electronic properties of the transistors. The measured mobility of these transistors was significantly higher than most results reported in the literature for other similar bottom gate bottom contact P3HT OTFTs. The higher mobility is explained primarily by the effectiveness of the fabrication process in keeping the interfacial layers …

Design, Fabrication, And Characterization Of Conjugated Polymeric Electrochemical Memristors As Neuromorphic/Integrated Circuits, Benjamin Grant

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Organic materials are promising candidates for future electronic devices compared to the complementing inorganic materials due to their ease of processability, use, and disposal, low cost of fabrication, energy efficiency, and flexible nature toward implementation as flexible and non-conformal devices.With that in mind, electrochemical materials have been widely demonstrated with commercial use as sensors, displays, and a variety of other electronic devices. As Moore's law predicts the increase in the density of transistors on a chip, the requirement to create either smaller transistors or the replacement of the transistor device entirely is apparent. Memory resistors, coined ``memristor", are variable resistive …

Modeling Phase Behavior And Agglomeration In Polymer Systems Incorporating Complex Architectures: From Bottlebrush To Lysozyme, Sidong Tu

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Using computational modeling, we focus on the phase behavior of multicomponent systems incorporating enzyme and bottlebrush polymers where the agglomeration of multiple components occurs. We start with all-atom molecular dynamics (MD) simulations of lysozyme and polyethylene glycol (PEG) based polymer mixture to understand the mechanisms of preservation of lysozyme bioactivity at high temperatures with addition of PEG-derived bottlebrushes. We show that the PEG part of bottlebrushes phase separates at high temperature and shells the access of water to lysozyme, resulting in the preservation of lysozyme secondary structures. We then developed a coarse-grained model using a Dissipative Particle Dynamics approach to …

3d Printed Multicomponent Polymer Based Materials Via Hybrid Filaments: Fabrication And Characterization, Erik Antonio

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Additive manufacturing, also known as 3D printing, promises a manufacturing revolution for both industry and academic circles. One of the most widely used method of 3D printing is Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF), which requires a thermoplastic filament to be directed towards a heating block and then deposited via extrusion layer by layer to produce a finished part. However, there are significant issues with this technology, mainly a limitation on the materials available for use and mechanical property deficiencies when compared to traditional manufacturing. These issues are brought about by the temperature limited nature of the …

Modeling Pattern Formation And Morphology Development In Polymer Networks, Yao Xiong

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Topography and morphology have considerable impacts on the functionalities of soft materials in an entire range of applications from smart optics to tissue engineering. Adapting theoretical and computational approaches, we focus on the dynamics of pattern formation and morphology development in polymer networks. This dissertation starts with studying the dynamical control of pattern formation in confined thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) gel films. The patterns are formed due to mechanical instabilities. We perform a linear stability analysis and identify the limits of this analysis in predicting pattern formation in gels. We then study the restructuring between patterns and hysteresis phenomena …

Extractive Membranes For The Detection And Screening Of Waterborne Plutonium, James Foster

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The development of rapid screening tools for special nuclear materials remains a crucial focus for nonproliferation efforts. Traditional approaches for the analysis of trace-level Pu isotopes in water requires tedious and time-consuming sample preparation steps that do not lend well to expeditious screening. Therefore, a novel analytical method that combines both Pu concentration and source preparation into a single detection system would make for an invaluable tool for nuclear security applications. Extractive membranes absorbers can help to fulfill this role as they are capable of concentrating Pu to detectable limits while subsequently serving as alpha spectrometry sample sources. In Chapter …

Synthesis And Molecular Processes Governing Self-Healing Polymeric Materials, Siyang Wang

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Self-healing polymers capable of recovering from physical damages are promising materials for advanced technologies. In these studies, we developed routes to achieve self-healable properties in acrylic-based copolymers that rely on non-covalent dipolar interactions present in essentially all polymeric materials. Using a combination of spectroscopic tools, thermo-mechanical analysis, and molecular dynamic (MD) simulations, these studies have shown that dipolar interactions lead to conformational changes of macromolecular segments which, in turn, result in self-healing without external intervention. This dissertation also describes the development of novel self-healable acrylic-based covalent adaptable networks (CANs) that combine reprocessing and self-healing properties. The utilization of dipolar interactions …

Synthesis Of Monodisperse Nanoscintillators At High Temperatures For Biomedical Relevant Applications, Eric Zhang

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Luminescent sub-100 nm particulates continuously generate immense research interest in the biomedical field for imaging, theranostics, and optogenetics. Conventionally, upconversion nanoparticles or UV activated semiconductors are studied, however these materials are limited by biological barriers such as the skin which reduces the penetration depth of these excitation sources, tissue's auto- fluorescence, and toxicity. One approach to overcome these challenges is to use nanoscintillators (sub-100 nm materials that can generate visible light using high energy excitation sources such as x-rays) which can generate light locally to the human body. Numerous scintillators have been reported since the discovery of x-rays from the …

Sustainable Composites From Agricultural And Petroleum Waste, Menisha S. Karunarathna

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Green gas emission has been a pervasive and persistent subject of debate for a prolonged period. The soaring number of industries and vehicle fuel emissions presage a concomitant rise in global CO₂ emissions. Global cement production is responsible for 8% of the total CO₂ release, yet, the production continues due to the surging demand. Hence, there is an ongoing quest to find alternatives for cement and building materials produced with zero to lower CO₂ emissions. The work presented in this dissertation focuses on finding recyclable, zero CO₂ gas-producing high sulfur biocomposites materials, which can compete with …

Understanding Process-Structure-Property-Performance Relationships Of Thermoplastic Olefins (Tpo) Foams Through A Novel Manufacturing To Response Pathway, Sai Aditya Pradeep

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The global transportation industry is the second highest contributor to climate change. As a result, there has been a concerted effort to spearhead research in economical lightweighting technologies, as every 10 % reduction in weight will lead to to 6 – 8 % improvement in fuel efficiency. Additionally, the recent push for electrification and the emphasis on Corporate Average Fuel Economy (CAFE) standards have seen original equipment manufacturers (OEM’s) dive into lightweighting of materials to improve overall range and/or fuel-efficiency. Thermoplastic Olefins (TPOs) have in recent years carved out a niche in the automotive industry due to advantages such as …