Mass spectrometric analyses of high performance polymers to assess their radiopurity as ultra low background materials for rare event physics detectors
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Grate, Jay W. (ORCID:0000000221638383)↗
SEARCH · Engineering Papers
Results for “polymer mechanics”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Nanoscale Miscibility in In Situ Polymerized Hybrid Electrolytes Speeds Up Ion Dynamics and Enables Stable Cycling of Li Metal Batteries
While the potential use of copolymerized electrolytes in Li metal batteries is subject to intense investigation, the fundamental understanding of the nanoscale domain formation and its effect on Li + transport is still lacking. In this study, we investigated the correlation between the Li + transport mechanism and the miscibility of monomers in polymer blend electrolytes derived from the in situ copolymerization of methyl methacrylate (MMA) and vinylene carbonate (VC) in the presence of polyethylene glycol dimethyl ether (PEGDME) plasticizer and bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The addition of a polar short chain plasticizer reduced the dynamic and structural heterogeneities of the electrolyte. Small-angle X-ray scattering (SAXS) measurements and coarse-grained molecular dynamics (MD) simulations were used to investigate the nanoscale structure of the electrolytes. The distribution of relaxation times corresponding to the three distinct diffusion mechanisms of the free and interfacial Li + ions at the copolymer/plasticizer and electrolyte/SEI boundaries was analyzed in a broad temperature range to elucidate the Li + transport mechanism. Furthermore, the chemical composition of the SEI and the contribution of a ceramic lithium lanthanum zirconium oxide (LLZO, Li 7 La 3 Zr 2 O 12 ) phase on the interfacial resistance, salt degradation, and SEI stability were studied by X-ray photoelectron spectroscopy (XPS) depth profile analysis and electrochemical testing.
Li metal↗
Ion Transport in Batteries with Polymer Electrolytes
We discuss polymer electrolytes for use in rechargeable lithium batteries. Polymer electrolytes have the potential to enable batteries with lithium metal anodes. These batteries have significantly higher theoretical energy densities than current lithium-ion batteries. We consider binary mixtures of polymers and salts. We also cover more complex systems such as polymer electrolytes swollen with a solvent (gel polymer electrolytes) and microphase separated polymer electrolytes. By covalently attaching the anions to the chains in a polymer solid, one obtains a single-ion conductor. We mainly focus on experiments wherein the polymer electrolyte is placed between two lithium metal electrodes. These experiments enable the determination of three transport parameters, ionic conductivity, salt diffusion coefficient, and transference number, and the thermodynamic factor. The properties of dry polymer electrolytes are contrasted with those of gel polymer electrolytes. The gel systems exhibit higher conductivity while the dry systems exhibit superior mechanical properties. We discuss interfacial impedance when lithium metal is contacted with polymer electrolytes and the importance of coulombic efficiency.
Yu, Xiaopeng↗
Polymeric membrane systems of potential use for battery separators
Two membrane systems were investigated that may have potential use as alkaline battery separators. One system comprises two miscible polymers: a support polymer (e.g., polyvinyl formal) and an ion conductor such as polyacrylic acid. The other system involves a film composed of two immiscible polymers: a conducting polymer (e.g., calcium polyacrylate) suspended in an inert polymer support matrix, polyphenylene oxide. Resistivities in 45-percent potassium hydroxide and qualitative mechanical properties are presented for films comprising various proportions of conducting and support polymers. In terms of these parameters, the results are encouraging for optimum ratios of conducting to support polymers.
Philipp, W. H.↗
Enabling novel space and terrestrial applications using transducing materials at JPL
Transducing materials are being used in many aspects of our daily life serving as actuators, sensors, displays, communications and other components of commercial mechanisms. At JPL, such materials are being used to enable novel space and terrestrial applications. This effort involves mostly the use of piezoelectric, electroactive polymers (EAP), and shape memory alloys (SMA). The piezoelectric based devices and mechanisms that were developed include ultrasonic motors, piezopump, ultrasonic/sonic drilledcorer (USDC), and ferrosource. Further, the electroactive polymers were used to demonstrate a gripper, wiper, lifter and haptic interfaces. The research and develop tasks consists of analytical modeling, experimental corroboration, material characterization as well as devices and mechanisms design, construction and demonstration.
electroactive↗
Advanced Electron Microscopy of Nanophased Synthetic Polymers and Soft Complexes for Energy and Medicine Applications
After decades of developments, electron microscopy has become a powerful and irreplaceable tool in understanding the ionic, electrical, mechanical, chemical, and other functional performances of next-generation polymers and soft complexes. The recent progress in electron microscopy of nanostructured polymers and soft assemblies is important for applications in many different fields, including, but not limited to, mesoporous and nanoporous materials, absorbents, membranes, solid electrolytes, battery electrodes, ion- and electron-transporting materials, organic semiconductors, soft robotics, optoelectronic devices, biomass, soft magnetic materials, and pharmaceutical drug design. For synthetic polymers and soft complexes, there are four main characteristics that differentiate them from their inorganic or biomacromolecular counterparts in electron microscopy studies: (1) lower contrast, (2) abundance of light elements, (3) polydispersity or nanomorphological variations, and (4) large changes induced by electron beams. Since 2011, the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory has been working with numerous facility users on nanostructured polymer composites, block copolymers, polymer brushes, conjugated molecules, organic–inorganic hybrid nanomaterials, organic–inorganic interfaces, organic crystals, and other soft complexes. This review crystalizes some of the essential challenges, successes, failures, and techniques during the process in the past ten years. It also presents some outlooks and future expectations on the basis of these works at the intersection of electron microscopy, soft matter, and artificial intelligence. Machine learning is expected to automate and facilitate image processing and information extraction of polymer and soft hybrid nanostructures in aspects such as dose-controlled imaging and structure analysis.
36 MATERIALS SCIENCE↗
Ionic Polyimides: New High Performance Polymers for Additive Manufacturing
There is currently a very limited set of engineering polymers that have been demonstrated as viable for use in 3-D printing. Additive manufacturing of custom components will require a much larger array of polymers, especially those with physical, thermal, chemical, and mechanical properties that can be tailor-made. The development of ‘Ionic Polyimides’ offers a solution to this shortage by combining the well understood and widely accepted properties of conventional polyimides, with a new approach to polymer synthesis. Polyimides and polymeric ionic liquids (poly(ILs)) are at the forefront of advanced polymer materials, each with their own set of advantages and disadvantages. While it is clear that more types of polymer materials are needed for fused deposition modeling (FDM) additive manufacturing, there is a need to explore these classes of materials. The synthesis process developed by the Bara Research Group at the University of Alabama allows full control over polymer structure, nanostructure, thermal, electrical, and physical properties making them a prime candidate for use in the additive manufacturing process. Furthermore, the new process allows us to tailor-make a high strength polymer that can be used to fabricate filament feedstock instead of pellets for 3D printing. The primary objective of this proposal is to determine the relationship between molecular structure, physical properties, and performance of ionic polyimides. Further, we seek to determine their utility as materials suitable for additive manufacturing of components used in aerospace vehicles, with an emphasis on characterizing and simulating their thermal behaviors and properties. This proposal addresses the need for fundamental research on a customizable polymer filament feedstock for 3-D printing with tailor-made properties potentially making it superior to the commercial blends offered in industry today. The deliverables for this project are the creation of a database that will detail the relationships between the molecular structure and physical properties for the ionic polyimide of interest (e.g. Tg/Tm (Glass Transition Temperature divided by Melting Point)) relative to different ionic polyimide structures). This new database will provide a “road map” to the development of the first generation of materials and ultimately proof-of-concept.
Jackson, Enrique↗
Ionic Polyimides: New High Performance Polymers for Additive Manufacturing
There is currently a very limited set of engineering polymers that have been demonstrated as viable for use in 3-D printing. Additive manufacturing of custom components will require a much larger array of polymers, especially those with physical, thermal, chemical, and mechanical properties that can be tailor-made. The development of ‘Ionic Polyimides’ offers a solution to this shortage by combining the well understood and widely accepted properties of conventional polyimides, with a new approach to polymer synthesis. Polyimides and polymeric ionic liquids (poly(ILs)) are at the forefront of advanced polymer materials, each with their own set of advantages and disadvantages. While it is clear that more types of polymer materials are needed for fused deposition modeling (FDM) additive manufacturing, there is a need to explore these classes of materials. The synthesis process developed by the Bara Research Group at the University of Alabama allows full control over polymer structure, nanostructure, thermal, electrical, and physical properties making them a prime candidate for use in the additive manufacturing process.
Jackson, Enrique↗
Bioinspired mechanical mineralization of organogels
Mineralization is a long-lasting method commonly used by biological materials to selectively strengthen in response to site specific mechanical stress. Achieving a similar form of toughening in synthetic polymer composites remains challenging. In previous work, we developed methods to promote chemical reactions via the piezoelectrochemical effect with mechanical responses of inorganic, ZnO nanoparticles. Herein, we report a distinct example of a mechanically-mediated reaction in which the spherical ZnO nanoparticles react themselves leading to the formation of microrods composed of a Zn/S mineral inside an organogel. The microrods can be used to selectively create mineral deposits within the material resulting in the strengthening of the overall resulting composite.
59 BASIC BIOLOGICAL SCIENCES↗
NMR (Nuclear Magnetic Resonance) and macromolecular migration in a melt or in concentrated solutions
The purpose of this paper is to analyze the migration process of long polymer molecules in a melt or in concentrated solutions as it may be observed from the dynamics of the transverse magnetization of nuclear spins linked to these chains. The low frequency viscoelastic relaxation of polymer systems is known to be mainly controlled by the mechanism of dissociation of topological constraints excited on chains and which are called entanglements. This mechanism exhibits a strong dependence upon the chain molecular weight. These topological constraints also govern the diffusion process of polymer chains. So, the accurate description of the diffusion motion of a chain may be a convenient way to characterize disentanglement processes necessarily involved in any model proposed to explain viscoelastic effects.
Addad, J. P. C.↗
Mechanism of the Comonomer Effect in LLDPE from Ethylene/1-Hexene Using a Quinoline-Amine Hafnium Catalyst
Polymers of ethylene and copolymers of ethylene and 1-hexene are synthesized by utilizing a single-site hafnium catalyst activated with tris(pentafluorophenyl)borane. Polymer production increases sharply as compared to the homopolymerization of ethylene with the addition of just a small amount of 1-hexene-a phenomenon known as the "comonomer effect." A mechanism behind the comonomer effect is proposed where the activation-initiation step plays the key part. When only a small fraction of the precatalyst is initially active, high molecular weight (170 000 g mol -1 , Đ 1.6) polymer chains grow, forming a physical gel structure that traps catalyst, monomer, and solvent molecules, thereby shutting down the reaction-this scenario plays out in the case of homopolymerization of ethylene. 1-Hexene, when present, slows down the chain growth, thereby lowering the molecular weight and preventing the formation of a gel, which in turn allows for more catalytic sites to be initiated; the reaction continues, resulting in a larger amount of polymer of lower molecular weight (25 000 g mol -1 ). The proposed mechanism is validated in a series of experiments where targeted variation of the activation/initiation steps is shown to produce, depending on the condition, either a small amount of high molecular weight physical gel or a large amount of low molecular weight polymer.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Biologically Inspired Technology Using Electroactive Polymers (EAP)
Evolution allowed nature to introduce highly effective biological mechanisms that are incredible inspiration for innovation. Humans have always made efforts to imitate nature's inventions and we are increasingly making advances that it becomes significantly easier to imitate, copy, and adapt biological methods, processes and systems. This brought us to the ability to create technology that is far beyond the simple mimicking of nature. Having better tools to understand and to implement nature's principles we are now equipped like never before to be inspired by nature and to employ our tools in far superior ways. Effectively, by bio-inspiration we can have a better view and value of nature capability while studying its models to learn what can be extracted, copied or adapted. Using electroactive polymers (EAP) as artificial muscles is adding an important element to the development of biologically inspired technologies.
robotics↗
Multi-Scale CNT-Based Reinforcing Polymer Matrix Composites for Lightweight Structures
Reinforcing critical areas in carbon polymer matrix composites (PMCs), also known as fiber reinforced composites (FRCs), is advantageous for structural durability. Since carbon nanotubes (CNTs) have extremely high tensile strength, they can be used as a functional additive to enhance the mechanical properties of FRCs. However, CNTs are not readily dispersible in the polymer matrix, which leads to lower than theoretically predicted improvement in mechanical, thermal, and electrical properties of CNT composites. The inability to align CNTs in a polymer matrix is also a known issue. The feasibility of incorporating aligned CNTs into an FRC was demonstrated using a novel, yet commercially viable nanofiber approach, termed NRMs (nanofiber-reinforcing mats). The NRM concept of reinforcement allows for a convenient and safe means of incorporating CNTs into FRC structural components specifically where they are needed during the fabrication process. NRMs, fabricated through a novel and scalable process, were incorporated into FRC test panels using layup and vacuum bagging techniques, where alternating layers of the NRM and carbon prepreg were used to form the reinforced FRC structure. Control FRC test panel coupons were also fabricated in the same manner, but comprised of only carbon prepreg. The FRC coupons were machined to size and tested for flexural, tensile, and compression properties. This effort demonstrated that FRC structures can be fabricated using the NRM concept, with an increased average load at break during flexural testing versus that of the control. The NASA applications for the developed technologies are for lightweight structures for in-space and launch vehicles. In addition, the developed technologies would find use in NASA aerospace applications such as rockets, aircraft, aircraft/spacecraft propulsion systems, and supporting facilities. The reinforcing aspect of the technology will allow for more efficient joining of fiber composite parts, thus offering additional weight savings. More robust structures capable of withstanding micrometeoroid and space debris impacts will be possible with the enhanced mechanical properties imparted by the aligned CNTs incorporated into the fiber composite structure, as well as the potential for improved electrical and thermal properties. The materials fabrication approach developed in the present effort is a platform for customer applications where additional reinforcement is required or would be beneficial, especially in FRC structures and component parts. Depending upon the specific customer application, the NRM could be tailored to the specific matrix resin and desired property enhancement.
Eberly, Daniel↗
Intrinsic thermal interfacial resistance measurement in bonded metal–polymer foils
Heat conduction through bonded metal–polymer interfaces often limits the overall heat transfer in electronic packaging, batteries, and heat recovery systems. To design the thermal circuit in such systems, it is essential to measure the thermal interfacial resistance (TIR) across ~1 µm to 100 µm junctions. Previously reported TIR of metal–polymer junctions utilize ASTM E1530-based two-block systems that measure the TIR by applying pressure across the interface through external heating and cooling blocks. Here, we report a novel modification of the ASTM-E1530 technique that employs integrated heaters and sensors to provide an intrinsic TIR measurement of an adhesively bonded metal–polymer junction. We design the measurement technique using finite element simulations to either passively suppress or actively compensate the lateral heat diffusion through the polymer, which can minimize the systematic error to ≲5%. Through proof-of-concept experiments, we report the TIR of metal–polymer interfaces made from DuPont’s Pyralux double-side copper-clad laminates, commonly used in flexible printed circuit boards. Our TIR measurement errors are <10%. We highlight additional sources of errors due to non-idealities in the experiment and discuss possible ways to overcome them. Our measurement technique is also applicable to interfaces that are electrically insulating such as adhesively joined metal–metal junctions and sputter-coated or welded metal–polymer junctions. Altogether, the technique is capable of measuring TIR ≳10 –5 m 2 KW –1 in bonded metal–polymer foils and can be tailored for in situ measurements in flexible electronics, circuit packaging, and other hybrid metal–polymer systems.
47 OTHER INSTRUMENTATION↗
A Novel Manufacturing Process of Lightweight Automotive Seats (Integration of Additive Manufacturing and Reinforced Polymer Composite)
Lightweight automotive seats offer multiple benefits to original equipment manufacturers in terms of cost savings from various aspects, including less material usage, more integrated processes, and compliance with Corporate Average Fuel Economy Standards. Original equipment manufacturers have been focusing on innovative ways to produce light weight automotive seats. The commercially available automotive seats are currently made of multiple metal components combined through welding and fasteners. The use of additive manufacturing and composite structures is particularly useful for light weighting the automotive components. Additive manufacturing (AM) offers multiple advantages over traditional manufacturing processes such as freedom of design thereby enabling complex structural geometries, mass customization and waste minimization, and control over the fiber alignment through deposition in a predetermined pattern. Combining metal inserts with polymer composites through a novel manufacturing process allows design of lightweight and high-performance materials for automotive components. However, fabricating these metal polymer composite structures through traditional manufacturing processes limits their mechanical properties due to limited design freedom, lack of control over fiber orientation in composite parts, and poor interfacial bonding between the constituent materials. It is essential to develop a novel manufacturing process to enable high throughput production of lightweight automotive seats using metal and polymer composites. As such it is important to design the automotive seat suitable for manufacturing via this process and perform mechanical characterization on various subcomponents of the seat to ensure that the design and performance requirements provided by the auto manufacturer are met. The aim of this project is to develop a novel manufacturing technique to produce lightweight automotive seat by combining AM with conventional manufacturing processes. The car seat back panel will be designed via topology optimization and numerical simulations to minimize the overall weight while ensuring it meets all the performance requirements. The optimization of the seat back structure will be based on computational stress analysis to maximize the stiffness and minimize the weight. Materials currently used by Ford Motor Company will be adopted for a few subcomponents while the in-house composite materials will be used for the rest of the seat back. The composite and metallic materials will be tested to determine their mechanical properties as these are necessary for simulations. A novel manufacturing process will be developed to integrate AM metal inserts with discontinuous reinforced composite through large scale additive manufacturing and compression overmolding processes. The developed manufacturing technique will be used to fabricated various subcomponents suitable for the seat back design and mechanically tested to determine their properties. The manufacturing of the lightweight seat back design through this process involves integrated AM metal inserts with the composite structure for recliner connection. The manufacturing of the entire seat back which is lightweight through the novel manufacturing process will be discussed. The performance of the designed seat back will be investigated through numerical simulations and shown to meet all the requirements provided by the auto manufacturer. The final goal of developing a novel manufacturing process for lightweight automotive seats is met through design optimization of seat back, manufacturing of subcomponents, mechanical characterization, and validation through numerical simulations. The routes to achieve the final goal of the project and the depth in which they were investigated changed throughout the project due to personnel changes and the COVID-19 pandemic. The project resulted in the development of a novel manufacturing process to integrate metal inserts with tailored polymer composite preforms through overmolding. Leveraging this proven manufacturing process, a lightweight seat back was designed through topology optimization and numerical simulations. The designed seat back uses AM metal inserts and compression overmolding of tailored polymer composite preforms obtained via large scale additive manufacturing. The metal polymer composite structures fabricated through this process exhibited enhancement in stiffness and improved ductility upon testing. Overall, the project provided an alternative design and manufacturing technique for automotive seat back that enables weight saving while meeting the safety and performance requirements.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Effects of gamma, electron beam, and X-ray irradiation on the plastic components of a universal bone cement mixer medical device
Due to market and regulatory pressures, many healthcare manufacturers are considering alternatives to cobalt-60 gamma radiation, including accelerator-based electron beam (E-beam) and X-ray radiation for product sterilization. In this work, the effects of irradiation on a representative medical product, comprised of eight distinct polymer materials, were directly compared for three radiation technologies – cobalt-60 gamma, E-beam, and X-ray – at four dose levels (15, 25, 50, and 70 kGy). The objective was to determine how radiation effects (deleterious or beneficial) are influenced by source and dose level, with the specific goal of determining whether E-beam radiation and/or X-ray radiation could be viable alternatives to gamma radiation for device sterilization. Here, the specific product considered is a single-use medical device for orthopedic surgery, the Stryker Instruments MixeVac III bone cement mixer, which is currently sterilized using gamma radiation from cobalt-60 sources. Following ASTM International standards and input from the manufacturer, we characterized the effects of the three radiation sources on product functionality as well as on the mechanical and optical properties of the constituent polymers. Results indicate that although measurable differences in properties between the standard gamma irradiated materials and the alternative E-beam and X-ray irradiated materials were observed, those differences were small. Statistically significant differences were noted in the case of yellowness index for polyvinyl chloride, high-density polyethylene, and polycarbonate, and in the case of tensile elongation at break for high impact polystyrene and polyvinyl chloride. In general, the results of this study support the viability of E-beam and X-ray radiation as alternative options to cobalt-60 gamma radiation for sterilization of Stryker single-use universal bone cement mixer medical devices.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
New Method Developed To Purify Single Wall Carbon Nanotubes for Aerospace Applications
Single wall carbon nanotubes have attracted considerable attention because of their remarkable mechanical properties and electrical and thermal conductivities. Use of these materials as primary or secondary reinforcements in polymers or ceramics could lead to new materials with significantly enhanced mechanical strength and electrical and thermal conductivity. Use of carbon-nanotube-reinforced materials in aerospace components will enable substantial reductions in component weight and improvements in durability and safety. Potential applications for single wall carbon nanotubes include lightweight components for vehicle structures and propulsion systems, fuel cell components (bipolar plates and electrodes) and battery electrodes, and ultra-lightweight materials for use in solar sails. A major barrier to the successful use of carbon nanotubes in these components is the need for methods to economically produce pure carbon nanotubes in large enough quantities to not only evaluate their suitability for certain applications but also produce actual components. Most carbon nanotube synthesis methods, including the HiPCO (high pressure carbon monoxide) method developed by Smalley and others, employ metal catalysts that remain trapped in the final product. These catalyst impurities can affect nanotube properties and accelerate their decomposition. The development of techniques to remove most, if not all, of these impurities is essential to their successful use in practical applications. A new method has been developed at the NASA Glenn Research Center to purify gram-scale quantities of single wall carbon nanotubes. This method, a modification of a gas phase purification technique previously reported by Smalley and others, uses a combination of high-temperature oxidations and repeated extractions with nitric and hydrochloric acid. This improved procedure significantly reduces the amount of impurities (catalyst and nonnanotube forms of carbon) within the nanotubes, increasing their stability significantly. The onset of decomposition of the purified nanotubes (determined by thermal gravimetric analysis in air) is more than 300 C higher than that of the crude nanotubes. Transmission electron microscopy analysis of nanotubes purified by this method reveals near complete removal of iron catalyst particles. Analysis of the nanotubes using inductively coupled plasma spectroscopy revealed that the iron content of the nanotubes was reduced from 22.7 wt% in the crude nanotubes to less than 0.02 wt%. X-ray photoelectron spectroscopy revealed a decrease in iron content after purification as well as an increase in oxygen content due to the formation of carboxylic acid groups on the surface of the nanotubes. Nanotubes purified by this improved method can be readily dispersed in common organic solvents, in particular N,N-dimethylformamide, using prolonged ultrasonic treatment. These dispersions can then be used to incorporate single wall carbon nanotubes into polymer films.
Lebron, Marisabel↗
Impact of Grafting Density on the Assembly and Mechanical Properties of Self-Assembled Metal–Organic Framework Monolayers
Polymer-grafted metal–organic frameworks (MOFs) can be used to form free-standing self-assembled MOF monolayers (SAMMs). Polymer chains can be introduced onto MOF surfaces through either the ligands or metal nodes using both grafting-to and grafting-from approaches. However, controlling the grafting density of polymer-grafted MOFs has not yet been achieved, because a means to control the density of grafting sites on the MOF surface has not been developed. In this study, the grafting density of polymer-grafted UiO-66 (UiO = University of Oslo) was controlled by functionalizing a portion of the Zr(IV) secondary building units (SBUs) on a UiO-66 surface with a so-called blocking agent. The remaining sites on the UiO-66 SBUs were functionalized with polymerization initiation groups, and polymers were grown from these sites to obtain particles with variable grafting densities and chain lengths that form SAMMs at an air–water interface. Even under conditions of low grafting density, these materials retain the ability to form SAMMs and their free-standing ability. Changes in particle arrangement within the monolayers were investigated using SEM imaging, and the toughness of the monolayers was evaluated using a film-on-water (FOW) method. Furthermore, coarse-grained molecular dynamics simulations were carried out to elucidate the morphology and mechanical properties of the monolayers. Findings from both experiments and simulations indicate that the toughness of SAMMs is more heavily influenced by the chain length of the grafted polymers than by the overall polymer content in the composite.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗