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735 full-text articles. Page 1 of 28.

Plasticization And Reinforcement In A Boron Cage Compound Polyurethane Nanocomposite: A Dielectric Study, J. Liu, X. Zhang, D. E. Bowen, Nicola Bowler 2017 Iowa State University

Plasticization And Reinforcement In A Boron Cage Compound Polyurethane Nanocomposite: A Dielectric Study, J. Liu, X. Zhang, D. E. Bowen, Nicola Bowler

Nicola Bowler

In order to control and modify the physical properties of nanocomposite systems, it is essential to understand the nano-filler/polymer structure–property relationships. Boron cage compounds (BCCs) are a class of icosahedral, closed cage molecules that are of interest due to their high boron content, their inherent neutron absorbing/shielding properties, their potential ability to act as molecular nano-particles and their ability to significantly improve the thermal stability of polymers in which they have been incorporated. When the BCC n-hexylcarborane is blended with a polybutadiene (PBD)/polyurethane (PU) segmented copolymer (EN8) an increase in the glass transition (Tg) temperature of ...


Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler 2017 Iowa State University

Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler

Nicola Bowler

This work investigates the electrothermal lifetime of a commonly used polyimide wire insulation material, Kapton®, through the use of thermogravimetry (TG) and breakdown voltage testing. From TG, an isoconversional model-free kinetic evaluation was used to obtain a relationship between the activation energies of degradation for Kapton as a function of weight loss. By relating the electrical life theory and the TG theory through the model defined by Toop (IEEE Trans. Dielectr. Electr. Insul. 1971, 6, 2), the electrothermal lifetime of Kapton has been calculated for conditions of 12 and 14.7 kV over a temperature range of 250–400°C ...


Dynamics Of Poly(Methyl Methacrylate)–Montmorillonite Nanocomposites: A Dielectric Study, Weixing Sun, Li Li, Michael R. Kessler, Nicola Bowler 2017 Iowa State University

Dynamics Of Poly(Methyl Methacrylate)–Montmorillonite Nanocomposites: A Dielectric Study, Weixing Sun, Li Li, Michael R. Kessler, Nicola Bowler

Nicola Bowler

The effect of varying amounts of montmorillonite (MMT) filler (in weight ratios of 100/0, 100/5, and 100/10) on the molecular dynamics and polarization of atactic poly(methyl methacrylate) (PMMA) is investigated using broad-band dielectric spectroscopy from 10−2 to 106 Hz and at temperatures from 30 to 140 °C. The experimental data were analyzed with the sum of Havriliak–Negami (HN) functions and a power-law conduction term. The characteristic frequency, activation energies, and dielectric strength of PMMA/MMT nanocomposites were analyzed. As MMT content increases, a Maxwell–Wagner–Sillars (MWS) relaxation emerges in the nanocomposites and the ...


Structure-Force Field Generator For Molecular Dynamics Simulations, Carlos M. Patiño, Lorena Alzate, Alejandro Strachan 2017 Universidad de Los Andes - Colombia

Structure-Force Field Generator For Molecular Dynamics Simulations, Carlos M. Patiño, Lorena Alzate, Alejandro Strachan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Atomistic and molecular simulations have become an important research field due to the progress made in computer performance and the necessity of new and improved materials. Despite this, first principle simulations of large molecules are still not possible because the high computational time and resources required. Other methods, such as molecular dynamics, allow the simplification of calculations by defining energy terms to describe multiple atom interactions without compromising accuracy significantly. A group of these energy terms is called a force field, and each force field has its own descriptions and parameters. The objective of this project was to develop a ...


Molecular Dynamics Modeling And Simulation Of Bitumen Chemical Aging, Farshad Fallah 2017 University of Nebraska - Lincoln

Molecular Dynamics Modeling And Simulation Of Bitumen Chemical Aging, Farshad Fallah

Civil Engineering Theses, Dissertations, and Student Research

Chemical aging of asphalt binder leads to significant changes in its mechanical and rheological properties, resulting in poor pavement behavior and distress. Various laboratory methods have been used to simulate asphalt aging during the service life of the pavement. However, controversy exists regarding the capability of these methods to predict field aging, as various factors interact with the pavement during service and the mechanism behind aging is not fully understood. The two main outcomes of chemical aging are oxidation of asphalt molecules, and change in asphalt SARA (saturate, aromatic, resin, and asphaltene) fractions. Reaction of oxygen with asphalt components forms ...


A Study In The Use Of Elastic Materials In Expandable Containment Units, Andrew J. Eisenman, Joby Anthony III, David Satagaj 2017 Liberty University

A Study In The Use Of Elastic Materials In Expandable Containment Units, Andrew J. Eisenman, Joby Anthony Iii, David Satagaj

Montview Liberty University Journal of Undergraduate Research

The rigidity of materials in conjunction with the aspect of elasticity has been a concern of modern technologies and construction in recent centuries because of the advantages that expandable storage would bring to the fields of containment units with respect to population growth and space exploration. The world population is currently growing at an exponential rate, and as our population grows, the more important it will become to have containment units that can both contain large volumes of material as well as minuscule amounts of material without wasting space. In order accomplish this, we will need a new type of ...


Function And Biodegradation In Soil Of Bioplastic Horticultural Containers Made Of Pla-Biorestm Composites, James Schrader, Kenneth McCabe, William Graves, David Grewell 2017 Iowa State University

Function And Biodegradation In Soil Of Bioplastic Horticultural Containers Made Of Pla-Biorestm Composites, James Schrader, Kenneth Mccabe, William Graves, David Grewell

William R Graves

Container-crops horticultural industries rely almost exclusively on petroleum-based plastic containers for modern production systems. Containers made of these materials fulfill all of the functions required during crop production, and perform better than containers made of clay, peat, and other natural materials, but the source of the plastic materials (fossil carbon), their lack of biodegradability, and their end-of-life disposal (97% end up in landfills) are major obstacles to sustainability. Although function and efficiency are among the most important aspects in determining the best materials for horticultural containers, there is no need for containers to persist in the environment for decades when ...


A Graph-Based Formulation For Computational Characterization Of Bulk Heterojunction Morphology, Olga Wodo, Srikanta Tirthapura, Sumit Chaudhary, Baskar Ganapathysubramanian 2017 Iowa State University

A Graph-Based Formulation For Computational Characterization Of Bulk Heterojunction Morphology, Olga Wodo, Srikanta Tirthapura, Sumit Chaudhary, Baskar Ganapathysubramanian

Srikanta Tirthapura

To improve the efficiency of organic solar cells, it is essential to understand the role of morphology and to tailor fabrication process to get desired morphologies. In this context, a comprehensive set of computational tools to quantify and classify the 2D/3D heterogeneous internal structure of thin films is invaluable. We present a graph-based framework to efficiently compute a broad suite of physically meaningful morphology descriptors. These morphology descriptors are further classified according to the physical subprocesses within OSCs – photon absorption, exciton diffusion, charge separation, and charge transport. This approach is motivated by the equivalence between a discretized 2D/3D ...


The Relationship Between Structural Parameters And Mechanical Properties Of Cactus Spines, Jorge Armando Martinez, Pamela Liz Szeto, Theresa Mae Stewart 2017 California Polytechnic State University, San Luis Obispo

The Relationship Between Structural Parameters And Mechanical Properties Of Cactus Spines, Jorge Armando Martinez, Pamela Liz Szeto, Theresa Mae Stewart

Materials Engineering

Considering an increasing interest in renewable, biodegradable resources that exhibit excellent mechanical properties, 24 species of cactus spines were investigated using three-point bend testing, X-ray diffraction (XRD) for structural parameters, and scanning electron microscopy (SEM) to analyze fracture surfaces. Additionally, a density of about 1.3 g/cm3 was measured for each spine utilizing the displacement method, closely matching existing data from literature. The flexural modulus varied greatly between species, ranging from 1.22 GPa (Echinocactus polycephalus) to 43.58 GPa (Stenocereus thurberi). In addition, flexural strength and strain to failure was also measured for each spine. XRD analysis of ...


Feasibility Of Using 3d Printed Molds For Thermoforming Thermoplastic Composites, Sunil Bhandari 2017 University of Maine

Feasibility Of Using 3d Printed Molds For Thermoforming Thermoplastic Composites, Sunil Bhandari

Electronic Theses and Dissertations

This thesis presents a novel combined experimental and numerical mechanics approach for characterizing 3D printed thermoplastic materials by the fused deposition modeling process for thermoforming thermoplastic composites. The implications of this work are:

  1. a methodology for model-based performance evaluation of 3D printed structural parts, and
  2. an improved design of 3D printed molds for composites manufacturing, which has potential for material innovations and scaled-up applications in additive manufacturing.

The thesis formulates basic criteria for selection of thermoplastic polymer used for the 3D printed mold based on forming temperatures. The thesis creates a lattice and shell finite element model of the 3D ...


Renewable And Abundant Battery Components, Jordan T. Sutton, Daniel San Roman, Austin Thomas, Daniel Kitsmiller, Alec Affolter 2017 University of Tennessee, Knoxville

Renewable And Abundant Battery Components, Jordan T. Sutton, Daniel San Roman, Austin Thomas, Daniel Kitsmiller, Alec Affolter

University of Tennessee Honors Thesis Projects

No abstract provided.


Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles 2017 University of Southern Mississippi

Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles

Dissertations

Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of ...


An Investigation Of The Use Of Cerium And Polyhedral Oligomeric Silsesquioxanes For The Protection Of Polymeric Epoxy Compounds In The Low Earth Orbit Environment, Jessica Miriam Piness 2017 University of Southern Mississippi

An Investigation Of The Use Of Cerium And Polyhedral Oligomeric Silsesquioxanes For The Protection Of Polymeric Epoxy Compounds In The Low Earth Orbit Environment, Jessica Miriam Piness

Dissertations

Low Earth orbit presents many hazards for composites including atomic oxygen, UV radiation, thermal cycling, micrometeoroids, and high energy protons. Atomic oxygen and vacuum ultraviolet radiation are of concern for space-bound polymeric materials as they degrade the polymers used as matrices for carbon fiber composites, which are used in satellites and space vehicles due to their high strength to weight ratios. Epoxy-amine thermosets comprise a common class of matrix due to processability and good thermal attributes. Polyhedral oligomeric silsesquioxanes (POSS) have shown the ability to reduce erosion in polyimides, polyurethanes, and other polymers when exposed to atomic oxygen. The POSS ...


Modulation Of Cell Behaviors On Photo-Crosslinked Polymer Networks And Polymer Spherulites, Jinbo Dou 2017 University of Tennessee, Knoxville

Modulation Of Cell Behaviors On Photo-Crosslinked Polymer Networks And Polymer Spherulites, Jinbo Dou

Doctoral Dissertations

This dissertation presents novel biodegradable and photo-crosslinkable poly(-caprolactone) acrylates (PCLAs) to achieve polymer networks with controllable surface chemistry, stiffness, and topographical features, as well as crystallization-induced PCL, poly(3-hydroxybutyrate) (PHB) and poly(L-lactic acid) (PLLA) surfaces for investigating cell-material interactions. Chapter I reviews the recent progress of injectable polymeric biomaterials in the last decade for various tissue engineering applications. Chapter II investigates the variation of thermal and mechanical properties of PCL triacrylate (PCLTA) networks with different crosslinking time, and further studies the smooth muscle cell (SMC) responses to these networks. Chapter III studies the SMC responses to hydrolyzed PCLTA ...


End-Capping Star-Like Polycaprolactone With Different Functional Groups And The Interaction With Smooth Muscle Cells, Qingya Zeng 2017 University of Tennessee, Knoxville

End-Capping Star-Like Polycaprolactone With Different Functional Groups And The Interaction With Smooth Muscle Cells, Qingya Zeng

Masters Theses

Polycaprolactone (PCL) is a PDA-approved biodegradable polymer with excellent biocompatibility and flexibility. My work has been designed to find out how different functional end groups in star-like PCL samples affect the surface properties (such as hydrophilicity, morphology) and bulk properties (such as thermal, mechanical, rheological properties, and crystallization), and consequently the behavior and functions of primary rat aortic smooth muscle cells (SMCs).

I focused on the synthesis of PCL with different functional groups and their characterizations. In chapter 2, PCL samples with four or six hydroxyl end groups were synthesized with different molecular weights ranging from 8,000 to 30 ...


Negahban Group Report: Saw-Tooth Shear Response Of Aged Poly(Methyl Methacrylate) (Pmma), Mehrdad Negahban 2017 University of Nebraska - Lincoln

Negahban Group Report: Saw-Tooth Shear Response Of Aged Poly(Methyl Methacrylate) (Pmma), Mehrdad Negahban

Mechanical & Materials Engineering Faculty Publications

Results for isothermal saw-tooth shear loading experiments conducted on annealed and oven-cooled poly(methyl methacrylate) (PMMA) at temperatures between 50oC and 140oC. The experiments were conducted 1996.


High Capacity Easy Release Extended Use Adhesive Devices, Michael D. Bartlett, Alfred J. Crosby, Andrew B. Croll, Daniel J. King 2017 University of Massachusetts - Amherst

High Capacity Easy Release Extended Use Adhesive Devices, Michael D. Bartlett, Alfred J. Crosby, Andrew B. Croll, Daniel J. King

Michael Bartlett

The invention provides novel devices, systems, designs, materials and fabrication methods that enable high-load capacity, easy release, and suitable for extended/repeated use in a variety of applications.


Dual Mechanism For Toughening And Sustained Aminoglycoside Elution From A Polyphosphate Hydrogel, Dwight D. Lane, Russell J. Stewart PhD 2017 University of Utah

Dual Mechanism For Toughening And Sustained Aminoglycoside Elution From A Polyphosphate Hydrogel, Dwight D. Lane, Russell J. Stewart Phd

Biomedical Engineering Western Regional Conference

No abstract provided.


Effect Of Liquid Contamination On Hermeticity And Seal Strength Of Flexible Pouches With Lldpe, Francesca Delle Cese, Koushik Saha, S. Roy, Jay Singh 2017 California Polytechnic State University

Effect Of Liquid Contamination On Hermeticity And Seal Strength Of Flexible Pouches With Lldpe, Francesca Delle Cese, Koushik Saha, S. Roy, Jay Singh

Journal of Applied Packaging Research

Flexible packaging is a growing successful market and the majority of flexible package applications are for the food industry. The demand for process optimization and reduced production costs, has led to an increase in flexible packaging. However, fast production lines can result in contamination in the seal area. For flexible food packaging, contamination is considered any food particle or substance trapped in the seal area. Current quality control processes can detect contamination in the seal area, but it is not determined if seal contamination affects seal quality. Oil-based and sodium based snack foods are two common categories that can be ...


New Synthetic Platforms For Functional Polymer Zwitterions And Degradable Materials, ChiaChih Chang 2017 University of Massachusetts Amherst

New Synthetic Platforms For Functional Polymer Zwitterions And Degradable Materials, Chiachih Chang

Doctoral Dissertations May 2014 - current

This thesis describes new synthetic platforms for a series of functional polymeric materials containing hydrophilic and/or zwitterionic moieties as pendent groups. The hydrophilicity, biocompatibility, and degradability of these polymers hinged on innovative monomer designs and adaption of appropriate polymerization strategies including controlled radical polymerization, metathesis polymerization, and ring-opening polymerization. Novel, functional sulfobetaine polymers having functional groups (i.e, alkenes and alkynes) directly attached to the zwitterionic moieties were prepared and shown to stabilize oil-water interfaces, allowing for interfacial crosslinking to afford robust polymer capsules. This represents the first example of inserting functionality directly into the zwitterionic moieties of polymer ...


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