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793 full-text articles. Page 1 of 31.

Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler 2018 Iowa State University

Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler

Xiaoli Tan

A three-phase theoretical model is proposed that is suitable for describing the effective permittivity of polymer-matrix composites containing spherical nanoparticles. The model accounts for the presence of an interphase region, which surrounds each nanosphere, whose permittivity is allowed to be different from that of the matrix polymer. The nanoparticles themselves are approximated as hard (non-overlapping) spheres, whereas the interphase regions of neighboring nanoparticles are permitted to overlap. The volume fraction of the interphase region is computed by assuming that the nanoparticles are arranged on the nodes of a simple-cubic lattice. The effective permittivity of the composite is subsequently computed via ...


Depolymerization Of Post-Consumer Polylactic Acid Products, David A. Grewell, Gowrishankar Srinivasan, Eric W. Cochran 2018 Iowa State University

Depolymerization Of Post-Consumer Polylactic Acid Products, David A. Grewell, Gowrishankar Srinivasan, Eric W. Cochran

Eric W. Cochran

Presented in this study is a novel recycling strategy for poly(lactic acid) (PLA) in which the depolymerization is rapidly promoted by the base–catalyzed hydrol–/alcohol–ysis of the terminal ester bonds under mild conditions. Post–consumer PLA water bottles were cut into approximately 6 × 2 mm plastic chips and heated to 50–60×C in water, ethanol, or methanol as the depolymerization medium. A variety of carbonate salts and alkaline metal oxides were screened as potential catalysts. High–power ultrasound was also investigated as a means to accelerate the PLA decomposition. Both mass loss and HPLC analysis of ...


Synthesis And Functionalization Of Virus-Mimicking Cationic Block Copolymers With Pathogen-Associated Carbohydrates As Potential Vaccine Adjuvants, J. R. Adams, M. Goswami, N. L.B. Pohl, Surya K. Mallapragada 2018 Iowa State University

Synthesis And Functionalization Of Virus-Mimicking Cationic Block Copolymers With Pathogen-Associated Carbohydrates As Potential Vaccine Adjuvants, J. R. Adams, M. Goswami, N. L.B. Pohl, Surya K. Mallapragada

Surya K. Mallapragada

We report the synthesis of a family of amphiphilic pentablock polymers with different cationic blocks and with controlled architectures as potential vaccine carriers for subunit vaccines. The temperature and pH-dependent micellization and gelation of these pentablock copolymers can provide a depot for sustained protein and gene delivery. The amphiphilic central triblock promotes cellular endocytosis, good gene delivery and has been used effectively as a vaccine adjuvant. The pentablock copolymer outer blocks condense DNA spontaneously as a result of electrostatic interactions for sustained combinational therapy. This family of polymers with different cationic groups was evaluated based on DNA complexation-ability and cytotoxicity ...


Protein Patterns Template Arrays Of Magnetic Nanoparticles, Srikanth Nayak, Honghu Zhang, Xunpei Liu, Shuren Feng, Pierre Palo, Marit Nilsen-Hamilton, Mufit Akinc, Surya K. Mallapragada 2018 Iowa State University and Ames Laboratory

Protein Patterns Template Arrays Of Magnetic Nanoparticles, Srikanth Nayak, Honghu Zhang, Xunpei Liu, Shuren Feng, Pierre Palo, Marit Nilsen-Hamilton, Mufit Akinc, Surya K. Mallapragada

Surya K. Mallapragada

Controlling the morphology of magnetic nanoparticles and their spatial arrangement is crucial for manipulating their functional properties. The commonly available inorganic processes for the synthesis of uniform magnetic nanoparticles typically require extreme reaction conditions such as high temperatures or harsh reagents, rendering them unsuitable for making functionalized magnetic nanoparticles with tunable properties controlled by biomolecules. Biomimetic procedures, inspired by the production of uniform magnetite and greigite crystals in magnetotactic bacteria, provide an alternative method, which can allow synthesis and spatial arrangement under ambient conditions. Mms6, an amphiphilic protein found in magnetosome membranes in Magnetospirillum magneticum strain AMB-1, can control the ...


Surface Engineering And Monomer Design For Light-Mediated Ring Opening Metathesis Polymerization, Ishan A. Fursule 2018 University of Kentucky

Surface Engineering And Monomer Design For Light-Mediated Ring Opening Metathesis Polymerization, Ishan A. Fursule

Theses and Dissertations--Chemical and Materials Engineering

Stimuli-responsive materials are changing the landscape of actuated materials, optoelectronics, molecular machines, solar cells, temporary memory storage, and biomedical materials. Specifically, photo-responsive polymers have gained acceleration in research and application since the last two decades in the form of a surface coating and micro-patterns. Light as a stimulus can be coherent, mono or polychromatic, tunable for power (intensity) and energy (wavelength), and has precise spatiotemporal control. Conventional surface coating techniques such as spin coating are unable to impart properties to the coatings in terms of sturdiness, homogeneity, uniformity over the complex surface, post deposition modification, and process efficiency. Also, in ...


Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri 2017 Iowa State University

Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri

Ames Laboratory Accepted Manuscripts

Removing organics from hybrid nanostructures is a crucial step in many bottom-up materials fabrication approaches. It is usually assumed that calcination is an effective solution to this problem, especially for thin films. This assumption has led to its application in thousands of papers. We here show that this general assumption is incorrect by using a relevant and highly controlled model system consisting of thin films of ligand-capped ZrO2 nanocrystals. After calcination at 800 °C for 12 h, while Raman spectroscopy fails to detect the ligands after calcination, elastic backscattering spectrometry characterization demonstrates that ~18% of the original carbon atoms are ...


Usa Boccia Ball Ramp For Athletes With Quadriplegia, Alissa A. Koukourikos, Nathan Bernards, Matthew Lee 2017 Cal Poly State University San Luis Obispo

Usa Boccia Ball Ramp For Athletes With Quadriplegia, Alissa A. Koukourikos, Nathan Bernards, Matthew Lee

Mechanical Engineering

No abstract provided.


Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan 2017 University of Nebraska-Lincoln

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method ...


Influence Of Lignocellulose Fillers On Properties Natural Rubber Composites, Przemyslaw Rybiński, Bartłomiej Syrek, Marcin Masłowski, Justyna Miedzianowska, Krzysztof Strzelec, Witold Zukowski, Dariusz Bradło 2017 Cracow University of Technology

Influence Of Lignocellulose Fillers On Properties Natural Rubber Composites, Przemyslaw Rybiński, Bartłomiej Syrek, Marcin Masłowski, Justyna Miedzianowska, Krzysztof Strzelec, Witold Zukowski, Dariusz Bradło

Witold Zukowski

The present article presents unreported yet in the subject literature examinations of the effect of a lignocellulose filler obtained from an alkalized wheat straw treated with di-potassium phosphate on the properties of natural rubber composites. The thermal and mechanical properties as well as the fire hazard of the composites obtained were tested also in the presence of an additive flame-retardant compound (poly(ammonium phosphate)), exploiting the synergism of its action with pentaerythritol, antimony trioxide, aluminum hydroxide and zinc borate. Based on the results obtained by the methods of thermal and mechanical analyses, micro-calorimetry and cone calorimetry, it has been found ...


Development Of Starch-Polyvinyl Alcohol (Pva) Biodegradable Film: Effect Of Cross-Linking Agent And Antimicrobials On Film Characteristics, Aniket Satish More, Chandani Sen, Madhusweta Das 2017 Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur

Development Of Starch-Polyvinyl Alcohol (Pva) Biodegradable Film: Effect Of Cross-Linking Agent And Antimicrobials On Film Characteristics, Aniket Satish More, Chandani Sen, Madhusweta Das

Journal of Applied Packaging Research

To satisfy the need of developing eco-friendly flexible antimicrobial packaging film with minimum use of synthetic chemical ingredients, the present study examined the efficacy of citric acid (CA) as cross-linking agent and essential oils (EOs), viz., cinnamon essential oil (CEO) and oregano essential oil (OEO) as natural antimicrobials in corn starch-polyvinyl alcohol (CS-PVA) film. Compared to film prepared from filmogenic solution (FS) containing 75 kg CS+8.75 kg PVA+24.6 kg glycerol per m3 FS, film additionally containing CA at 0.07 kg/kg CS indicated 95% higher ultimate tensile strength (UTS) and 27% lower water vapor ...


Effects Of Lignin As A Stabilizer Or Antioxidant In Polyolefins, Afsana S. Kabir 2017 The University of Western Ontario

Effects Of Lignin As A Stabilizer Or Antioxidant In Polyolefins, Afsana S. Kabir

Electronic Thesis and Dissertation Repository

Lignin, a major component of biomass, is an attractive alternative to hindered phenol-based antioxidants for polymers due to its renewable nature and naturally occurring hindered phenolic structure. In this study, for the first time, lignin de-polymerization was explored as a promising approach to improve the reactivity of the lignin-based antioxidants for polymers (polyethylene, PE and polypropylene, PP). A proprietary hydrolytic de-polymerization process was utilized to increase the antioxidant activity of two types of technical lignin: kraft lignin, KL (a by-product from the pulp and paper industry) and hydrolysis lignin, HL (a by-product from the pre-treatment processes in cellulosic ethanol plants ...


Additive Manufacturing Process Of 3d Polyaniline Transducers Via Direct Ink Writing, Frederick Benjamin Holness 2017 The University of Western Ontario

Additive Manufacturing Process Of 3d Polyaniline Transducers Via Direct Ink Writing, Frederick Benjamin Holness

Electronic Thesis and Dissertation Repository

Electroactive polymers exhibit a change in properties, typically size or shape, in response to electrical stimuli. One class of electroactive polymer of particular interest are the conjugated polymers, whose conjugated backbone structure imparts electrical conductivity. However, this structure imposes processing limitations restricting their form to 2D structures. To overcome this, we develop specially formulated polyaniline- based blends via counter-ion induced thermal doping for the fabrication of 3D conductive structures via direct ink writing. This approach employs multi-material extrusion for the production of structures with passive and active features, rapid device fabrication, and improved design freedom. A model of the thermal ...


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 ...


Usage Of Fomblin Y To Improve Water Repellence Of Surface Coatings, Shawn PJ Kirby, Jeffrey Alston, Andrew Guenthner 2017 California State University - Long Beach

Usage Of Fomblin Y To Improve Water Repellence Of Surface Coatings, Shawn Pj Kirby, Jeffrey Alston, Andrew Guenthner

STAR (STEM Teacher and Researcher) Presentations

Fluoro-Decyl POSS (FDP) has shown strong potential as a water repellant surface coating. Additionally, Fomblin is a solvent believed to have the ability to control the crystallization of POSS compounds on surfaces. Controlling the crystallization is key to improving water repelling abilities of surfaces. Thus, dip coating FDP and Fomblin onto surfaces is being investigated for water repulsion, mechanical stability, and deposition feasibility. Relative water repelling abilities of different coatings were determined by measuring contact angle of surfaces with water. Coatings with and without POSS and Fomblin were compared. It was shown that the surfaces treated with both POSS and ...


Cellulose Reinforced Thermoplastic Composites By In-Situ Ring-Opening Polymerization, Shahab Kashani Rahimi 2017 University of Southern Mississippi

Cellulose Reinforced Thermoplastic Composites By In-Situ Ring-Opening Polymerization, Shahab Kashani Rahimi

Dissertations

Over the past two decades, the increasing concern about the negative environmental impacts of synthetic materials has led to rising interests in utilizing renewable natural resources to develop polymer materials with comparable properties and performance to their synthetic counterparts. One of the major fields of interest is polymer composites where the replacement of synthetic fibers with bio renewable natural fibers is of great potential. However, the processing difficulties, in terms of fiber dispersion and thermal stability have limited the application of cellulosic fibers to polymers with low processing temperatures which are mostly hydrophobic polymers. As a result, the true reinforcing ...


Membranes For Food And Bioproduct Processing, Alexandru Marius Avram 2017 University of Arkansas, Fayetteville

Membranes For Food And Bioproduct Processing, Alexandru Marius Avram

Theses and Dissertations

Modified membranes for process intensification in biomass hydrolysis

Production of biofuels and chemicals from lignocellulosic biomass is one of the leading candidates for replacement of petroleum based fuels and chemicals. However, conversion of lignocellulosic biomass into fuels and chemicals is not cost effective compared to the production of fuels and chemicals from crude oil reserves. Some novel and economically feasible approaches involve the use of ionic liquids as solvents or co-solvents, since these show improved solvation capability of cellulose over simple aqueous systems. Membranes offer unique opportunities for process intensification which involves fractionation of the resulting biomass hydrolysate leading to ...


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 ...


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