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Elastomers having molecular weights above 1 million made by twostage polymerization. Two-stage process proves far more successful than synthesis from reactive monomers. Process involves synthesis of silanolterminated prepolymer and subsequent extension of prepolymer chain with additional aminosilane monomer. Multistage method allows chain-extending monomer added in precise amounts between stages.
Elastomers enhance thermal and mechancial properties. Capable of performing in extreme thermal/oxidative environments and having molecular weights above 10 to the sixth power prepared and analyzed in laboratory experiments. Made of methylvinylsilphenylene-siloxane terpolymers, new materials amenable to conventional silicone-processing technology. Similarly formulated commercial methyl-vinyl silicones, vulcanized elastomers exhibit enhance thermal/oxidative stability and equivalent or superior mechanical properties.
This report documents the Interim Measure (IM) completed at Un-Numbered Operational Areas (UNOA) potential release location (PRL) 229, at Kennedy Space Center (KSC), Florida. This document has been prepared for the National Aeronautics and Space Administration (NASA), in accordance with HydroGeoLogic, Inc.’s (HGL) Contract 80KSC019D0012, Task Order 80KSC019F0224. The purpose of this IM report is to document the field results of the 2022 IM conducted between December 13, 2021, and February 11, 2022, and to present the recommendations based on the IM findings. IM activities were completed at the UNOA PRL 229 to remove railroad ties and benzo(a)pyrene equivalent (BAPE)/total recoverable petroleum hydrocarbons (TRPH)-affected soil in accordance with the IM Work Plan (IMWP) (Jacobs/CORE, 2019a). The objectives of the IM were to mitigate human health risks by reducing site contaminants to the residential soil cleanup target level (SCTL) based on the 95 percent upper confidence limit on the mean. A second objective was to reduce low molecular weight and high molecular weight polynuclear aromatic hydrocarbon (PAH) concentrations below ecological screening values for terrestrial receptors. Prior to excavation operations, railroad ties from all areas were consolidated. In total, 50.67 tons of railroad ties were transported from the site to JED Landfill in St. Cloud, Florida. The cumulative excavation footprint spanned an area of 9,710 square ft. In total, 908.54 tons of soil was transported from the site to JED Landfill. To backfill the excavation area, 880 cubic yards of clean fill was trucked to the site from S&LMaterials, Inc. borrow pit in Christmas, Florida. Following completion of backfill, the site restoration activities included grading the disturbed areas to match the existing elevations and vegetation planting by the site restoration subcontractor. The IM implementation activities were presented to the KSC Remediation Team during its meeting on May 3, 2022. The Remediation Team reached consensus on the completion of the IM reducing the area affected by BAPE/TRPH above the State of Florida residential soil cleanup target levels.
Non-brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants.
Non brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants.
An axenic culture of Skeletonema costatum was grown to late-log phase to examine the molecular weight distribution and the biochemical composition of high molecular weight dissolved organic matter released in the absence of actively growing bacteria. A second culture was grown in a 5 m(exp 3) mesocosm and placed in darkness for a period of 51 days to examine the impact of phytoplankton bloom dynamics and microbial decomposition on dissolved (DOM) and particulate organic matter (POM) composition. DOM was separated using tangential-flow ultrafiltration into three nominal size fractions: LDOM (less than 1 kDa DOM), HDOM (1-30 kDa) and VHDOM (30 kDa-0.2 micron) and characterized. Both axenic and mesocosm diatom blooms released 28-33% of net primary production as dissolved organic carbon (DOC). In the axenic culture, HDOM and LDOM each comprised about half of the diatom-released DOC with less than l% as VHDOM. Diatoms from both experiments released carbohydrate-rich high molecular weight DOM. Much of the axenic diatom-released high molecular weight DOC could be chemically characterized (61% of HDOM and 78% of VHDOM) with carbohydrates as the primary component (45% of HDOM and 55% of VHDOM). Substantial amounts of hydrolyzable amino acids (16% of HDOM and 22% of VHDOM) and small amounts of lipids (less than 1%) were also released. Proportions of recognizable biochemical components in DOM produced in the mesocosm bloom were lower compared to the axenic culture. The presence of bacterial fatty acids and peptidoglycan-derived D-amino acids within high molecular weight fractions from the mesocosm bloom revealed that bacteria contributed a variety of macromolecules to DOM during the growth and decay of the diatom bloom. Release of significant amounts of DOC by diatoms demonstrates that DOM excretion is an important component of phytoplankton primary production. Similarities in high molecular weight DOM composition in marine waters and diatom cultures highlight the importance of phytoplankton to DOM composition in the ocean.
The present invention blocks and/or attenuates the upstream travel of acoustic disturbances or sound waves from a flight vehicle or components of a flight vehicle traveling at subsonic speed using a local injection of a high molecular weight gas. Additional benefit may also be obtained by lowering the temperature of the gas. Preferably, the invention has a means of distributing the high molecular weight gas from the nose, wing, component, or other structure of the flight vehicle into the upstream or surrounding air flow. Two techniques for distribution are direct gas injection and sublimation of the high molecular weight solid material from the vehicle surface. The high molecular weight and low temperature of the gas significantly decreases the local speed of sound such that a localized region of supersonic flow and possibly shock waves are formed, preventing the upstream travel of sound waves from the flight vehicle.
Two new polyethers, poly /hexafluoropentamethylene tetrafluoro-p-phenylene ether/ and a completely hydroxyl-terminated polyether, is prepared by reactions of hexafluorobenzene with hexafluoropentanediol. The polyethers can be prepared as low molecular weight oils, as intermediate molecular weight waxes, or as high molecular weight elastomers.
High-molecular weight, high-temperature, highly optically transparent films suitable for electronic and aerospace applications were prepared based on a novel methylene-bridged dianhydride 3,3-prime bis(3,4-dicarboxyphenoxy) diphenylmethane dianhydride (PDMDA). All films had lower dielectric constants and significantly higher optical transparency than the commercial Kapton H film, with air-cured films having slightly higher dielectric constants and lower optical transparency than vacuum films, due to oxidative cross-linking.
Mechanical testing of the elastic and viscoelastic response of an advanced thermoplastic polyimide (LaRC-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The notched tensile strength was shown to be a strong function of both molecular weight and temperature, whereas stiffness was only a strong function of temperature. A critical molecular weight was observed to occur at a weight average molecular weight of M, approx. 22,000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Low, molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. Furthermore, low molecular weight materials have increased creep compliance and creep compliance rate, and are more sensitive to temperature than the high molecular weight materials. At long timescales (less than 1100 hours) physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested. Low molecular weight materials are less influenced by the effects of physical aging.
Synthesis via aromatic nucleophilic displacement yields new high-molecular-weight polymers. Polymers exhibited good mechanical and thermal properties. Synthetic route provided high-molecular-weight POX of new chemical structure, potentially more economical. Availability of large variety of activated aromatic dihalides, facilitates variation of chemical structures. Exhibit properties making them useful as films. Also useful in coatings, adhesives, moldings, and composites.
Size exclusion chromatography was used to determine the chemical degradation of MIL-L-27502 oil samples from a gas turbine engine test run at a bulk oil temperature of 216 C. Results revealed a progressive loss of primary ester and additive depletion and the formation of higher molecular weight products with time. The high molecular weight products absorbed strongly in the ultraviolet indicating the presence of chromophoric groups.
Spacecraft environmental control and life support systems (ECLSS) include a number of air revitalization (AR) technologies to provide breathable air and a comfortable living environment to the crew. Crew health and comfort is ensured by controlling human produced CO2 (1 kg person-1 day-1) and water vapor (~2 kg person-1 day-1), and by removing trace contaminants (TCs) from cabin air. These life support functions on-board the International Space Station (ISS) are carried out by the Carbon Dioxide Removal Assembly (CDRA), the Water Processor Assembly (WPA), and the trace contaminant control system (TCCS). During the development of the TCCS, new analytical and theoretical methods were developed in the 1970s for characterizing adsorption and desorption characteristics of activated carbons for the purpose of designing suitable AR technologies required for controlling airborne trace contaminants within spacecraft cabins during long exploration missions. The TCCS removes harmful volatile organic compounds and other trace contaminants from the circulating air. It consists of a granular activated carbon (GAC) bed for the removal of high molecular weight contaminants and ammonia followed by a heated catalytic bed for low molecular weight hydrocarbons. The high temperature catalytic oxidizer (HTCO) of the TCCS, which operates at 400°C and requires 120W average power, removes low molecular weight compounds such as carbon monoxide (CO), formaldehyde (CH2O), and methane (CH4), that pass through the GAC bed. The Air Revitalization Laboratory at the Kennedy Space Center (KSC) was established to develop new analytical methods for evaluating emerging ECLSS technologies for use in future AR architectures. General properties of adsorbents and catalysts are required for trace contaminant control system design calculations and vendor-supplied data are seldom available at relevant process conditions of interest to spacecraft cabin applications. To address this shortcoming, appropriate testbeds were developed to measure the desired properties of AR technologies being considered for use in ECLS architectures. Generally, the testbeds developed at KSC challenge the test media (activated carbon, impregnated activated carbon, catalysts, zeolites, solid amines, or pleated filters) with simulated spacecraft gas streams containing representative mixtures of trace contaminants (volatile organic compounds, ammonia, CO, CO2, or siloxanes) at the flow rates, temperatures, and relative humidity that will be encountered within manned spacecraft. Work performed at KSC funded by NASA’s Advanced Exploration (AES) Program has included: Identifying candidate sorbents to replace commercially obsolete impregnated carbons for NH3 control within the TCCS, characterizing their adsorptive capacities using simulated spacecraft gas streams, and ranking their appropriateness in various AR applications; evaluating novel low temperature catalysts for controlling CO and formaldehyde by traditional and photocatalytic methods for trace contaminant control; development of analytical methods to assess regenerable solid amine performance for CO2 control via pressure swing adsorption. The Air Revitalization lab was also funded to study trace contaminant control by other NASA programs. These include: screening of candidate sorbents for the design of new Charcoal HEPA Integrated Particle Scrubber (CHIPS) filters for removing siloxanes from cabin air; characterizing the performance of an impregnated activated carbon at low humidity for use in ORION ECLS; screening of sorbents for protecting the Sabatier 2.0 catalyst from DMSO2, siloxanes, NH3, and solid amine byproducts.
Gel Permeation Chromatography (GPC) was used to analyze poly(arylene ether phosphine oxide)s whose backbones were identical except for the ketone content and placement. These samples were exposed to low Earth orbit environment (predominantly atomic oxygen) on space shuttle flights. The materials and their unexposed controls were then characterized by GPC to investigate the effect of atomic oxygen on the molecular weight distributions. Analysis of the soluble portion of the samples revealed that there was significant loss of high molecular weight species. The presence of insoluble material also suggested that crosslinking was induced by the atomic oxygen exposure and that this very likely occurred at the high molecular weight portion of the molecular weight distribution.
As part of a continuing effort to prepare novel thermally stable high-performance polymers, poly(arylene ether isoxazole)s have been prepared by fluoride ion-catalyzed aromatic nucleophilic substitution reactions with bis(trimethylsiloxyphenyl) isoxazoles and activated bisarylhalides in diphenyl sulfone. Initial investigation involving the preparation of these materials with isoxazole bisphenols and activated bisarylhalides in the presence of potassium carbonate indicated that, under reaction conditions necessary to prepare high-molecular-weight materials, the isoxazole monomer was converted to an enamino ketone. This side reaction was avoided by using fluoride as a base. However, trimethylsilyl ether derivatives of the isoxazole bisphenols were required in these polymerizations for the preparation of high-molecular-weight materials. Moderate to high inherent viscosity eta(sub inh): 0.43-0.87 dl/g) materials with good thermal stability (air: 409-477 C, helium: 435-512 C) can be prepared by the silyl ether method. Glass transition temperatures ranged from 182 to 225 C for polymers with phenyl pendants and from 170 to 214 C for those without. Molecular weight control by 2% endcapping and the incorporation of a phenyl pendant at the 4 position of the isoxazole is necessary to yield polymers soluble in polar aprotic solvents at room temperature. There is evidence, however, indicating the existence of crosslinks between the polymer chains when the silyl ether approach is utilized.
The otoconial matrix (OM) of chicks (Gallus domesticus) inner ear was analyzed. Histochemically the OM was reacted with phosphotungstic acid (PTA) and immunohistochemically with the monoclonal antibody antikeratan sulfate (antiKS). The OM was digested with the enzyme endo-beta-galactosidase (E beta Galase) or separated by 1D and 2D gel electrophoresis. PTA which reacts with glycoproteins precipitated the OM, suggesting that the OM contains glycoproteins. A central core in each crystal had no PTA staining, suggesting that the core lacked glycoproteins. Anti KS antibody stained the OM with increased density in older embryos as determined by color thresholding. E beta Galase, which cleaves the lactosamine repeating units in KS, decreased the immunostain by 30% in the OM and by 20% in the cartilage. The OM from the utricle, saccule and macula lagena contained similar molecular weight bands. Five dense bands in the OM were less dense in tissue and blood controls, suggesting that such bands are enriched in the OM. Isoelectric focusing of the OM showed a negatively charged high molecular weight smear not present in blood and faint in tissue controls. The high affinity of the OM for the cationic PTA stain, the strong immunohistochemical reaction of the OM with anti KS antibody and high molecular weight negative smear in 2D gels taken together suggest that: a) the OM contains large amounts of glycoproteins and glycans, one of which is keratan sulfate, because its immuno stain with antiKS antibody was decreased by the enzyme E beta Galase, b) the utricle, saccule and macula lagena may have similar composition, and c) the concentration of KS may increase gradually until complete mineralization of the OM is reached.
Candidate polyphosphazene polymers were investigated to develop a fire-resistant, thermally stable and flexible open cell foam. The copolymers were prepared in several mole ratios of the substituent side chains and a (nominal) 40:60 derivative was selected for formulation studies. Synthesis of the polymers involved solution by polymerization of hexachlorophosphazene to soluble high molecular weight poly(dichlorophosphazene), followed by derivatization of the resultant polymer in a normal fashion to give polymers in high yield and high molecular weight. Small amounts of a cure site were incorporated into the polymer for vulcanization purposes. The poly(aryloxyphosphazenes) exhibited good thermal stability and the first polymer mentioned above exhibited the best thermal behavior of all the candidate polymers studied.
Several aspects of research on thermoplastics as toughness modifiers are discussed, including the contribution of the backbone chemistry and the concentration of the poly(arylene ether) thermoplastic to fracture toughness, influence of the molecular weight of the poly(arylene ether) thermoplastic on neat resin fracture toughness, and the morphology of the thermoplastic modified networks. The results show that fracture toughness of brittle bismaleimide resins can be improved significantly with poly(arylene ether) thermoplastic levels of 20 percent by weight, and that high molecular weight poly(arylene ether) based on bisphenol A provides the highest degree of toughening. Preliminary composite evaluation shows that improvements in neat resin toughness translate into carbon fabric composite.