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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Mechanical Properties of Permanent Foaming Fixatives for Deactivation and Decommissioning Activities

DOE-EM have identified an operational requirement for a fixative that can immobilize and/or encapsulate residual contamination in 3D void volumes (pipes, gloveboxes, waste containers, etc.) during D and D activities. Failure to safely and effectively immobilize residual contamination can: Put workers at risk, Contaminate the public and environment, Drive up operational costs. Commercial-off-the-shelf (COTS) polyurethane (PU) foams is one possible solution and is currently being investigated in collaboration with Savannah River National Lab (SRNL). Mechanical property testing will dictate how well PU foams can withstand physical stressors outlined in safety documents while immobilizing residual contamination. Results can provide a performance criteria for Section 5 of ASTM E3191: Standard Specification for Permanent Foaming Fixatives Used to Mitigate Spread of Radioactive Contamination. Polyurethanes consists of repeating units of urethanes which are produced from an exothermic reaction between a polyol (an alcohol with two or more hydroxyl groups in a molecule) and an isocyanate [2]. PUs consists of 3D cells that are formed by a blowing agent which is normally water. Water interacting with the isocyanate creates carbon dioxide and urea which contributes to cells' growth and expansion. The cross-linking between the polyol and isocyanate solidify the cell faces and walls. Micro scale properties that can influence mechanical properties include: Relative density (ratio between density of cellular material and density of the solid of which the cell walls are made of). Cells connectivity between edges and faces, and number of cells contact neighbors [3]. Whether a foam is open-celled or closed-celled. Closed-celled foams have a thin membrane that encloses each cell which can contribute to the stiffness of the foam. Incorporating fillers in the PU matrix like carbon-based nanoparticles in the form of expandable graphite (EG) can increase the thermal and mechanical performance [4]. When exposed to heat, EG produces a char layer that prevents heat and oxygen transfer which is known as intumescing. Mechanical performance is dependent on amount of EG loading since the cell sizes are linearly dependent on it. Overall, the rigid foams (I-R2) proved superior. SEM Analysis: I-R2 had the most consistent spherical sizes (average cell diameter: 489 μm), which enhance the relative density the most [5]. Tensile Testing Results: I-R2 experienced the largest breaking load (103.65 lbf) and stress (289.42 psi). I-R2 also had a higher Young's Modulus compared to R1 (2.99 ksi to 2.09 ksi). Compression Testing Results: I-R2 had the highest stress at 80% deflection (360.67 psi), load (1387.48 lbf) and modulus (3.92 ksi)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Tungsten-loaded SMP foam nanocomposites with inherent radiopacity and tunable thermo-mechanical properties

Shape memory polymer (SMP) foams have been developed for use in neurovascular occlusion applications. These materials are predominantly polyurethanes that are known for their biocompatibility and tunable properties. However, these polymers inherently lack X–ray visibility, which is a significant challenge for their use as implantable materials. Herein, low density, highly porous shape memory polyurethane foams were developed with tungsten nanoparticles dispersed into the foam matrix, at increasing concentrations, to serve as a radiopaque agent. Utilizing X–ray fluoroscopy sufficient visibility of the foams at small geometries was observed. Thermal characterization of the foams indicated altered thermal response and delayed foam actuation with increasing nanoparticle loading (because of restricted network mobility). Mechanical testing indicated decreased toughness and strength for higher loading because of disruption of the SMP matrix. Altogether, filler addition imparted x–ray visibility to the SMP foams and allowed for tuned control of the transition temperature and actuation kinetics for the material.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Durability of polymeric encapsulation materials in a PMMA/glass concentrator photovoltaic system

We examined the durability of polymeric encapsulation materials using outdoor exposure at the nominal geometric concentration of 500 suns. The results for 36-month cumulative field deployment are presented for materials including: poly(ethylene-co-vinyl acetate), (EVA); polyvinyl butyral (PVB); ionomer; polyethylene/polyoctene copolymer (PO); thermoplastic polyurethane (TPU); poly(dimethylsiloxane) (PDMS); poly(diphenyl dimethyl siloxane) (PDPDMS); and poly(phenyl-methyl siloxane) (PPMS). Measurements of the field conditions including ambient temperature and ultraviolet (UV) dose were recorded at the test site during the experiment. Our measurements for the experiment included optical transmittance (with subsequent analysis of solar-weighted transmittance, UV cut-off wavelength, and yellowness index), mass, visual photography, photoelastic imaging, and fluorescence spectroscopy. While the results to date for EVA are presented and discussed, examination here focuses more on the siloxane materials. A specimen recently observed to fail by thermal decomposition is discussed in terms of the implementation of the experiment as well as its fluorescence signature, which was observed to become more pronounced with age. Modulated thermogravimetry (allowing determination of the activation energy of thermal decomposition) was performed on a subset of the siloxanes to quantify the propensity for decomposition at elevated temperatures. Supplemental, Pt-catalyst- and primer-solutions as well as peroxide-cured PDMS specimens were examined to assess the source of the luminescence. Furthermore, our results, including the change in optical transmittance, observed failure modes, and subsequent analyses of the failure modes are described in the conclusions.

14 SOLAR ENERGY↗
DOE OSTI2018

Silicone wristbands compared with traditional polycyclic aromatic hydrocarbon exposure assessment methods

Currently there is a lack of inexpensive, easy-to-use technology to evaluate human exposure to environmental chemicals, including polycyclic aromatic hydrocarbons (PAHs). This is the first study in which silicone wristbands were deployed alongside other PAH exposure assessment methodologies. Wristbands were used within an established Columbia Center for Children’s Environmental Health birth cohort and compared to two traditional personal PAH exposure assessment methods: biological sampling with urine and active air monitoring with samplers (i.e. polyurethane foam (PUF) and filter) housed in backpacks. All samplers were deployed simultaneously on 22 pregnant women for 48-hours. Each woman provided one spot urine sample at the end of the 48-hour period. Sixty-two and 20 PAHs were quantified in the wristbands and PUF/filter, respectively; and eight hydroxy-PAH (OH-PAH) metabolites were quantified in the urine. PAHs in the PUF/filter and OH-PAHs correlate significantly for two of the eight comparisons (rs=0.53 and p=0.01; rs=0.44 and p=0.04). PAHs in the wristband and OH-PAHs correlate significantly for four of the eight comparisons; 1-OH-phenanthrene and 1-OH-pyrene strongly correlate with the parent PAHs in the wristband (rs=0.76 and p=<0.0001; rs=0.66 and p=0.0009). These results suggest wristbands are more closely associated with OH-PAHs in urine than active personal air monitoring methods.

Dixon, Holly M.↗
DOE OSTI2025

Damage progression and failure of SiC/SiC composite tubes under hard-contact radial expansion

The response of silicon carbide (SiC) fiber-reinforced SiC matrix (SiC/SiC) composite cladding to mechanical interaction with fissile fuel is a knowledge gap that must be overcome to design and assess SiC-based cladding systems for advanced nuclear applications. This study developed the relevant mechanical testing capability and identified the failure behavior and the critical microstructural features and processing defects. Sections of SiC composite tube were subjected to a modified expansion-due-to-compression (EDC) test in an X-ray computed tomography microscope: a polyurethane plug pressed surrogate Al 2 O 3 into the inner walls of the SiC/SiC composite tubes to achieve hard contact. A pure EDC test with just a polyurethane plug was also performed as a reference. Through the use of displacement fields, digital volume correlation revealed inhomogeneous deformation fields in the tubes, even for pure EDC, which was related to the inherent defects in the structure. Deep learning–aided segmentation and systematic data analysis revealed that the presence of inhomogeneous deformation applied by the hard contact was exaggerated by the presence of inner surface imperfections left behind from the matrix densification process. In conclusion, the findings provide insights into the applications, highlighting the necessity for improvements in inner surface roughness and the incorporation of localized contacts in pellet–cladding mechanical interaction computational models.

Composites↗
DOE OSTI2023

Solid and gas thermal conductivity models improvement and validation in various porous insulation materials

In the past few decades, significant efforts have been made to improve the theoretical understanding of thermal transport mechanisms in thermal insulation materials and push the thermal conductivity's lower limits. However, most works focused singularly on specific types of materials, and the models used for thermal conductivity predictions are diverse - a model that fits one material might not fit others. Here, we improve and unify the gas and solid thermal conductivity models for porous materials. Through experimental characterization of several different materials as well as literature data for other materials, these models are validated. Further, we have also found that the pressure-dependent gas thermal conductivity of most materials can be well fitted by using one or two pore sizes without using a complex pore size distribution. With the refined models, we decompose the effective thermal conductivity of several thermal insulation materials into gas, solid, and radiation contributions. For cellular (polystyrene and polyurethane) foams, the relative contributions from air, solid, and radiation are 58–75%, 3–11%, 16–38%, respectively. For granular porous materials (polyurethane and silica in this work), the contributions from air, solid, and radiation are 45–66%, 34–46%, and 0–8%, respectively. This work is expected to provide guidance on the design and optimization of the next generation of thermal insulation materials, for example, through the effort of reducing gas conduction and radiation in foams and suppressing gas and solid conduction in aerogels.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Green chemistry design in polymers derived from lignin: review and perspective

The use of lignin for material and chemical applications has gained interest in recent times due to the environmental focus on using biomass for renewable materials as well as the motivation to valorize lignin as part of an integrated biorefinery. While a wealth of publications can be found for lignin-derived materials, and several reviews can be found on the topic, there are no reviews that outline and critically assess the sustainability of these protocols based on the criterion of the 12 Principles of Green Chemistry. This review assesses the literature for lignin- derived polymers over the past 20 years and highlights attempts to use biobased accompanying reagents, green solvents or solvent-less protocols, reports that replace traditionally toxic precursors (e.g. diisocyanates for polyurethanes), use mild conditions, valorize additional waste streams and prepare materials particularly biodegradable or recyclable. Here, the following work is a comprehensive and critical assessment of the green and sustainable nature of the state-of-the art of lignin-derived polymers (polyurethane, polyester, epoxy, phenolic resin, and others) utilizing actual biomass in the synthetic protocol. Each section of this review highlights and assesses published protocols that use a particularly green approach in one or more steps of the synthetic sequence. While many reports still contain traditional petroleum-derived and toxic methods along with more sustainable methods, the outline of all such green methods is able to create a landscape amidst lignin-derived polymer synthesis that points the way toward safer and more environmentally friendly materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Accumulation of microplastics in soil after long-term application of biosolids and atmospheric deposition

Land-applied biosolids can be a considerable source of microplastics in soils. Previous studies reported microplastics accumulation in soils from biosolid application, however, little is known about the contribution of atmospherically deposited microplastics to agricultural soils. In this study, we quantified and characterized microplastics in soils that have been amended with biosolids over the past 23 years. We also collected atmospheric deposition samples to determine the amount and type of plastics added to soils through atmospheric input over a period of about 2 years. Soil samples were taken from a replicated field trial where biosolids have been applied at rates of 0, 4.8, 6.9, and 9.0 t/ha every second crop. The biosolids were anaerobically digested and dewatered, and were applied by spreading onto the soil surface. Soil and atmospheric samples were extracted for microplastics by Fenton's reaction to remove organic matter followed by flotation in a zinc chloride solution to separate plastic from soil particles. Samples were analyzed for microplastics by optical microscopy and Laser Direct Infrared Imaging Analysis (LDIR). The mean number of microplastics identified from biosolids samples was 12,000 particles/kg dry biosolids. The long-term applications of biosolids to the soil led to mean plastics concentrations of 383, 500, and 361 particles/kg dry soil in the 0–10 cm depth for low, medium, and high biosolids application rates, respectively. These plastic concentrations were not significantly different from each other, but significantly higher than those found in non biosolids-amended soil (117 particles/kg dry soil). The dominant plastic types by number found in biosolids were polyurethane, followed by polyethylene, and polyamide. The most abundant plastics in soil samples were polyurethane, polyethylene terephthalate, polyamide, and polyethylene. Atmospheric deposition contributed to 15 particles/kg dry soil per year and was mainly composed of polyamide fibers. In conclusion, this study shows that long-term application of biosolids led to an accumulation of microplastics in soil, but that atmospheric deposition also contributes a considerable input of microplastics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Variation of Aliphatic Diisocyanates in Bio-Based TPUs

The utilization of bio-based materials for polymer production poses a challenge to both the industrial and academic sectors due to the availability and production costs of the necessary raw materials. Diisocyanates necessary for polyurethane synthesis have posed a particular challenge, given the paucity of natural diamine precursors for traditional phosgenation. We recently developed a phosgene-free flow chemistry methodology that allows for the safe, efficient, and scalable preparation of diisocyanates from naturally produced diacids. This chemistry broadens the potential for the development of renewable diisocyanates for a broad variety of applications. Here, we expand upon this work by demonstrating the scaled production of a panel of bio-based linear, aliphatic diisocyanates, with chain lengths ranging from four to eight carbons in good yields of 57–81% and high purity (~97%). Furthermore, these are applied to the synthesis of thermoplastic polyurethanes (TPUs) containing up to a 100% renewable carbon content. TPUs formulated using shorter carbon-chained diisocyanates displayed a higher tensile strength compared to those formulated using longer chains. Ready access to diisocyanates of varying chain length affords the ability to tailor TPU properties through careful selection of the diisocyanate, polyol, and chain extender, offering hard and soft TPUs for multiple end-use applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Chemically Active, Porous 3D-Printed Thermoplastic Composites

Metal-organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms. To address this, we report the production of MOF-thermoplastic polymer composites accessed via a standard 3D printer. MOFs (Zeolitic imidazolate framework; ZIF-8) were successfully incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices, extruded into filaments, and utilized for on-demand access to 3D structures by fused-deposition modeling. Printed rigid PLA-MOF composites displayed good structural integrity, high surface area ((SA)avg = 531 m2 g-1) and hierarchical pore features. Flexible TPU-MOF composites (SAavg = 706 m2 g-1) were achieved by employing a sacrificial fluoropolymer readily removed post-printing. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent MOF. The fabrication strategies can be extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically-active structures.

Additive Manufacturing, Metal-Organic Framework, 3↗
DOE OSTI2024

Engineering the Novel Extremophile Alga Chlamydomonas pacifica for High Lipid and High Starch Production as a Path to Developing Commercially Relevant Strains

Microalgae offer a compelling platform for the production of commodity products, due to their superior photosynthetic efficiency, adaptability to nonarable lands and nonpotable water, and their capacity to produce a versatile array of bioproducts, including biofuels and biomaterials. However, the scalability of microalgae as a bioresource has been hindered by challenges such as costly biomass production related to vulnerability to pond crashes during large-scale cultivation. This study presents a pipeline for the genetic engineering and pilot-scale production of biodiesel and thermoplastic polyurethane precursors in the extremophile species Chlamydomonas pacifica. This extremophile microalga exhibits exceptional resilience to high pH (>11.5), high salinity (up to 2% NaCl), and elevated temperatures (up to 42 °C). Initially, we evolved this strain to also have a high tolerance to high light intensity (>2000 μE/m 2 /s) through mutagenesis, breeding, and selection. We subsequently genetically engineered C. pacifica to significantly enhance lipid production by 28% and starch accumulation by 27%, all without affecting its growth rate. We demonstrated the scalability of these engineered strains by cultivating them in pilot-scale raceway ponds and converting the resulting biomass into biodiesel and thermoplastic polyurethanes. This study showcases the complete cycle of transforming a newly discovered species into a commercially relevant commodity production strain. This research underscores the potential of extremophile algae, including C. pacifica, as a key species for the burgeoning sustainable bioeconomy, offering a viable path forward in mitigating environmental challenges and supporting global bioproduct demands.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Efficient secretion of a plastic degrading enzyme from the green algae Chlamydomonas reinhardtii

Abstract Plastic pollution has become a global crisis, with microplastics contaminating every environment on the planet, including our food, water, and even our bodies. In response, there is a growing interest in developing plastics that biodegrade naturally, thus avoiding the creation of persistent microplastics. As a mechanism to increase the rate of polyester plastic degradation, we examined the potential of using the green microalgaChlamydomonas reinhardtiifor the expression and secretion of PHL7, an enzyme that breaks down post-consumer polyethylene terephthalate (PET) plastics. We engineeredC. reinhardtiito secrete active PHL7 enzyme and selected strains showing robust expression, by using agar plates containing a polyester polyurethane (PU) dispersion as an efficient screening tool. This method demonstrated the enzyme’s efficacy in degrading ester bond-containing plastics, such as PET and bio-based polyurethanes, and highlights the potential for microalgae to be implemented in environmental biotechnology. The effectiveness of algal-expressed PHL7 in degrading plastics was shown by incubating PET with the supernatant from engineered strains, resulting in substantial plastic degradation, confirmed by mass spectrometry analysis of terephthalic acid formation from PET. Our findings demonstrate the feasibility of polyester plastic recycling using microalgae to produce plastic-degrading enzymes. This eco-friendly approach can support global efforts toward eliminating plastic in our environment, and aligns with the pursuit of low-carbon materials, as these engineered algae can also produce plastic monomer precursors. Finally, this data demonstratesC. reinhardtiicapabilities for recombinant enzyme production and secretion, offering a “green” alternative to traditional industrial enzyme production methods.

Science & Technology - Other Topics↗
DOE OSTI2024

Efficient secretion of a plastic degrading enzyme from the green algae Chlamydomonas reinhardtii

AbstractPlastic pollution has become a global crisis, with microplastics contaminating every environment on the planet, including our food, water, and even our bodies. In response, there is a growing interest in developing plastics that biodegrade naturally, thus avoiding the creation of persistent microplastics. As a mechanism to increase the rate of polyester plastic degradation, we examined the potential of using the green microalgaChlamydomonas reinhardtiifor the expression and secretion of PHL7, an enzyme that breaks down post-consumer polyethylene terephthalate (PET) plastics. We engineeredC. reinhardtiito secrete active PHL7 enzyme and selected strains showing robust expression, by using agar plates containing a polyester polyurethane (PU) dispersion as an efficient screening tool. This method demonstrated the enzyme’s efficacy in degrading ester bond-containing plastics, such as PET and bio-based polyurethanes, and highlights the potential for microalgae to be implemented in environmental biotechnology. The effectiveness of algal-expressed PHL7 in degrading plastics was shown by incubating PET with the supernatant from engineered strains, resulting in substantial plastic degradation, confirmed by mass spectrometry analysis of terephthalic acid (TPA) formation from PET. Our findings demonstrate the feasibility of polyester plastic recycling using microalgae to produce plastic-degrading enzymes. This eco-friendly approach can support global efforts toward eliminating plastic in our environment, and aligns with the pursuit of low-carbon materials, as these engineered algae can also produce plastic monomer precursors. Finally, this data demonstratesC. reinhardtiicapabilities for recombinant enzyme production and secretion, offering a “green” alternative to traditional industrial enzyme production methods.Graphical Abstract

Molino, João Vitor Dutra (ORCID:0000000324759807)↗
DOE OSTI2021

Experimental Investigation on the Performance Loss of Cross-Linked Polymers During Photo-Oxidative Aging

Abstract Polymeric substances have seen an unprecedented integration in countless applications and fields of life, subjecting them to a broad range of environmental conditions, which can cause a form of damage to the structural and mechanical properties of these components known as aging. In this study we investigate the effects of the degradation of polymeric materials due to the extended exposure to sunlight, which can be simulated through controlled photo-oxidative aging using ultraviolet (UV) radiation as the main catalyst of this phenomenon. The effects on mechanical behavior and chemical properties of four polymeric materials with different mechanical characteristics was accordingly monitored throughout the study. The materials range in hardness with the polyurethane adhesive being the hardest and acting plastically, followed by an acrylic which exhibits greater hardening with time, a polyurethane sealant, which behaves in an elastomeric manner, and a silicon sealant, which is the softest of the set. Samples were prepared and subjected to UV radiation at three different temperatures namely 45, 60 and 80°C, for different aging periods ranging from 1 day for higher temperatures to 150 days for lower ones. The samples were then subjected to the Fourier transform Infrared spectroscopy (FTIR) test to monitor the change in the chemical composition of the materials along the aging durations and conditions. The materials were then subjected to mechanical testing along two modes of mechanical loading, which are a simple tension until failure and a double-cyclic test with progressively increasing strain limits after every two successful cycles until the sample reaches failure. The samples are loaded at constant strain rates throughout both tests. These tests revealed the change of behavior of our materials along the aging periods and conditions. The changes in mechanical behavior vary across each individual material depending on the aging temperature and period, with the changes ranging from hardening to softening, embrittlement or an increase in the maximum strain the material can endure before failure. A general trend would be that most materials become harder after photo-oxidation, however due to the range of temperatures in the aging conditions, thermo-oxidation, which causes softening in some of the polymers, has an increasingly notable effect at higher temperatures. A visible correlation can be noted between the change in mechanical behavior and a change in absorbance of Infrared Radiation (IR) in the FTIR spectrum, as the greater the crosslinking throughout the polymer matrix, the lower the absorbance of IR radiation due to the increased stiffness of the overall macro-molecular structure.

Korayem, Abd-Elrahman↗
DOE OSTI2016

TH-CD-207B-10: Effect of CT Reconstruction Filter On Measured Hounsfield Values in Lung Nodules

Purpose: Measured Hounsfield numbers in CT are used by radiologists to determine the presence of calcium or fat in lung nodules, either of which suggests a benign diagnosis. However, substantial variations in Hounsfield number may arise due to the use of different reconstruction parameters such as the filter/kernel, leading to measurement inaccuracies. This quality improvement project was developed to demonstrate measurement pitfalls and to identify acceptable conditions for incorporating Hounsfield values as a factor in lung nodule diagnosis. Methods: 12 mm-diameter spheres of polyurethane and urethane foam were placed into an anthropomorphic chest phantom, and 10 mm-diameter tubes with varying iodine concentrations were placed into a 16 cm PMMA cylindrical phantom. Additionally, 11 mm-diameter PMMA and HDPE spheres were placed in a 10 cm PMMA cylindrical phantom. Phantoms were scanned at 120 kVp using a Siemens Biograph mCT and on a Philips iCT and reconstructed using various reconstruction filters. Results: For the Siemens system, both sharp kernels and smooth kernels altered the Hounsfield numbers. Hounsfield numbers varied within a range of 8.9 HU for urethane foam and varied within 58.7 HU for polyurethane. The iodine measurements varied up to 37.9 HU for the lowest concentration. For the Philips system, Hounsfield numbers were relatively consistent but were higher for the “Detail” and “Lung Enhanced” filters, varying by 36.9 HU for PMMA and 15.9 HU for HDPE. Conclusion: Reconstruction filters can change the measured Hounsfield numbers of nodular objects, especially with detail-enhancing (sharpening) filters commonly used in lung imaging. Measured values should only be used for diagnostic decision support with filters that have demonstrated accuracy and consistency. While filter accuracy statements are available from manufacturers, radiologists are likely not aware of the extent of potential variations that can occur in a clinical setting.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

The Addition of Graphene to Polymer Coatings for Improved Weathering

Graphene nanoflakes in different weight percentages were added to polyurethane top coatings, and the coatings were evaluated relative to exposure to two different experimental conditions: one a QUV accelerated weathering cabinet, while the other a corrosion test carried out in a salt spray chamber. After the exposure tests, the surface morphology and chemical structure of the coatings were investigated via atomic force microscopy (AFM) and Fourier transform infrared (FTIR) imaging. Our results show that the addition of graphene does in fact improve the resistance of the coatings against ultraviolet (UV) degradation and corrosion. It is believed that this process will improve the properties of the polyurethane top coating used in many industries against environmental factors.

Nuraje, Nurxat↗
DOE OSTI2019

Solubility and volume swell of fuel system elastomers with ketone blends of E10 gasoline and blendstock for oxygenate blending (BOB)

The compatibility of key infrastructure elastomers with five ketone molecules was assessed via solubility studies and volume swell measurements. The elastomer materials included two fluorocarbons, six acrylonitrile butadiene rubbers (NBRs), and one each of fluorosilicone, neoprene, polyurethane, styrene butadiene rubber (SBR), and silicone. The ketone molecules included acetone, 2-butanone, 2-pentanone, 2-nonanone, and cyclopentanone. The ketones were added to gasoline containing 10% ethanol (E10) and a blendstock for oxygenate blending (BOB) in levels ranging from 0% to 30% by volume. The elastomers were exposed for 4 weeks in each test fluid. The solubility was modeled using Hansen solubility parameters and the volume change was determined for each material and test fuel. In general, the volume swell increased with ketone content and corresponded well to the predicted solubilities. In most cases, the highest level of swelling occurred with added cyclopentanone and acetone, while 2-nonanone produced the lowest levels of volume expansion. The chain length of the straight ketones was found to affect the volume swell behavior as volume expansion decreased with increasing chain length. This behavior is attributed to the reduction in polarity and hydrogen bonding with chain length. Neoprene, SBR, and silicone exhibited poor compatibility with the ketone molecules at all blend levels. Fluorocarbon and fluorosilicone also showed poor compatibility but may be suitable for use as static seals in very low blend levels with 2-nonanone. The results were more mixed for polyurethane and the NBRs. In general, better compatibility (low volume swell) was observed for mixtures containing BOB than for E10. This is due to the lower polarity and hydrogen bonding of the BOB.

10 SYNTHETIC FUELS↗
DOE OSTI2017

Modeling cookoff of HMX based PBX explosives

We have previously developed a PBX 9501 cookoff model for the plastic bonded explosive PBX 9501 consisting of 95 wt% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine (HMX), 2.5 wt% Estane® 5703 (a polyurethane thermoplastic), and 2.5 wt% of a nitroplasticizer (NP): BDNPA/F, a 50/50 wt% eutectic mixture bis(2,2-dinitropropyl)-acetal (BDNPA) and bis(2,2-dinitropropyl)-formal (BDNPF). This fivestep model includes desorption of water, decomposition of the NP to form NO 2 , reaction of the NO 2 with Estane and HMX, and decomposition of HMX [1]. This model has been successfully validated with data from six laboratories with scales ranging from 2 g to more than 2.5 kg of explosive. We have determined, that the PBX 9501 model can be used to predict cookoff of other plastic bonded explosives containing HMX and an inert binder, such as LX-04 consisting of 85 wt% HMX and 15 wt% Viton A (vinylidine fluoride/hexafluoropropylene copolymer), LX-07 (90 wt% HMX and 10 wt% Viton A), LX- 10-0 (95 wt% HMX and 5 wt% Viton A), and LX-14 consisting of 95.5 wt % HMX and 4.5 wt% Estane® 5702-F1 (a polyurethane thermoplastic). Normally our cookoff models are verified using Sandia’s Instrumented Thermal Initiation (SITI) experiment. However, SITI data for LX-04, LX-07, LX-10-0, and LX-14 are not available at pressed density; although, some molding powder SITI data on LX-10-0 and LX-14 exists. Tarver and Tran [2] provide some one-dimensional time-to-explosion (ODTX) data for these explosives. The applicability of the PBX 9501 model to LX-04, LX-07, LX-10-0, AND LX-14 was made using this ODTX data [2]. The PBX 9501 model is applied to these other explosives by accounting for the correct amount of HMX in the explosive and limiting the NP reaction. We have found the PBX 9501 model to be useful for predicting the response of these PBXs to abnormal thermal environments such as fire.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗