Carbon composite bipolar plate for high-temperature proton exchange membrane fuel cells (HT-PEMFCs)

NASA Astrophysics Data System (ADS)

Lee, Dongyoung; Lee, Dai Gil

2016-09-01

A carbon/epoxy composite bipolar plate is an ideal substitute for the brittle graphite bipolar plate for lightweight proton exchange membrane fuel cells (PEMFCs) because of its high specific strength and stiffness. However, conventional carbon/epoxy composite bipolar plates are not applicable for high-temperature PEMFCs (HT-PEMFCs) because these systems are operated at higher temperatures than the glass transition temperatures of conventional epoxies. Therefore, in this study, a cyanate ester-modified epoxy is adopted for the development of a carbon composite bipolar plate for HT-PEMFCs. The composite bipolar plate with exposed surface carbon fibers is produced without any surface treatments or coatings to increase the productivity and is integrated with a silicone gasket to reduce the assembly cost. The developed carbon composite bipolar plate exhibits not only superior electrical properties but also high thermo-mechanical properties. In addition, a unit cell test is performed, and the results are compared with those of the conventional graphite bipolar plate.

Structure/Property Relationships of Cyanate Ester Resins from Renewable Sources

DTIC Science & Technology

2013-04-11

derived from lignin . These materials possess favorable thermal and water uptake properties with dry glass transition temperatures above 200°C and wet...distribution is unlimited. Creosol as a Monomer Source 7 • Input material cost is an important consideration for cyanate ester resins • Lignin is...from lignin • Oxidative and reductive coupling reactions lead to precursor phenols, which are then treated with cyanogen bromide to generate cyanate

Building ultramicropores within organic polymers based on a thermosetting cyanate ester resin.

PubMed

Zhang, Bufeng; Wang, Zhonggang

2009-09-07

Ultramicropores with high surface areas (>530 m(2) g(-1)) and narrow micropore size distribution (4-6 A) were engineered within a new cyanate ester resin, extending the microporous concept (<20 A) to general thermosetting resins in the area of polymer chemistry.

Recent progress and tests of radiation resistant impregnation materials for Nb3Sn coils

NASA Astrophysics Data System (ADS)

Bossert, R.; Krave, S.; Ambrosio, G.; Andreev, N.; Chlachidze, G.; Nobrega, A.; Novitski, I.; Yu, M.; Zlobin, A. V.

2014-01-01

Fermilab is collaborating with Lawrence Berkeley National Laboratory (LBNL) and Brookhaven National Laboratory (BNL) (US-LARP collaboration) to develop a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade. An important component of this work is the development of materials that are sufficiently radiation resistant for use in critical areas of the upgrade. This paper describes recent progress in characterization of materials, including the baseline CTD101K epoxy, cyanate ester blends, and Matrimid 5292, a bismaleimide-based system. Structural properties of "ten stacks" of cable impregnated with these materials are tested at room and cryogenic temperatures and compared to the baseline CT-101K. Experience with potting 1 and 2 meter long coils with Matrimid 5292 are described. Test results of a single 1-m coil impregnated with Matrimid 5292 are reported and compared to similar coils impregnated with the traditional epoxy.

Cyanate Ester and Phthalonitrile Impregnated Carbon Ablative TPS

NASA Technical Reports Server (NTRS)

Boghozian, Tane; Stackpoole, Margaret M.; Gasch, Matt

2016-01-01

Phenolic resin has extensive heritage as a TPS (Thermal Protection Systems) material, however, alternative resin systems such as Cyanate Ester and Phthalonitrile may offer improved performance compared to state-of-the-art phenolic resin. These alternative resin systems may have higher char yield, higher char strength, lower thermal conductivity and improved mechanical properties. In current work at NASA Ames alternative resin systems were uniformly infused into fibrous substrates and preliminary properties characterized. The density of the cyanate ester infused in fibrous substrate ranged from 0.25-0.3 grams per cubic centimeter compared to PICA (Phenolic resin impregnated carbon ablative) having a density of approximately 0.25 grams per cubic centimeter. The density of Phthalonitrile varies from 0.22-0.25 grams per cubic centimeter. Initial formulations of these new resin systems were recently tested at the LARC HyMETs (Hypersonic Materials Environmental Test System) facility to evaluate their performance and data such as back face temperature, char yield, and recession are compared to PICA. Cyanate Ester and Phthalonitrile impregnated carbon ablative samples showed comparable performance to phenolic resin impregnated carbon ablative samples.

Graphite/Cyanate Ester Face Sheets for Adaptive Optics

NASA Technical Reports Server (NTRS)

Bennett, Harold; Shaffer, Joseph; Romeo, Robert

2008-01-01

It has been proposed that thin face sheets of wide-aperture deformable mirrors in adaptive-optics systems be made from a composite material consisting of cyanate ester filled with graphite. This composite material appears to offer an attractive alternative to low-thermal-expansion glasses that are used in some conventional optics and have been considered for adaptive-optics face sheets. Adaptive-optics face sheets are required to have maximum linear dimensions of the order of meters or even tens of meters for some astronomical applications. If the face sheets were to be made from low-thermal-expansion glasses, then they would also be required to have thicknesses of the order of a millimeter so as to obtain the optimum compromise between the stiffness needed for support and the flexibility needed to enable deformation to controlled shapes by use of actuators. It is difficult to make large glass sheets having thicknesses less than 3 mm, and 3-mm-thick glass sheets are too stiff to be deformable to the shapes typically required for correction of wavefronts of light that has traversed the terrestrial atmosphere. Moreover, the primary commercially produced candidate low-thermal-expansion glass is easily fractured when in the form of thin face sheets. Graphite-filled cyanate ester has relevant properties similar to those of the low-expansion glasses. These properties include a coefficient of thermal expansion (CTE) of the order of a hundredth of the CTEs of other typical mirror materials. The Young s modulus (which quantifies stiffness in tension and compression) of graphite-filled cyanate ester is also similar to the Young's moduli of low-thermal-expansion glasses. However, the fracture toughness of graphite-filled cyanate ester is much greater than that of the primary candidate low-thermal-expansion glass. Therefore, graphite-filled cyanate ester could be made into nearly unbreakable face sheets, having maximum linear dimensions greater than a meter and thicknesses of the order of a millimeter, that would satisfy the requirements for use in adaptive optics.

Gas Evolution from Insulating Materials for Superconducting Coil of Iter by Gamma Ray Irradiation at Liquid Nitrogen Temperature

NASA Astrophysics Data System (ADS)

Idesaki, A.; Koizumi, N.; Sugimoto, M.; Morishita, N.; Ohshima, T.; Okuno, K.

2008-03-01

A laminated material composed of glass cloth/polyimide film/epoxy resin will be used as an insulating material for superconducting coil of International Thermonuclear Experimental Reactor (ITER). In order to keep safe and stable operation of the superconducting coil system, it is indispensable to evaluate radiation resistance of the material, because the material is exposed to severe environments such as high radiation field and low temperature of 4 K. Especially, it is important to estimate the amount of gases evolved from the insulating material by irradiation, because the gases affect on the purifying system of liquid helium in the superconducting coil system. In this work, the gas evolution from the laminated material by gamma ray irradiation at liquid nitrogen temperature (77 K) was investigated, and the difference of gas evolution behavior due to difference of composition in the epoxy resin was discussed. It was found that the main gases evolved from the laminated material by the irradiation were hydrogen, carbon monoxide and carbon dioxide, and that the amount of gases evolved from the epoxy resin containing cyanate ester was about 60% less than that from the epoxy resin containing tetraglycidyl-diaminophenylmethane (TGDDM).

Evaluation of bisphenol E cyanate ester for the resin-injection repair of advanced composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lio, Wilber Yaote

2009-12-01

This thesis is a compilation of a general introduction and literature review that ties together the subsequent chapters which consist of two journal articles that have yet to be submitted for publication. The overall topic relates to the evaluation and application of a new class of cyanate ester resin with unique properties that lend it applicable to use as a resin for injection repair of high glass transition temperature polymer matrix composites. The first article (Chapter 2) details the evaluation and optimization of adhesive properties of this cyanate ester and alumina nanocomposites under different conditions. The second article (Chapter 3)more » describes the development and evaluation of an injection repair system for repairing delaminations in polymer matrix composites.« less

Enhanced Cyanate Ester Nanocomposites through Improved Nanoparticle Surface Interactions

DTIC Science & Technology

2013-05-01

and a chemically active 3- aminopropyl surface. The cure behavior and thermal properties of the cyanate ester/modified silica nanocomposites were...area of 150 m 2 /g. Nanoparticles with a chemically active 3- aminopropyl surface were prepared by treating Aerosil 200 particles with 3...however, was visibly observed to severely undercure the nanocomposites with octyl and 3- aminopropyl surface moieties, providing a good initial

Cyanate Ester Resin Modified with Nano-particles for Inclusion in Continuous Fiber Reinforced Composites

DTIC Science & Technology

2011-02-25

custom built rotating oven, to prevent settling during cure. The filler content in the test specimen are verified by thermogravimetric analysis (TGA...using a Shimadzu SA-CP3 centrifugal particle size analyzer. The moisture absorption of the nanoparticles was studied using a Q50 thermogravimetric ...low viscosity bisphenol E cyanate ester resin (BECy) resin reinforced with macro scale carbon fibers and negative CTE nanoparticles . Polymer

Water Uptake Vs. Density and Conversion in Silicon Containing Cyanate Esters (Briefing Charts)

DTIC Science & Technology

2014-12-17

known that cyanate ester networks decrease in density as conversion increases, and that moisture uptake increases as conversion increases at...Charts 3. DATES COVERED (From - To) Dec 2014- Dec 2014 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER In-House Water Uptake Vs. Density and...Polymers and Composites, San Diego, CA, 15 December, 2014. PA#14581 14. ABSTRACT A study was conducted which explored the density, percent water uptake by

Cyanate Ester Resin Modified with Nano-particles for Inclusion in Continuous Fiber Reinforced Composites

DTIC Science & Technology

2011-02-25

thermogravimetric analyzer (TGA) from TA Instruments upon heating at 20 oC/min under air purge. The structural features of the nanoparticles were...low viscosity bisphenol E cyanate ester resin (BECy) resin reinforced with macro scale carbon fibers and negative CTE nanoparticles . Polymer...developed to improve the compatibility of the ZrW2O8 nanoparticles with the polymer matrix. The hybrid composites were prepared with 30 wt

Hydrolytic Network Structure Degradation in Multi-Component Polycyanurate Networks

DTIC Science & Technology

2016-07-28

Approved for Public Release; Distribution Unlimited. PA# 16335 UNCLASSIFIED Cyanate Esters Around the Solar System Images:  courtesy  NASA  (public...release) • The science decks on the Mars Phoenix lander are made from M55J/cyanate ester composites • The solar panel supports on the MESSENGER space...designed by NASA for use as instrument holding structures aboard the James Webb Space Telescope Photo courtesy of  NASA 5Distribution A: Approved for

Phase Separation During the Curing of a Cyanate Ester Oligomer

NASA Astrophysics Data System (ADS)

Gurov, D. A.; Novikov, G. F.

2018-07-01

It is found during the curing of a cyanate ester oligomer that there are such features as a step and a maximum in the frequency dependences (in a range of 10-2-105 Hz) of the real parts of the complex electric conductivity and loss tangent, respectively. In the frequency range where these features are observed, the diagrams of complex electric modulus are semicircles with centers near the abscissas. Subsequent analysis shows these features are due to the formation of the microphase of the intermediate product, carbamate.

Multifunctional Properties of Cyanate Ester Composites with SiO2 Coated Fe3O4 Fillers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Weixing; Sun, Wuzhu; Kessler, Michael R

2013-02-22

SiO2 coated Fe3O4 submicrometer spherical particles (a conducting core/insulating shell configuration) are fabricated using a hydrothermal method and are loaded at 10 and 20 vol % into a bisphenol E cyanate ester matrix for synthesis of multifunctional composites. The dielectric constant of the resulting composites is found to be enhanced over a wide frequency and temperature range while the low dielectric loss tangent of the neat cyanate ester polymer is largely preserved up to 160 ?C due to the insulating SiO2 coating on individual conductive Fe3O4 submicrometer spheres. These composites also demonstrate high dielectric breakdown strengths at room temperature. Dynamicmore » mechanical analysis indicates that the storage modulus of the composite with a 20 vol % filler loading is twice as high as that of neat resin, but the glass transition temperature considerably decreases with increasing filler content. Magnetic measurements reveal a large saturation magnetization and negligibly low coercivity and remanent magnetization in these composites.« less

Influence of Reinforcement Anisotropy on the Stress Distribution in Tension and Shear of a Fusion Magnet Insulation System

NASA Astrophysics Data System (ADS)

Humer, K.; Raff, S.; Prokopec, R.; Weber, H. W.

2008-03-01

A glass fiber reinforced plastic laminate, which consists of half-overlapped wrapped Kapton/R-glass-fiber reinforcing tapes vacuum-pressure impregnated in a cyanate ester/epoxy blend, is proposed as the insulation system for the ITER Toroidal Field coils. In order to assess its mechanical performance under the actual operating conditions, cryogenic (77 K) tensile and interlaminar shear tests were done after irradiation to the ITER design fluence of 1×1022 m-2 (E>0.1 MeV). The data were then used for a Finite Element Method (FEM) stress analysis. We find that the mechanical strength and the fracture behavior as well as the stress distribution and the failure criteria are strongly influenced by the winding direction and the wrapping technique of the reinforcing tapes.

Polytetramethylene glycol-modified polycyanurate matrices reinforced with nanoclays: synthesis and thermomechanical performance

NASA Astrophysics Data System (ADS)

Anthoulis, G. I.; Kontou, E.; Fainleib, A.; Bei, I.

2009-03-01

The outstanding improvement in the physical properties of cyanate esters (CEs) compared with those of competitor resins, such as epoxies, has attracted appreciable attention recently. Cyanate esters undergo thermal polycyclotrimerization to give polycyanurates (PCNs). However, like most thermo setting resins, the main draw back of CEs is brittleness. To over come this disadvan tage, CEs can be toughened by the introduction of polytetramethylene glycol (PTMG), a hydroxyl-terminated polyether. How ever, PTMG has a detrimental impact on Young's modulus. To simultaneously enhance both the ductility and the stiffness of CE, we added PTMG and an organoclay (mont morillonite, MMT) to it. A series of PCN/PTMG/MMT nanocomposites with a constant PTMG weight ratio was pre pared, and the resulting nanophase morphology, i.e., the degree of filler dispersion and distribution in the composite and the thermomechanical properties, in terms of glass-transition behaviour, Young's modulus, tensile strength, and elongation at break, were examined using the scanning elec tron micros copy (SEM), a dynamic mechanical analysis (DMA), and stress-strain measurements, re spectively. It was found that, at a content of MMT below 2 wt.%, MMT nanoparticles were distributed uniformly in the matrix, suggesting a lower degree of agglomeration for these materials. In the glassy state, the significant increase in the storage modulus revealed a great stiffening effect of MMT due to its high Young's modulus. The modification with PTMG led to a 233% greater elongation at break compared with that of neat PCN. The nanocomposites exhibited an invariably higher Young's modulus than PCN/PTMG for all the volume factors of organoclay examined, with the 2 wt.% material displaying the most pronounced in crease in the modulus, in agreement with micros copy results.

A high-performance renewable thermosetting resin derived from eugenol.

PubMed

Harvey, Benjamin G; Sahagun, Christopher M; Guenthner, Andrew J; Groshens, Thomas J; Cambrea, Lee R; Reams, Josiah T; Mabry, Joseph M

2014-07-01

A renewable bisphenol, 4,4'-(butane-1,4-diyl)bis(2-methoxyphenol), was synthesized on a preparative scale by a solvent-free, Ru-catalyzed olefin metathesis coupling reaction of eugenol followed by hydrogenation. After purification, the bisphenol was converted to a new bis(cyanate) ester by standard techniques. The bisphenol and cyanate ester were characterized rigorously by NMR spectroscopy and single-crystal X-ray diffraction studies. After complete cure, the cyanate ester exhibited thermal stability in excess of 350 °C and a glass transition temperature (Tg ) of 186 °C. As a result of the four-carbon chain between the aromatic rings, the thermoset displayed a water uptake of only 1.8% after a four day immersion in 85 °C water. The wet Tg of the material (167 °C) was only 19 °C lower than the dry Tg , and the material showed no significant degradation as a result of the water treatment. These results suggest that this resin is well suited for maritime environments and provide further evidence that full-performance resins can be generated from sustainable feedstocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of Elastic Moduli of Fiber-Resin Composites Using an Impulse Excitation Technique

NASA Technical Reports Server (NTRS)

Viens, Michael J.; Johnson, Jeffrey J.

1996-01-01

The elastic moduli of graphite/epoxy and graphite/cyanate ester composite specimens with various laminate lay-ups was determined using an impulse excitation/acoustic resonance technique and compared to those determined using traditional strain gauge and extensometer techniques. The stiffness results were also compared to those predicted from laminate theory using uniaxial properties. The specimen stiffnesses interrogated ranged from 12 to 30 Msi. The impulse excitation technique was found to be a relatively quick and accurate method for determining elastic moduli with minimal specimen preparation and no requirement for mechanical loading frames. The results of this investigation showed good correlation between the elastic modulus determined using the impulse excitation technique, strain gauge and extensometer techniques, and modulus predicted from laminate theory. The flexural stiffness determined using the impulse excitation was in good agreement with that predicted from laminate theory. The impulse excitation/acoustic resonance interrogation technique has potential as a quality control test.

Mechanisms of Decreased Moisture Uptake in ortho- Methylated Di(Cyanate Esters)

DTIC Science & Technology

2014-10-01

Distribution A: Approved for public release; distribution is unlimited. 1 Mechanisms of Decreased Moisture Uptake in ortho- Methylated Di(Cyanate...when analogous networks containing a single methyl group ortho- to each aryl- cyanurate linkage were prepared by reduction and acid-catalyzed coupling...of salicylic acid followed by treatment with cyanogen bromide and subsequent cyclotrimerization. The differences in water uptake were observed

40 CFR 721.3140 - Vinyl epoxy ester.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Vinyl epoxy ester. 721.3140 Section... Substances § 721.3140 Vinyl epoxy ester. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance vinyl epoxy ester (PMN P-85-527) is subject to reporting under this...

40 CFR 721.3140 - Vinyl epoxy ester.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Vinyl epoxy ester. 721.3140 Section... Substances § 721.3140 Vinyl epoxy ester. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance vinyl epoxy ester (PMN P-85-527) is subject to reporting under this...

40 CFR 721.3140 - Vinyl epoxy ester.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Vinyl epoxy ester. 721.3140 Section... Substances § 721.3140 Vinyl epoxy ester. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance vinyl epoxy ester (PMN P-85-527) is subject to reporting under this...

40 CFR 721.3140 - Vinyl epoxy ester.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Vinyl epoxy ester. 721.3140 Section... Substances § 721.3140 Vinyl epoxy ester. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance vinyl epoxy ester (PMN P-85-527) is subject to reporting under this...

40 CFR 721.3140 - Vinyl epoxy ester.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Vinyl epoxy ester. 721.3140 Section... Substances § 721.3140 Vinyl epoxy ester. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance vinyl epoxy ester (PMN P-85-527) is subject to reporting under this...

Nanoporous Polymer Films of Cyanate Ester Resins Designed by Using Ionic Liquids as Porogens.

PubMed

Fainleib, Alexander; Vashchuk, Alina; Starostenko, Olga; Grigoryeva, Olga; Rogalsky, Sergiy; Nguyen, Thi-Thanh-Tam; Grande, Daniel

2017-12-01

Novel nanoporous film materials of thermostable cyanate ester resins (CERs) were generated by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of varying amounts (from 20 to 40 wt%) of an ionic liquid (IL), i.e., 1-heptylpyridinium tetrafluoroborate, followed by its quantitative extraction after complete CER network formation. The completion of CER formation and IL extraction was assessed using gel fraction content determination, FTIR, 1 H NMR, and energy-dispersive X-ray spectroscopy (EDX). SEM and DSC-based thermoporometry analyses demonstrated the formation of nanoporous structures after IL removal from CER networks, thus showing the effective role of IL as a porogen. Pore sizes varied from ~20 to ~180 nm with an average pore diameter of around 45-60 nm depending on the initial IL content. The thermal stability of nanoporous CER-based films was investigated by thermogravimetric analysis.

Nanoporous Polymer Films of Cyanate Ester Resins Designed by Using Ionic Liquids as Porogens

NASA Astrophysics Data System (ADS)

Fainleib, Alexander; Vashchuk, Alina; Starostenko, Olga; Grigoryeva, Olga; Rogalsky, Sergiy; Nguyen, Thi-Thanh-Tam; Grande, Daniel

2017-02-01

Novel nanoporous film materials of thermostable cyanate ester resins (CERs) were generated by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of varying amounts (from 20 to 40 wt%) of an ionic liquid (IL), i.e., 1-heptylpyridinium tetrafluoroborate, followed by its quantitative extraction after complete CER network formation. The completion of CER formation and IL extraction was assessed using gel fraction content determination, FTIR, 1H NMR, and energy-dispersive X-ray spectroscopy (EDX). SEM and DSC-based thermoporometry analyses demonstrated the formation of nanoporous structures after IL removal from CER networks, thus showing the effective role of IL as a porogen. Pore sizes varied from 20 to 180 nm with an average pore diameter of around 45-60 nm depending on the initial IL content. The thermal stability of nanoporous CER-based films was investigated by thermogravimetric analysis.

Bismaleimide and cyanate ester based sequential interpenetrating polymer networks for high temperature application

NASA Astrophysics Data System (ADS)

Geng, Xing

2005-07-01

A research area of high activity in connection with aerospace engineering has been the development of polymer thermosetting resins that can withstand temperature as high as 300°C while maintaining adequate toughness and providing ease of processing to enable low temperature and low cost composite fabrication methods. In order to meet such requirements, sequential interpenetrating polymer networks (IPNs) based on bismaleimide (BMI) and cyanate ester (CE) monomers were investigated. In these systems, a polycyanurate network is first formed in the presence of BMI and appropriate reactive diluent monomers and, in a second step, a network based on the BMI is created in the presence of a fully formed polycyanurate network. The materials developed can be processed at relatively low temperature (<150°C) and with the aid of electron beam (EB) curing. Of major importance to the success of this work was the identification of a reactive diluent that improves ease of processing and has tailored reactivity to allow for the controlled synthesis of CE-BMI sequential IPNs. Based on solubility and reactivity of a number of reactive diluents, N-acryloylmorpholine (AMP) was selected as a co-monomer for BMI copolymerization. A donor-acceptor reaction mechanism was suggested to explain the relative reactivity of a variety of reactive diluents towards maleimide functionality. The optimum processing parameters for the formation of the first network were determined through the study of metal catalyzed cure and hydrolysis of cyanate esters, whereas the reaction behavior for second network formation in terms of the influence of EB dose rate and temperature was elucidated through an in-situ kinetics study of maleimide and AMP copolymerization. Structure-property relationships were developed which allowed for the design of improved resin systems. In particular, an appropriate network coupler possessing cyanate ester and maleimide functionality was synthesized to link the polycyanurate first network to the BMI/AMP second network and thus form linked sequential IPNs (LIPNs). Consequently, Tg as high as 370°C was achieved and a fracture toughness of 120 J/m2 was obtained for resin systems that possess adequately low viscosity for processing using liquid molding techniques at low temperature.

Injection repair of carbon fiber/bismaleimide composite panels with bisphenol E cyanate ester resin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thunga, Mahendra; Bauer, Amy; Obusek, Kristine

2014-08-01

Resin injection of bisphenol E cyanate ester, a low viscosity resin that cures into a high temperature thermoset polymer, is investigated as a reliable repair method to restore strength and stiffness in delaminated carbon fiber/bismaleimide composites used in aircraft panels. The influence of temperature on the viscosity of the uncured resin was measured to optimize the injection conditions for high resin infiltration into the delaminations. The repair efficiency of the resin was evaluated by varying the panel thickness and the method by which the delamination damage was created in the composite specimens. Ultrasonic scanning (C-scan), flash thermography images, and cross-sectionmore » analysis of repaired panels revealed excellent resin infiltration into the damaged region. Evaluation of mechanical repair efficiency using both bending stiffness and in-plain compressive strength of the composite panels as the repair metrics showed values exceeding 100%.« less

Nanoporous Cyanate Ester Resins: Structure-Gas Transport Property Relationships

NASA Astrophysics Data System (ADS)

Gusakova, Kristina; Fainleib, Alexander; Espuche, Eliane; Grigoryeva, Olga; Starostenko, Olga; Gouanve, Fabrice; Boiteux, Gisèle; Saiter, Jean-Marc; Grande, Daniel

2017-04-01

This contribution addresses the relationships between the structure and gas transport properties of nanoporous thermostable cyanate ester resins (CERs) derived from polycyclotrimerization of 1,1'-bis(4-cyanatophenyl)ethane in the presence of 30 or 50 wt% of inert high-boiling temperature porogens (i.e., dimethyl- or dibutyl phthalates), followed by their quantitative removal. The nanopores in the films obtained were generated via a chemically induced phase separation route with further porogen extraction from the densely crosslinked CERs. To ensure a total desorption of the porogen moieties from the networks, an additional short-term thermal annealing at 250 °C was performed. The structure and morphology of such nanoporous CER-based films were investigated by FTIR and SEM techniques, respectively. Further, the gas transport properties of CER films were analyzed after the different processing steps, and relationships between the material structure and the main gas transport parameters were established.

New materials drive high-performance aircraft

NASA Technical Reports Server (NTRS)

Ruhmann, Douglas C.; Bates, William F., Jr.; Dexter, H. B.; June, Reid B.

1992-01-01

This report shows how advanced composite materials and new processing methods are enabling lighter, lower cost aircraft structures. High-temperature polymers research will focus on systems capable of 50,000 to 100,000 hours of operation in the 212-400 F temperature range. Prospective materials being evaluated include high-temperature epoxies, toughened bismaleimides, cyanates, thermoplastics, polyimides and other polymers.

New Insights into Structure-Property Relationships in Thermosetting Polymers from Studies of Co-Cured Polycyanurate Networks (Preprint)

DTIC Science & Technology

2011-12-19

have shown through positron annihilation studies that a substantial amount of free volume develops during the final stages of cyanate ester cure...Polymers from 5b. GRANT NUMBER Studies of Co-Cured Polycyanurate Networks (preprint) 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Andrew J. Guenthner...Macromolecules. 14. ABSTRACT Studies of the physical properties of the co-cured networks formed from three similar dicyanate ester monomers revealed a

Multifunctional cyanate ester nanocomposites reinforced by hexagonal boron nitride after noncovalent biomimetic functionalization.

PubMed

Wu, Hongchao; Kessler, Michael R

2015-03-18

Boron nitride (BN) reinforced polymer nanocomposites have attracted a growing research interest in the microelectronic industry for their uniquely thermal conductive but electrical insulating properties. To overcome the challenges in surface functionalization, in this study, hexagonal boron nitride (h-BN) nanoparticles were noncovalently modified with polydopamine in a solvent-free aqueous condition. The strong π-π interaction between the hexagonal structural BN and aromatic dopamine molecules facilitated 15 wt % polydopamine encapsulating the nanoparticles. High-performance bisphenol E cyanate ester (BECy) was incorporated by homogeneously dispersed h-BN at different loadings and functionalities to investigate their effects on thermo-mechanical, dynamic-mechanical, and dielectric properties, as well as thermal conductivity. Different theoretical and empirical models were successfully applied to predict thermal and dielectric properties of h-BN/BECy nanocomposites. Overall, the prepared h-BN/BECy nanocomposites exhibited outstanding performance in dimensional stability, dynamic-mechanical properties, and thermal conductivity, together with the controllable dielectric property and preserved thermal stability for high-temperature applications.

Incorporating silica into cyanate ester-based network by sol-gel method: Structure and properties of subnano- and nanocomposites

NASA Astrophysics Data System (ADS)

Bershtein, V.; Fainleib, A.; Kirilenko, D.; Yakushev, P.; Gusakova, K.; Lavrenyuk, N.; Ryzhov, V.

2016-05-01

A series of Cyanate Ester Resins (CER)-based composites containing 0.01-10 wt. % silica, introduced by sol-gel method, was synthesized using tetraethoxysilane (TEOS) and γ-aminopropyltrimethoxysilane (APTMS), and their nanostructure and properties were characterized by means of STEM/EDXS, Far-IR spectroscopy, DMA and DSC methods. It was revealed that the most substantial positive impact on CER dynamics, thermal and mechanical properties is attained at ultra-low silica contents, e.g., at 0.1 wt. % silica where Tg and modulus increase, respectively, by 50° and 60%. In this case, silica nanoclusters are absent in the composite, and only chemically incorporated silica junctions of subnanometric size in the densely-crosslinked CER network could be implied. These composites can be designated as "polymer subnanocomposites". Contrarily, formation of silica nanoclusters and especially their aggregates of hundreds nanometers in size at silica contents of 2-10 wt. % led to the distinct negative impact on the matrix properties.

Long Focal Length Large Mirror Fabrication System

NASA Technical Reports Server (NTRS)

Bennett, H. E.

2003-01-01

The goals of this ambitious program are (1) to develop systems to make large superpolished optical mirrors, (2) to develop low scatter polishing techniques using centrifugal elutriation, (3) to develop a means of measuring scatter at any point on the mirror, (4) to polish a Hindle sphere to measure the optical figure of a one meter diameter convex mandrel, and (5) to fabricate low scatter, large adaptive optic graphite filled, cyanate ester replica transfer mirrors using these mandrels. Deliverables are a 30 cm diameter superpolished composite AO mirror. We fabricated a 1/3rd meter superpolished zerodur flat mandrel and with the support of our major subcontractor, Composite Mirror Applications Inc (CMA) we have demonstrated a 30 cm lightweight cyanate ester mirror with an rms microroughness between 0.6 and 0.8 nm and 8 faceplate influence function of 5 cm. The influence function was chosen to be comparable to the atmospheric correlation coefficient r(sub 0) which is about 5 cm at sea level. There was no print-thru of the graphite fibers in the cyanate ester surface (the bane of many previous efforts to use cyanate ester mirrors). Our subcontractor has devised a means for developing a 30-50 nm thick layer of graphite free pure ester resin on the surface of the mirrors. This graphite fiber filled material has a thermal expansion coefficient in the 10(exp -8) centimeter per Kelvin range (the same range of expansion coefficient as Zerodur and ULE glasses) and does not take up water and swell, so it is a nearly ideal mirror material in these areas. Unfortunately for these 0.8mm thick faceplates, the number of plies is not enough to result in isometric coverage. Isolated figure irregularities can appear, making it necessary to go to thicker faceplates. The influence function will then only approximate the length of r(sub 0), at higher altitudes or longer wavelengths. The influence function goes as the cube of the thickness, so we are now making a faceplate optimized for an infrared wavelength, possibly that used for the AO system of the Keck telescope, instead of 0.63 microns. We have polished a 55 cm diameter mandrel to better than 1/20th wave optical figure in the visible using centrifugal elutriation. CMA has just told us that it needs to retool to get optimum mirror faceplate quality in this size, so implementing the 55 cm AO mirror may be delayed somewhat. We expect to complete our 1/3 rd meter AO mirror on time using novel piezoelectric actuators with a throw of one micrometer per volt, as compared to 0.005 micrometers per volt for conventional piezoelectric actuators. We will then demonstrate its AO performance interferometrically.

Mechanical Characterization of the Iter Mock-Up Insulation after Reactor Irradiation

NASA Astrophysics Data System (ADS)

Prokopec, R.; Humer, K.; Fillunger, H.; Maix, R. K.; Weber, H. W.

2010-04-01

The ITER mock-up project was launched in order to demonstrate the feasibility of an industrial impregnation process using the new cyanate ester/epoxy blend. The mock-up simulates the TF winding pack cross section by a stainless steel structure with the same dimensions as the TF winding pack at a length of 1 m. It consists of 7 plates simulating the double pancakes, each of them is wrapped with glass fiber/Kapton sandwich tapes. After stacking the 7 plates, additional insulation layers are wrapped to simulate the ground insulation. This paper presents the results of the mechanical quality tests on the mock-up pancake insulation. Tensile and short beam shear specimens were cut from the plates extracted from the mock-up and tested at 77 K using a servo-hydraulic material testing device. All tests were repeated after reactor irradiation to a fast neutron fluence of 1×1022 m-2 (E>0.1 MeV). In order to simulate the pulsed operation of ITER, tension-tension fatigue measurements were performed in the load controlled mode. Initial results show a high mechanical strength as expected from the high number of thin glass fiber layers, and an excellent homogeneity of the material.

Iron-catalyzed regio- and stereoselective substitution of gamma,delta-epoxy-alpha,beta-unsaturated esters and amides with Grignard reagents.

PubMed

Hata, Takeshi; Bannai, Rie; Otsuki, Mamoru; Urabe, Hirokazu

2010-03-05

When gamma,delta-epoxy-alpha,beta-unsaturated esters or amides were treated with 2 equiv of Grignard reagents in the presence of 10-24 mol % FeCl(2), regio- and stereoselective substitution of the epoxide moiety with the Grignard reagent occurred to give exclusively delta-hydroxy-gamma-alkyl or aryl-alpha,beta-unsaturated esters or amides in good yields.

Feasibility study on the development of tough, moisture-resistant laminating resins

NASA Technical Reports Server (NTRS)

Brand, R. A.; Harrison, E. S.

1979-01-01

The potential of cyanate resins as replacement for epoxy resins in composites with graphite fiber reinforcement was investigated in an effort to provide improved moisture resistance and toughness in laminating systems at a projected cost, handleability, and processing requirements equivalent to 400 K (260 F) curing epoxies. Monomer synthesis, formulation, blending, resin preparation, catalysis studies, prepreg preparation, laminate fabrication, and testing are discussed. A graphite fiber reinforced laminate was developed with 95 percent retention of the original 363 K (180 F) flexural strength and 70 percent retention of the 363 K (180 F) short beam shear strength after 500 hour exposure to 95 + 7 relative humidity at 324 K (120 F).

Silicon-Containing Tri- and Tetra-Functional Cyanate Esters: Synthesis, Cure Kinetics, and Network Properties

DTIC Science & Technology

2014-01-01

24. Pollack, S. K.; Fu, Z. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1998, 39, 452-453. 25. Devaraju, S.; Vengatesan, M. R.; Selvi , M...Ganguli, S.; Dean, D.; Jordan, K.; Price, G.; Vaia, R. Polymer 2003, 44, 1315-1319. 54. Devaraju, S.; Vengatesan, M. R.; Selvi , M.; Kumar, A. A

Structure Property Relationships of Biobased Epoxy Resins

NASA Astrophysics Data System (ADS)

Maiorana, Anthony Surraht

The thesis is about the synthesis, characterization, development, and application of epoxy resins derived from sustainable feedstocks such as lingo-cellulose, plant oils, and other non-food feedstocks. The thesis can be divided into two main topics 1) the synthesis and structure property relationship investigation of new biobased epoxy resin families and 2) mixing epoxy resins with reactive diluents, nanoparticles, toughening agents, and understanding co-curing reactions, filler/matrix interactions, and cured epoxy resin thermomechanical, viscoelastic, and dielectric properties. The thesis seeks to bridge the gap between new epoxy resin development, application for composites and advanced materials, processing and manufacturing, and end of life of thermoset polymers. The structures of uncured epoxy resins are characterized through traditional small molecule techniques such as nuclear magnetic resonance, high resolution mass spectrometry, and infrared spectroscopy. The structure of epoxy resin monomers are further understood through the process of curing the resins and cured resins' properties through rheology, chemorheology, dynamic mechanical analysis, tensile testing, fracture toughness, differential scanning calorimetry, scanning electron microscopy, thermogravimetric analysis, and notched izod impact testing. It was found that diphenolate esters are viable alternatives to bisphenol A and that the structure of the ester side chain can have signifi-cant effects on monomer viscosity. The structure of the cured diphenolate based epoxy resins also influence glass transition temperature and dielectric properties. Incorporation of reactive diluents and flexible resins can lower viscosity, extend gel time, and enable processing of high filler content composites and increase fracture toughness. Incorpora-tion of high elastic modulus nanoparticles such as graphene can provide increases in physical properties such as elastic modulus and fracture toughness. The synthesis of epoxy resins with aliphatic esters in the main chain of the polymer allow for chemical recycling under alkaline conditions and changing the hydrophobicity and access of main chain esters influences the rate of polymer degradation. The thesis further provides strategies and concepts that will allow for future researchers to rapidly understand how to manipulate epoxy resins for specific end uses and supplements current understanding of epoxy curing agents, accelerators, and interactions with fillers.

Graphene Oxide and Thermally Exfoliated Graphene Cyanate Ester Resin Composites

DTIC Science & Technology

2013-05-01

solution was cooled to 0 °C by placing the flask in an ice bath and 30 g of potassium permanganate was added slowly with stirring which caused the...suspension to turn to a thick paste. After the addition of potassium permanganate the solution was warmed to 35 °C and allowed to stir for 30 minutes. After

Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin

NASA Astrophysics Data System (ADS)

Chuang, Wang; Geng-sheng, Jiao; Lei, Peng; Bao-lin, Zhu; Ke-zhi, Li; Jun-long, Wang

2018-06-01

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2 and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were investigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding between nano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the 3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25% compared with that of the pure CE, and the wear resistance increased by 77%.

Predictive Methods for Dense Polymer Networks: Combating Bias with Bio-Based Structures

DTIC Science & Technology

2016-03-16

Informatics Tools Acknowledgements: Air Force Office of Scientific Research, Air Force Research Laboratory, Office of Naval Research, Strategic...Sources and Methods • Bio-based cyanate esters have been made from anethole, resveratrol, eugenol, cresol, lignin, vanillin, and even creosote oils ...not large by informatics standards, it nonetheless represents a significant amount of synthetic effort. Because the data is limited, minimizing

A Preliminary Investigation of the E-Beam Induced Polymerization of Maleimide and Norbornene End-capped Polyimides

NASA Technical Reports Server (NTRS)

Palmese, Giuseppe R.; Meador, Michael A. (Technical Monitor)

2005-01-01

A research area of high activity in connection with aerospace engineering has been the development of polymer thermosetting resins that can resist temperature as high as 300 C while maintaining adequate toughness, and providing ease of processing to enable low temperature and low cost composite fabrication methods. In order to meet such requirements, sequential interpenetrating polymer networks (IPNs) based on bismaleimide (BMI) and cyanate ester (CE) monomers were investigated. In these systems, a polycyanurate network is first formed in the presence of BMI and appropriate reactive diluent monomers and in a second step, a network based on the BMI is created in the presence of a fully formed polycyanurate network. The materials developed can be processed at relatively low temperature (less than 150 C) and with the aid of electron beam (EB) curing. Of major importance to the success of this work was the identification of a reactive diluent that improves ease of processing and has tailored reactivity to allow for the controlled synthesis of CE-BMI sequential IPNs. Based on solubility and reactivity of a number of reactive diluents, N-acryloylmorpholine (AMP) was selected as a comonomer for BMI copolymerization. A donor-acceptoreaction mechanism was suggested to explain the relative reactivity of a variety of reactive diluents towards maleimide functionality. The optimum processing parameters for the formation of the first network were determined through the study of metal catalyzed cure and hydrolysis of cyanate esters, whereas the reaction behavior for second network formation in terms of the influence of EB dose rate and temperature was elucidated through an in-situ kinetics study of maleimide and AMP copolymerization. Structure-property relationships were developed which allowed for the design of improved resin systems. In particular, appropriate network coupler possessing cyanate ester and maleimide functionality was synthesized to link the polycyanurate first network to the BMI/AMP second network and thus form linked sequential IPNs (LIPNs). Consequently, Tg as high as 370 C was achieved and a fracture toughness of 120 Joules per square meters was obtained for resin systems that possess adequately low viscosity for processing using liquid molding techniques at low temperature.

Environmentally Benign Repair of Composites Using High Temperature Cyanate Ester Nanocomposites

DTIC Science & Technology

2010-10-01

temperature by magnetic stirring. Thermogravimetric analysis (TG) measurements were performed on a TG model Q50 (TA Instruments, Inc.) to determine the...standard 1259-85. These experiments were also compared with thermogravimetric analysis (TGA) in both dynamic heating and isothermal conditions. The...characterized with thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). For the TG, about 20 mg of sample was placed in

Organic Crystal Engineering of Thermosetting Cyanate Ester Monomers: Influence of Structure on Melting Point

DTIC Science & Technology

2016-05-27

often discussed in the field of thermosetting materials, crystal engineering1-4 plays a key role in facilitating the successful utilization of these...not to alter the desirable properties of the polymerized networks. Fortunately, the field of crystal engineering provides examples where even very...Chickos and Acree.26 For molecular modeling, methods ranging from atomistic simulations with semi-empirical force fields to density functional

Photoresponsive liquid crystalline epoxy networks with shape memory behavior and dynamic ester bonds

DOE PAGES

Rios, Orlando; Chen, Jihua; Li, Yuzhan; ...

2016-06-01

Functional polymers are intelligent materials that can respond to a variety of external stimuli. However, these materials have not yet found widespread real world applications because of the difficulties in fabrication and the limited number of functional building blocks that can be incorporated into a material. Here, we demonstrate a simple route to incorporate three functional building blocks (azobenzene chromophores, liquid crystals, and dynamic covalent bonds) into an epoxy-based liquid crystalline network (LCN), in which an azobenzene-based epoxy monomer is polymerized with an aliphatic dicarboxylic acid to create exchangeable ester bonds that can be thermally activated. Lastly, all three functionalmore » building blocks exhibited good compatibility, and the resulting materials exhibits various photomechanical, shape memory, and self-healing properties because of the azobenzene molecules, liquid crystals, and dynamic ester bonds, respectively.« less

New and Simple Ways to Minimize Water Uptake and Hydrolytic Degradation in Cyanate Esters

DTIC Science & Technology

2016-01-27

Photo by U.S. Navy photo by Photographer’s Mate 1st Class Anibal Rivera (public domain). Importance of Moisture Uptake in Composite Component... Moisture Uptake in Thermoset Resins • Increasing conversion joins together more "loose ends" in the network, eliminating free space where water can be...public release; distribution is unlimited. PA Clearance #16205 6 Proposed Role of Vitrification in Controlling Moisture Uptake • Increasing conversions

Curing of a Bisphenol-E Based Cyanate Ester using Magnetic Nanoparticles as an Internal Heat Source through Induction Heating

DTIC Science & Technology

2013-11-01

magnetic field as a heat source for the polymerization avoids some of these difficulties. EXPERIMENTAL SECTION Iron (III) chloride hexahydrate (ACS...reagent, 97%), iron (II) chloride tetrahydrate (ReagentPlus®, 98%), tetramethylammonium hydroxide solution (25 wt. % in water), and oleic acid (technical...Edwards Air Force Base and used without further purification. Preparation of Iron Oxide Magnetic Nanoparticles.51 Iron (III) chloride hexahydrate (11.75

Formulation and Physical Properties of Cyanate Ester Nanocomposites Based on Graphene

DTIC Science & Technology

2014-03-01

during cure. The addition of GO, and, to a lesser extent, TRGO, resulted in improved mechanical properties, particularly fracture toughness, with the...a lesser extent, TRGO, resulted in improved mechanical proper- ties, particularly fracture toughness, with the addition of TRGO having a modestly...LECy. However, the mechanism of fracture toughness improvement may be different with each form of graphene. In the case of GO, the high degree of oxi

Development of tough, moisture resistant laminating resins

NASA Technical Reports Server (NTRS)

Brand, R. A.; Harrison, E. S.

1982-01-01

Tough, moisture resistant laminating resins for employment with graphite fibers were developed. The new laminating resins exhibited cost, handleability and processing characteristics equivalent to 394K (250 F) curing epoxies. The laminating resins were based on bisphenol A dicyanate and monofunctional cyanates with hydrophobic substituents. These resins sorb only small quantities of moisture at equilibrium (0.5% or less) with minimal glass transition temperature depression and represent an improvement over epoxies which sorb around 2% moisture at equilibrium. Toughening was accomplished by the precipitation of small diameter particles of butadiene nitrile rubber throughout the resin matrix. The rubber domains act as microcrack termini and energy dissipation sites, allowing increased stress accommodation prior to catastrophic failure. A unique blend of amine terminated butadiene nitrile elastomer (MW 2,000) and a high nitrile content butadiene nitrile rubber yielded the desired resin morphology.

Radiation Shielding Study of Advanced Data and Power Management Systems (ADPMS) Housing Using Geant4

NASA Astrophysics Data System (ADS)

Garcia, F.; Kurvinen, K.; Brander, T.; Orava, R.; Heino, J.; Virtanen, A.; Kettunen, H.; Tenhunen, M.

2008-02-01

A design goal for current space system is to reduce the mass used to enclose components of the spacecraft. One potential target is to reduce the mass of electronics and its housings. The use of composite materials, especially CFRP (Carbon Fiber Reinforced Plastic) is a well known and vastly used approach to mass reduction. A design goal, cost reduction, has increased the use of commercial (non-space qualified) electronics. These commercial circuits and other components cannot tolerate as high radiation levels as space qualified components. Therefore, the use of standard electronics components poses a challenge in terms of the radiation protection capability of the ADPMS housings. The main goal of this study is to provide insight on the radiation shielding protection produced by different configurations of CFRP tungsten laminates of epoxies and cyanate esters and then to compare them to the protection given by the commonly used aluminum. For a spacecraft operating in LEO and MEO orbits the main components of the space radiation environment are energetic electrons and protons, therefore in our study we will compare the experimental and simulation results of the radiation attenuation of different types of laminates for those particles. At the same time the experimental data has been used to validate the Geant4 model of the laminates, which can be used for future optimizations of the laminate structures.

A New Silicon-Containing Bis(Cyanate) Ester Resin with Improved Thermal Oxidation and Moisture Resistance

DTIC Science & Technology

2006-05-23

making it an ideal comparative material. Scheme 1 BnO Br Si R R OYYO Si R R NCO OCN 1. n- BuLi THF/-78 oC 2. Me2SiCl2 1; R = Me, Y= Bn H2...carbonate in DMF) was treated with n- BuLi (15.2 mL, 38 mmol) and allowed to react with stirring for 30 min. This mixture, now heterogeneous, was

Interactions Between Structure and Processing that Control Moisture Uptake in High-Performance Polycyanurates (Briefing Charts)

DTIC Science & Technology

2015-03-24

distribution is unlimited.  . Interactions Between Structure and Processing that Control Moisture Uptake in High-Performance Polycyanurates Presenter: Dr...Edwards AFB, CA 4 California State University, Long Beach, CA 90840 2 Outline: Basic Studies of Moisture Uptake in Cyanate Ester Networks • Background...Motivation • SOTA Theories of Moisture Uptake in Thermosetting Networks • New Tools and New Discoveries • Unresolved Issues and Ways to Address Them

High-k 3D-barium titanate foam/phenolphthalein poly(ether sulfone)/cyanate ester composites with frequency-stable dielectric properties and extremely low dielectric loss under reduced concentration of ceramics

NASA Astrophysics Data System (ADS)

Zheng, Longhui; Yuan, Li; Guan, Qingbao; Liang, Guozheng; Gu, Aijuan

2018-01-01

Higher dielectric constant, lower dielectric loss and better frequency stability have been the developing trends for high dielectric constant (high-k) materials. Herein, new composites have been developed through building unique structure by using hyperbranched polysiloxane modified 3D-barium titanate foam (BTF) (BTF@HSi) as the functional fillers and phenolphthalein poly(ether sulfone) (cPES)/cyanate ester (CE) blend as the resin matrix. For BTF@HSi/cPES/CE composite with 34.1 vol% BTF, its dielectric constant at 100 Hz is as high as 162 and dielectric loss is only 0.007; moreover, the dielectric properties of BTF@HSi/cPES/CE composites exhibit excellent frequency stability. To reveal the mechanism behind these attractive performances of BTF@HSi/cPES/CE composites, three kinds of composites (BTF/CE, BTF/cPES/CE, BTF@HSi/CE) were prepared, their structure and integrated performances were intensively investigated and compared with those of BTF@HSi/cPES/CE composites. Results show that the surface modification of BTF is good for preparing composites with improved thermal stability; while introducing flexible cPES to CE is beneficial to fabricate composites with good quality through effectively blocking cracks caused by the stress concentration, and then endowing the composites with good dielectric properties at reduced concentration of ceramics.

Effect of side-chain structure of rigid polyimide dispersant on mechanical properties of single-walled carbon nanotube/cyanate ester composite.

PubMed

Yuan, Wei; Li, Weifeng; Mu, Yuguang; Chan-Park, Mary B

2011-05-01

Three kinds of polymer, polyimide without side-chain (PI), polyimide-graft-glyceryl 4-nonylphenyl ether (PI-GNE), and polyimide-graft-bisphenol A diglyceryl acrylate (PI-BDA), have been synthesized and used to disperse single-walled carbon nanotubes (SWNTs) and to improve the interfacial bonding between SWNTs and cyanate ester (CE) matrix. Visual observation, UV-vis-near-IR (UV-vis-NIR) spectra, and atomic force microscopy (AFM) images show that both PI-GNE and PI-BDA are highly effective at dispersing and debundling SWNTs in DMF, whereas PI is less effective. Interaction between SWNTs and PI, PI-GNE or PI-BDA was confirmed by computer simulation and Raman spectra. A series of CE-based composite films reinforced with different loadings of SWNTs, SWNTs/PI, SWNTs/PI-GNE and SWNTs/PI-BDA were prepared by solution casting. It was found that, because of the unique side-chain structure of PI-BDA, SWNTs/PI-BDA disperse better in CE matrix than do SWNTs/PI-GNE, SWNTs/PI, and SWNTs. As a result, SWNTs/PI-BDA/CE composites have the greatest improvement in mechanical properties of the materials tested. These results imply that the choice of side-chain on a dispersant is very important to the dispersion of SWNTs in matrix and the filler/matrix interfacial adhesion, which are two key requirements for achieving effective reinforcement.

Design Guide: Designing and Building High Voltage Power Supplies. Volume 2

DTIC Science & Technology

1988-08-01

and edges. * Isolation system: * One layer ol’ Tedlar: or type 120 glass fabric with a compatible resin : or finish. 199 5.4.2 Composite Joints...plastics Cellulose esters Asphalt Cork Chloride flux Epoxy resins Copper (bare) Masonite Fiber board Melamine resins Greases Nylon Polyvinyl chloride resins ...cycloaliphatic epoxy to a level inferior to the porcelain. In one application having a glass -cloth epoxy- based laminate coated with cycloaliphatic epoxy the

Glass Transition Temperature Measurement for Undercured Cyanate Ester Networks: Challenges, Tips, and Tricks (Briefing Charts)

DTIC Science & Technology

2014-01-29

DISTRIBUTION A: Approved for public release; distribution is unlimited. Thermosetting Polymers Have a TG Envelope – Not Just a TG 4 • The glass transition...glass transition temperature of a thermosetting polymer can vary over a wide range of temperatures depending on how the polymer is processed • A... thermosetting polymer with only one kind of network formation and negligible side reactions, the conversion may be determined at every point in the scan. • By

New Approaches to Maximizing Thermo-oxidation Resistance of Polycyanurate Networks

DTIC Science & Technology

2014-08-13

Resveratrol -based CE Delivers Exceptional Thermal Stability and Fire Resistance Acknowledgements: Strategic Environmental Research and Development...CH2-CH2- (dihydro resveratrol ) OH OH HO R OCN OCN NCO R Char (65%) Cure at 250C N N N N N N O O O R N N N Resveratrol cyanate ester* Resveratrol ...triazine thermoset resin > 450C Fire ( resveratrol ) • Polyphenolic antioxidant used as a dietary supplement • Extracted from seaweed, red grapes, red wine

Ionic Liquid-Modified Thermosets and Their Nanocomposites: Dispersion, Exfoliation, Degradation, and Cure

NASA Astrophysics Data System (ADS)

Throckmorton, James A.

This dissertation explores the application of a room temperature ionic liquid (RTIL) to problems in the chemistry, processing, and modification of thermosetting polymers. In particular, the solution properties and reaction chemistry of 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-DCN) are applied to problems of nanoparticle dispersion and processing, graphite exfoliation, cyanate ester (CE) cure, and the environmental degradation of CEs. Nanoparticle Dispersion: Nanocomposite processing can be simplified by using the same compound as both a nanoparticle solvent and an initiator for polymerization. This dual-function molecule can be designed both for solvent potential and reaction chemistry. EMIM-DCN, previously shown by our lab to act as an epoxy initiator, is used in the synthesis of silica and acid expanded graphite composites. These composites are then characterized for particle dispersion and physical properties. Individual particle dispersion of silica nanocomposites is shown, and silica nanocomposites at low loading show individual particle dispersion and improved modulus and fracture toughness. GNP nanocomposites show a 70% increase in modulus along with a 10-order of magnitude increase in electrical conductivity at 6.5 vol%, and an electrical percolation threshold of 1.7 vol%. Direct Graphite Exfoliation By Laminar Shear: This work presents a laminar-shear alternative to chemical processing and chaotic flow-fields for the direct exfoliation of graphite and the single-pot preparation of nanocomposites. Additionally, we develop the theory of laminar flow through a 3-roll mill, and apply that theory to the latest developments in the theory of graphite interlayer shear. The resulting nanocomposite shows low electrical percolation (0.5 vol%) and low thickness (1-3 layer) graphite/graphene flakes. Additionally, the effect of processing conditions by rheometry and comparison with solvent-free conditions reveal the interactions between processing and matrix properties and provide insight into the theory of the chemical and physical exfoliation of graphite crystals and the resulting polymer matrix dispersion. Cyanate Ester Cure: Dicyanamide-containing ionic liquids decrease the cure temperature of bi- and tri-functional CEs. During the cure reaction, the dicyanamide anion completely reacts and is incorporated into the triazine network. The cure effect was found in many dicyanamide-containing ionic liquids with diverse cations. This invention creates a novel, ionic thermoset polymer. The dicyanamide initiator provides an alternative to metal and hydroxyl catalysts (which have been shown to accelerate degradation and possess human and environmental toxicity). Additionally, the ionic character of the new polymer, rare among thermosets, lends itself to future research and novel applications. RTIL initiation also paves the way to new CE technologies, including RTIL-CE nanocomposites, prepared by graphite exfoliation and nanocomposite dispersion techniques developed herin.

Properties of radiation stable insulation composites for fusion magnet

NASA Astrophysics Data System (ADS)

Wu, Zhixiong; Huang, Rongjin; Huang, Chuanjun; Li, Laifeng

2017-09-01

High field superconducting magnets made of Nb3Al will be a suitable candidate for future fusion device which can provide magnetic field over 15T without critical current degradation caused by strain. The higher magnetic field and the larger current will produce a huge electromagnetic force. Therefore, it is necessary to develop high strength cryogenic structural materials and electrical insulation materials with excellent performance. On the other hand, superconducting magnets in fusion devices will experience significant nuclear radiation exposure during service. While typical structural materials like stainless steel and titanium have proven their ability to withstand these conditions, electrical insulation materials used in these coils have not fared as well. In fact, recent investigations have shown that electrical insulation breakdown is a limiting factor in the performance of high field magnets. The insulation materials used in the high field fusion magnets should be characterized by excellent mechanical properties, high radiation resistivity and good thermal conductivity. To meet these objectives, we designed various insulation materials based on epoxy resins and cyanate ester resins and investigated their processing characteristic and mechanical properties before and after irradiation at low temperature. In this paper, the recent progress of the radiation stable insulation composites for high field fusion magnet is presented. The materials have been irradiated by 60Co γ-ray irradiation in air at ambient temperature with a dose rate of 300 Gy/min. The total doses of 1 MGy, 5 MGy and 10 MGy were selected to the test specimens.

A New Epoxy Bis-Phosphonate Crosslinker for Durable Fire Retardancy on Cotton

USDA-ARS?s Scientific Manuscript database

A new epoxy bis-phosphonate crosslinker for cotton [2-(dimethoxy-phosphorylmethyl)-oxiranylmethyl]-phosphonic acid dimethyl ester was prepared in two steps from 3-chloro-2-chloromethylpropene in 55% yield. The new monomer was characterized by proton and carbon NMR and GC-mass spectrometry. This cro...

Epoxy Phosphonate Crosslinkers for Providing Flame Resistance to Cotton Textiles

USDA-ARS?s Scientific Manuscript database

Two new monomers (2-methyl-oxiranylmethyl)-phosphonic acid dimethyl ester (3) and [2-(dimethoxy-phosphorylmethyl)-oxyranylmethyl]-phosphonic acid dimethyl ester (6) were prepared and used with dicyandiamide (7) and citric acid (8) to impart flame resistance to cotton plain weave, twill, and 80:20-co...

Thermosets of epoxy monomer from Tung oil fatty acids cured in two synergistic ways

USDA-ARS?s Scientific Manuscript database

A new epoxy monomer from tung oil fatty acids, glycidyl ester of eleostearic acid (GEEA), was synthesized and characterized by 1H-NMR and 13C-NMR spectroscopy. Differential scanning calorimetry analysis (DSC) and FT-IR were utilized to investigate the curing process of GEEA cured by both dienophiles...

Synthesis and characterization of estolide esters containing epoxy and cyclic carbonate groups

USDA-ARS?s Scientific Manuscript database

The unsaturated sites in oleic 2-ethylhexyl estolide esters (containing 35% monoenic fatty acids) were converted into epoxide and five-membered cyclic carbonate groups and the products characterized by Fourier transform infrared spectra (FTIR), 1H-, and 13C-nuclear magnetic resonance (NMR) spectrosc...

A Novel Anoxic Pathway for Urea and Cyanate in Marine Oxygen Deficient Zones Revealed by Combined Microbiological and Biogeochemical Tools

NASA Astrophysics Data System (ADS)

Widner, B.; Fuchsman, C. A.; Babbin, A. R.; Ji, Q.; Mulholland, M. R.

2016-02-01

Urea and cyanate are reduced nitrogen compounds that can serve as nitrogen and carbon sources for marine microbes, and cyanate forms from decomposition of urea. Some marine bacteria, including cyanobacteria, possess genes encoding an ABC-type cyanate transporter and an intracellular cyanate hydratase, and genes for urea uptake and assimilation are widespread. To investigate cyanate distribution and availability in the ocean, we recently developed a nanomolar cyanate assay specific to seawater. In an oxygenated water column, urea and cyanate concentrations are generally low in surface waters and exhibit a concentration maximum near the base of the euphotic zone likely due to production from organic matter degradation. Below the euphotic zone, urea and cyanate concentrations decrease, likely due to oxidation reactions. It has been suggested that simple organic nitrogen compounds may support anaerobic ammonium oxidation (anammox) in oxygen deficient zones (ODZs). We mapped urea and cyanate distributions and used stable isotope-labeled urea and cyanate to measure their potential support of anammox and their uptake within the Eastern Tropical North and South Pacific ODZs. We also employed metagenomic techniques to determine the abundance and distribution of genes for the uptake and assimilation of urea and cyanate. The combined data indicate that, in ODZs, urea is used primarily as a nitrogen source while cyanate is used as both a nitrogen source and to generate energy.

Epoxy monomers derived from tung oil fatty acids and its regulable thermosets cured in two synergistic ways

USDA-ARS?s Scientific Manuscript database

A new bio-based epoxy monomer with conjugated double bonds, glycidyl ester of eleostearic acid (GEEA), was synthesized from tung oil fatty acids and characterized by 1H-NMR, 13C-NMR and Mass Spectrometry Analysis (MSA). Differential Scanning Calorimetry (DSC) analysis and FT-IR were utilized to inve...

An epoxy monomer derived from Tung oil fatty acids and its products cured by two synergistic reactions

USDA-ARS?s Scientific Manuscript database

A new bio-based epoxy monomer containing conjugated double bonds, the glycidyl ester of eleostearic acid (GEEA), was synthesized from tung oil fatty acids. It was characterized using 1H-NMR, 13C-NMR and mass spectrometric analysis. Differential scanning calorimetry (DSC) and FT-IR spectroscopy were ...

Bio-Based Nanocomposites: An Alternative to Traditional Composites

ERIC Educational Resources Information Center

Tate, Jitendra S.; Akinola, Adekunle T.; Kabakov, Dmitri

2009-01-01

Polymer matrix composites (PMC), often referred to as fiber reinforced plastics (FRP), consist of fiber reinforcement (E-glass, S2-glass, aramid, carbon, or natural fibers) and polymer matrix/resin (polyester, vinyl ester, polyurethane, phenolic, and epoxies). Eglass/ polyester and E-glass/vinyl ester composites are extensively used in the marine,…

Analysis of palmitoyl apo-astaxanthinals, apo-astaxanthinones, and their epoxides by UHPLC-PDA-ESI-MS.

PubMed

Weesepoel, Yannick; Gruppen, Harry; de Bruijn, Wouter; Vincken, Jean-Paul

2014-10-22

Food products enriched with fatty acid-esterified xanthophylls may result in deviating dietary apo-carotenoids. Therefore, free astaxanthin and its mono- and dipalmitate esters were subjected to two degradation processes in a methanolic model system: light-accelerated autoxidation and hypochlorous acid/hypochlorite (HOCl/OCl(-)) bleaching. Reversed phase ultrahigh-performance liquid chromatography photodiode array with in-line electrospray ionization mass spectrometry (RP-UHPLC-PDA-ESI-MS) was used for assessment of degradation products. Apo-astaxanthinals and -astaxanthinones containing 3 (apo-9) to 10 (apo-8') conjugated double bonds were found upon autoxidation for all three types of astaxanthin (except free apo-8'-astaxanthinal). Fragmentation of [M + H](+) and [M + Na](+) parent masses of apo-astaxanthins from dipalmitate astaxanthin indicated palmitate esterification. Astaxanthin monopalmitate degradation resulted in a mixture of free and palmitate apo-astaxanthins. HOCl/OCl(-) rapidly converted the astaxanthins into a mixture of epoxy-apo-9- and epoxy-apo-13-astaxanthinones. The palmitate ester bond was hardly affected by autoxidation, whereas for HOCl/OCl(-) the ester bond of the apo-astaxanthin palmitoyl esters was degraded.

Ames Infusion Stories for NASA Annual Technology Report: Development of an Ablative 3D Quartz / Cyanate Ester Composite Multi-Functional Material for the Orion Spacecraft Compression Pad

NASA Technical Reports Server (NTRS)

Smith, Brandon; Jan, Darrell Leslie; Venkatapathy, Ethiraj

2015-01-01

Vehicles re-entering Earth's atmosphere require protection from the heat of atmospheric friction. The Orion Multi-Purpose Crew Vehicle (MPCV) has more demanding thermal protection system (TPS) requirements than the Low Earth Orbit (LEO) missions, especially in regions where the structural load passes through. The use of 2-dimensional laminate materials along with a metal insert, used in EFT1 flight test for the compression pad region, are deemed adequate but cannot be extended for Lunar return missions.

Thermal-mechanical behavior of high precision composite mirrors

NASA Technical Reports Server (NTRS)

Kuo, C. P.; Lou, M. C.; Rapp, D.

1993-01-01

Composite mirror panels were designed, constructed, analyzed, and tested in the framework of a NASA precision segmented reflector task. The deformations of the reflector surface during the exposure to space enviroments were predicted using a finite element model. The composite mirror panels have graphite-epoxy or graphite-cyanate facesheets, separated by an aluminum or a composite honeycomb core. It is pointed out that in order to carry out detailed modeling of composite mirrors with high accuracy, it is necessary to have temperature dependent properties of the materials involved and the type and magnitude of manufacturing errors and material nonuniformities. The structural modeling and analysis efforts addressed the impact of key design and materials parameters on the performance of mirrors.

Cyanate ester-nanoparticle composites as multifunctional structural capacitors

NASA Astrophysics Data System (ADS)

De Leon, J. Eliseo

An important goal of engineering is to increase the energy density of electrical energy storage devices used to deliver power onboard mobile platforms. Equally important is the goal to reduce the overall mass of the vehicles transporting these devices to achieve increased fuel and cost efficiency. One approach to meeting both these objectives is to develop multifunctional systems that serve as both energy storage and load bearing structural devices. Multifunctional devices consist of constituents that individually perform a subset of the overall desired functions. However, the synergy achieved by the combination of each constituent's characteristics allows for system-level benefits that cannot be achieved by simply optimizing the separate subsystems. We investigated multifunctional systems consisting of light weight polymer matrix and high dielectric constant fillers to achieve these objectives. The monomer of bisphenol E cyanate ester exhibited excellent processing ability because of its low room temperature viscosity. Additionally, the fully cured thermoset demonstrated excellent thermal stability, specific strength and stiffness. Fillers, including multi-walled carbon nanotubes, nanometer scale barium titanate and nanometer scale calcium copper titanate, offer high dielectric constants that raised the effective dielectric constant of the polymer matrix composite. The combination of high epsilon'and high dielectric strength produce high energy density components exhibiting increased electrical energy storage. Mechanical (load bearing) improvements of the PMCs were attributed to covalently bonded nanometer and micrometer sized filler particles, as well as the continuous glass fiber, integrated into the resin systems which increased the structural characteristics of the cured composites. Breakdown voltage tests and dynamic mechanical analysis were employed to demonstrate that precise combinations of these constituents, under the proper processing conditions, can satisfy the needs presented by the aerospace industry and military forces.

The impact of ultra-low amounts of amino-modified MMT on dynamics and properties of densely cross-linked cyanate ester resins

NASA Astrophysics Data System (ADS)

Bershtein, Vladimir; Fainleib, Alexander; Egorova, Larisa; Gusakova, Kristina; Grigoryeva, Olga; Kirilenko, Demid; Konnikov, Semen; Ryzhov, Valery; Yakushev, Pavel; Lavrenyuk, Natalia

2015-04-01

Thermostable nanocomposites based on densely cross-linked cyanate ester resins (CER), derived from bisphenol E and doped by 0.01 to 5 wt. % amino-functionalized 2D montmorillonite (MMT) nanoparticles, were synthesized and characterized using Fourier transform infrared (FTIR), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), far-infrared (Far-IR), and creep rate spectroscopy (CRS) techniques. It was revealed that ultra-low additives, e.g., 0.025 to 0.1 wt. %, of amino-MMT nanolayers covalently embedded into CER network exerted an anomalously large impact on its dynamics and properties resulting, in particular, in some suppression of dynamics, increasing the onset of glass transition temperature by 30° to 40° and twofold rise of modulus in temperature range from 20°C to 200°C. Contrarily, the effects became negligibly small or even negative at increased amino-MMT contents, especially at 2 and 5 wt. %. That could be explained by TEM/EDXS data displaying predominance of individual amino-MMT nanolayers and their thin (2 to 3 nanolayers) stacks over more thick tactoids (5 to 10 nanolayers) and the large amino-MMT aggregates (100 to 500 nm in thickness) reversing the composite structure produced with increasing of amino-MMT content within CER matrix. The revealed effect of ultra-low amino-MMT content testifies in favor of the idea about the extraordinarily enhanced long-range action of the `constrained dynamics' effect in the case of densely cross-linked polymer networks.

Cyanate - An overlooked energy and nitrogen source in soils?

NASA Astrophysics Data System (ADS)

Mooshammer, Maria; Palatinszky, Márton; Herbold, Craig; Han, Ping; Daims, Holger; Richter, Andreas; Wagner, Michael

2016-04-01

Cyanate (NCO-) is a reduced nitrogen compound that is toxic to organisms due to its reactivity with nucleophilic groups in proteins. To lower cyanate concentrations within cells, a wide range of microorganisms possess a cyanase, which catalyzes the conversion of cyanate to ammonium and carbon dioxide. However, cyanate can also be useful for microbes by serving as a nitrogen source for cyanase-encoding microorganism, such as marine cyanobacteria (Kamennaya et al., 2008). Unexpectedly, we could recently demonstrate that at least one ammonia-oxidizing thaumarchaeote as well as nitrite-oxidizers thriving in consortia with ammonia-oxidizers can grow aerobically on cyanate as only energy and nitrogen source (Palatinszky et al., 2015). Furthermore, published metagenomes revealed that cyanase-encoding genes closely related to those of nitrifiers (ammonia- and nitrite-oxidizers) are widespread in the environment and encompass also cyanases affiliated with anammox organisms. Therefore, cyanate presumably presents an alternative nitrogen and also energy source for many microorganisms in aquatic and terrestrial environments. Surprisingly, cyanate concentrations and fluxes in natural environments are largely unknown, and environmental cyanate concentrations have only been studied in seawater so far, where it occurs in the nanomolar-range (Widner et al. 2013). No information about the importance of cyanate in soils is available, although urea that spontaneously decomposes to cyanate is the most used agricultural fertilizer on a global scale. Cyanate can have many fates in soils - it can be (1) used as nitrogen and/or energy source by cyanase-encoding microorganisms, (2) abiotically hydrolysed to ammonium and carbon dioxide, (3) adsorbed to soil particles, or (4) complexed with other compounds. Here we present the first measurements of cyanate concentrations in natural soils and results of experiments designed to differentiate between biotic and abiotic degradation of cyanate in soils. We also introduce new cultivation and labelling-techniques that should allow us to study the importance of cyanate for microbial metabolism in terrestrial ecosystems. References Kamennaya, N. A., M. Chernihovsky, and A. F. Post (2008). The cyanate utilization capacity of marine unicellular cyanobacteria. Limnol Oceanogr 53:2485-2494. Palatinszky, M., C. Herbold, N. Jehmlich, M. Pogoda, P. Han, M. von Bergen, I. Lagkouvardos, S. M. Karst, A. Galushko, H. Koch, D. Berry, H. Daims, and M. Wagner (2015). Cyanate as energy source for nitrifiers. Nature 524:105-108. Widner, B., M. R. Mulholland, and K. Mopper (2013). Chromatographic determination of nanomolar cyanate concentrations in estuarine and sea waters by precolumn fluorescence derivatization. Anal Chem 85:6661-6666.

Proteomics Analysis of the Effects of Cyanate on Chromobacterium violaceum Metabolism

PubMed Central

Baraúna, Rafael A.; Ciprandi, Alessandra; Santos, Agenor V.; Carepo, Marta S.P.; Gonçalves, Evonnildo C.; Schneider, Maria P.C.; Silva, Artur

2011-01-01

Chromobacterium violaceum is a gram-negative betaproteobacterium that has been isolated from various Brazilian ecosystems. Its genome contains the cyn operon, which gives it the ability to metabolize highly toxic cyanate into ammonium and carbon dioxide. We used a proteomics approach to investigate the effects of cyanate on the metabolism of this bacterium. The proteome of cells grown with and without cyanate was compared on 2-D gels. Differential spots were digested and identified by mass spectrometry. The bacterium was able to grow at concentrations of up to 1 mM cyanate. Eighteen spots were differentially expressed in the presence of cyanate, of which 16 were downregulated and only two were upregulated. An additional 12 spots were detected only in extracts of cells unexposed to cyanate, and one was expressed only by the exposed cells. Fourteen spots were identified, corresponding to 13 different proteins. We conclude that cyanate promotes expression of enzymes that combat oxidative stress and represses enzymes of the citric acid cycle, strongly affecting the energetic metabolism of the cell. Other proteins that were under-expressed in bacteria exposed to cyanate are involved in amino-acid metabolism or are hypothetical proteins, demonstrating that cyanate also affects expression of genes that are not part of the cyn operon. PMID:24710289

Alternative High Performance Polymers for Ablative Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Boghozian, Tane; Stackpoole, Mairead; Gonzales, Greg

2015-01-01

Ablative thermal protection systems are commonly used as protection from the intense heat during re-entry of a space vehicle and have been used successfully on many missions including Stardust and Mars Science Laboratory both of which used PICA - a phenolic based ablator. Historically, phenolic resin has served as the ablative polymer for many TPS systems. However, it has limitations in both processing and properties such as char yield, glass transition temperature and char stability. Therefore alternative high performance polymers are being considered including cyanate ester resin, polyimide, and polybenzoxazine. Thermal and mechanical properties of these resin systems were characterized and compared with phenolic resin.

The effect of reactor geometry on the synthesis of graphene materials in plasma jets

NASA Astrophysics Data System (ADS)

Shavelkina, M. B.; Amirov, R. H.; Shatalova, T. B.

2017-05-01

The possibility of synthesis of graphene and graphane (hydrogenated graphene) using the decomposition of hydrocarbons by thermal plasma has been investigated. Investigations of the influence of the plasma-forming gas on the efficiency of synthesis and the morphology of graphene materials were carried out. The synthesis products have been characterized by the methods of scanning microscopy, Raman spectroscopy and thermal analysis. It is found that the morphology of graphene materials is affected by the geometry of the reactor. It was demonstrated that the obtained graphene materials are uniformly distributed in the volume of plastic based on cyanate ester resins under mixing.

Epoxy-Based Organogels for Thermally Reversible Light Scattering Films and Form-Stable Phase Change Materials.

PubMed

Puig, Julieta; Dell' Erba, Ignacio E; Schroeder, Walter F; Hoppe, Cristina E; Williams, Roberto J J

2017-03-29

Alkyl chains of β-hydroxyesters synthesized by the capping of terminal epoxy groups of diglycidylether of bisphenol A (DGEBA) with palmitic (C16), stearic (C18), or behenic (C22) fatty acids self-assemble forming a crystalline phase. Above a particular concentration solutions of these esters in a variety of solvents led to supramolecular (physical) gels below the crystallization temperature of alkyl chains. A form-stable phase change material (FS-PCM) was obtained by blending the ester derived from behenic acid with eicosane. A blend containing 20 wt % ester was stable as a gel up to 53 °C and exhibited a heat storage capacity of 161 J/g, absorbed during the melting of eicosane at 37 °C. Thermally reversible light scattering (TRLS) films were obtained by visible-light photopolymerization of poly(ethylene glycol) dimethacrylate-ester blends (50 wt %) in the gel state at room temperature. The reaction was very fast and not inhibited by oxygen. TRLS films consisted of a cross-linked methacrylic network interpenetrated by the supramolecular network formed by the esters. Above the melting temperature of crystallites formed by alkyl chains, the film was transparent due to the matching between refractive indices of the methacrylic network and the amorphous ester. Below the crystallization temperature, the film was opaque because of light dispersion produced by the organic crystallites uniformly dispersed in the material. Of high significance for application was the fact that the contrast ratio did not depend on heating and cooling rates.

Epoxy hydantoins as matrix resins

NASA Technical Reports Server (NTRS)

Weiss, J.

1983-01-01

Tensile strength and fracture toughness of castings of the hydantoin resins cured with methylenedianiline are significantly higher than MY 720 control castings. Water absorption of an ethyl, amyl hydantoin formulation is 2.1 percent at equilibrium and Tg's are about 160 C, approximately 15 deg below the final cure temperature. Two series of urethane and ester-extended hydantoin epoxy resins were synthesized to determine the effect of crosslink density and functional groups on properties. Castings cured with methylenedianiline or with hexahydrophthalic anhydride were made from these compounds and evaluated. The glass transition temperatures, tensile strengths and moduli, and fracture toughness values were all much lower than that of the simple hydantoin epoxy resins. Using a methylene bishydantoin epoxy with a more rigid structure gave brittle, low-energy fractures, while a more flexible, ethoxy-extended hydantoin epoxy resin gave a very low Tg.

The urea decomposition product cyanate promotes endothelial dysfunction

PubMed Central

El-Gamal, Dalia; Rao, Shailaja Prabhakar; Holzer, Michael; Hallström, Seth; Haybaeck, Johannes; Gauster, Martin; Wadsack, Christian; Kozina, Andrijana; Frank, Saša; Schicho, Rudolf; Schuligoi, Rufina; Heinemann, Akos; Marsche, Gunther

2014-01-01

The dramatic cardiovascular mortality of chronic kidney disease patients is attributable in a significant proportion to endothelial dysfunction. Cyanate, a reactive species in equilibrium with urea, is formed in excess in chronic kidney disease. Cyanate is thought to have a causal role in promoting cardiovascular disease, but the underlying mechanisms remain unclear. Immunohistochemical analysis performed in the present study revealed that carbamylated epitopes associate mainly with endothelial cells in human atherosclerotic lesions. Cyanate treatment of human coronary artery endothelial cells reduced expression of endothelial nitric oxide synthase and increased tissue factor and plasminogen activator inhibitor-1 expression. In mice, administration of cyanate - promoting protein carbamylation at levels observed in uremic patients - attenuated arterial vasorelaxation of aortic rings in response to acetylcholine, without affecting sodium nitroprusside-induced relaxation. Total endothelial nitric oxide synthase and nitric oxide production were significantly reduced in aortic tissue of cyanate-treated mice. This coincided with a marked increase of tissue factor and plasminogen activator inhibitor-1 protein levels in aortas of cyanate-treated mice. These data provide evidence that cyanate compromises endothelial functionality in vitro and in vivo and may contribute to the dramatic cardiovascular risk of patients suffering from chronic kidney disease. PMID:24940796

A spectrophotometric determination of cyanate using reaction with 2-aminobenzoic acid.

PubMed

Guilloton, M; Karst, F

1985-09-01

A specific method has been devised for the assay of cyanate, based on the reaction with 2-aminobenzoic acid. Cyclization of the product in 6 N HCl results in the formation of 2,4(1H,3H)-quinazolinedione. Cyanate content of the samples can be measured by their absorbances at 310 nm. Alternatively, the second derivatives of the spectra can be recorded; the peak-to-peak height between the first maximum (330 nm) and the first minimum (317 nm) was shown to be proportional to the cyanate content. This method is suitable for the estimation of cyanate in aqueous solutions in the concentration range 0.01 to 2 mM. When added to blood plasma, cyanate could be detected down to 0.1 mM.

Di(cyanate Ester) Networks Based on Alternative Fluorinated Bisphenols with Extremely Low Water Uptake

DTIC Science & Technology

2013-11-01

radomes6  to magnet casings  for  thermonuclear  fusion  reactors7,8  and  support  structures   for  interplanetary  space  probes.9    These  properties...because  the  conversion  is  relatively  easy  to  quantify via methods such as FT‐IR spectroscopy,17 investiga‐ tions  of  structure ‐property...the  high‐temperature  resistance  and  mechanical  stiffness  associated with aromatic content, which  limits  their poten‐ tial  for high

A fluorescence-based method for cyanate analysis in ethanol/water media: correlation between cyanate presence and ethyl carbamate formation in sugar cane spirit.

PubMed

Ohe, Thiago Hideyuki Kobe; da Silva, Alexandre Ataide; Rocha, Thaís da Silva; de Godoy, Flávio Schutzer; Franco, Douglas Wagner

2014-10-01

Based on the fluorescence properties of 2,4-(1H,3H)-quinazolinedione, a product of the reaction between cyanate and 2-aminobenzoic acid, a simple, sensitive, selective, and reproducible method for the cyanate analysis in aqueous ethanolic media is proposed. In this method, λ(exc) and λ(em) are 310 and 410 nm, respectively, and the limits of detection and quantification are 2.2 × 10(-7) and 6.7 × 10(-7) mol/L, respectively. Under optimal conditions (pH = 4.5, 40% ethanol), a concentration of 5.0 × 10(-6) mol/L cyanate can be determined in a single measurement, at a 95% level of confidence, with an uncertainty of ± 0.13 × 10(-6) mol/L. Cyanide, thiocyanate, chloride, nitrate, and sulfate ions, as well as urea and urethane in concentrations 1 × 10(3) higher than that of cyanate do not interfere with the measurement. The methodology was applied to cyanate analyses in the different fractions of the sugarcane distillate and the data strongly suggest a correlation between the presence of urea in wine, and the cyanate and ethyl carbamate concentrations in the spirit. Based on the fluorescence properties of the reaction product between cyanate and 2-aminobenzoic acid, a method for assaying cyanate was devised. This procedure applied to the sugarcane distillate showed for the first time a correlation between cyanate presence and ethyl carbamate (EC) formation in the different fractions of the product. Therefore, the proposed methodology can be used to predict in freshly distillate sugar cane spirits the potential total concentration of EC to be formed. Therefore, these data could be used to advise about the necessity of implementing a procedure to reduce spirit EC concentration before the product reaches the market. © 2014 Institute of Food Technologists®

Synergistic Heterobimetallic Manifold for Expedient Manganese(I)-Catalyzed C-H Cyanation.

PubMed

Liu, Weiping; Richter, Sven C; Mei, Ruhuai; Feldt, Milica; Ackermann, Lutz

2016-12-12

The manganese-catalyzed cyanation of inert C-H bonds was achieved within a heterobimetallic catalysis regime. The manganese(I) catalysis proved widely applicable and enabled C-H cyanations on indoles, pyrroles and thiophenes by facile C-H manganesation. The robustness of the manganese catalyst set the stage for the racemization-free C-H cyanation of amino acids with excellent levels of positional and chemo selectivity by the new cyanating agent NCFS. Experimental and computational mechanistic studies provided strong support for a synergistic heterobimetallic activation mode, facilitating the key C-C formation. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Copper-Catalyzed Cyanation of Heterocycle Carbon-Hydrogen Bonds

PubMed Central

Hien-Quang, Do; Daugulis, Olafs

2010-01-01

A method for regioselective cyanation of heterocycles has been developed. A number of aromatic heterocycles as well as azulene can be cyanated in reasonable to good yields by using a copper cyanide catalyst and an iodine oxidant. PMID:20441204

Photo-assisted cyanation of transition metal nitrates coupled with room temperature C-C bond cleavage of acetonitrile.

PubMed

Zou, Shihui; Li, Renhong; Kobayashi, Hisayoshi; Liu, Juanjuan; Fan, Jie

2013-03-07

It is a challenge to use acetonitrile as a cyanating agent because of the difficulty in cleaving its C-CN bond. Herein, we report a mild photo-assisted route to conduct the cyanation of transition metal nitrates using acetonitrile as the cyanating agent coupled with room-temperature C-C bond cleavage. DFT calculations and experimental observations suggest a radical-involved reaction mechanism, which excludes toxicity from free cyanide ions.

Synthesis of the antileukemic compound N,N(11)-[5-[bis(2-chloroethyl)amino]-1, 3-phenylene]bisurea.

PubMed

Denny, G H; Ryder, M A; DeMarco, A M; Babson, R D

1976-03-01

Conversion of 5-nitro-1, 3-benzenedicarboxylic acid (1) to the diamide 2 followed by hypochlorite rearrangement to the idamine 3 and subsequent reaction with acetic anhydride gave the bisacetamide 4. Reduction to the amine 5 followed by treatment with ethylene oxide formed the diol 6. The latter was converted to the bistosylate 7, which undrewent facile displacement with lithium chloride in acetone to give the mustard 8. Removal of the acetyl groups with hydrochloric acid gave 9, which reacted with potassium cyanate to provide the bisurea 10. In an alternative, but less satisfactory synthesis of 10, the compound (5-nitro-1, 3-phenylene) biscarbamic acid diphenyl ester (11), or the corresponding diethyl ester 12, was converted by ammonolysis to 13. The nitrodiurea 13 was next reduced to the amine 14, the hydrochloride of which reacted with ethylene oxide to give the diol 15. Treatment of the latter in dimethylformamide with N-chlorosuccinimide in the presence of triphenylphosphine gave 10 in low yield. The nitrogen mustards 8, 9 and 10 showed significant antitumor activities against P388 lymphocytic leukemia in mice.

Next-generation avionics packaging and cooling 'test results from a prototype system'

NASA Astrophysics Data System (ADS)

Seals, J. D.

The author reports on the design, material characteristics, and test results obtained under the US Air Force's advanced aircraft avionics packaging technologies (AAAPT) program, whose charter is to investigate new designs and technologies for reliable packaging, interconnection, and thermal management. Under this program, AT&T Bell Laboratories has completed the preliminary testing of and is evaluating a number of promising materials and technologies, including conformal encapsulation, liquid flow-through cooling, and a cyanate ester backplane. A fifty-two module system incorporating these and and other technologies has undergone preliminary cooling efficiency, shock, sine and random vibration, and maintenance testing. One of the primary objectives was to evaluate the interaction compatibility of new materials and designs with other components in the system.

The millimeter wave spectrum of methyl cyanate: a laboratory study and astronomical search in space^.

PubMed

Kolesniková, L; Alonso, J L; Bermúdez, C; Alonso, E R; Tercero, B; Cernicharo, J; Guillemin, J-C

2016-07-01

The recent discovery of methyl isocyanate (CH 3 NCO) in Sgr B2(N) and Orion KL makes methyl cyanate (CH 3 OCN) a potential molecule in the interstellar medium. The aim of this work is to fulfill the first requirement for its unequivocal identification in space, i.e. the availability of transition frequencies with high accuracy. The room-temperature rotational spectrum of methyl cyanate was recorded in the millimeter wave domain from 130 to 350 GHz. All rotational transitions revealed A - E splitting owing to methyl internal rotation and were globally analyzed using the ERHAM program. The data set for the ground torsional state of methyl cyanate exceeds 700 transitions within J″ = 10 - 35 and [Formula: see text] and newly derived spectroscopic constants reproduce the spectrum close to the experimental uncertainty. Spectral features of methyl cyanate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methyl cyanate are provided.

Structural Peculiarities of Ion-Conductive Organic-Inorganic Polymer Composites Based on Aliphatic Epoxy Resin and Salt of Lithium Perchlorate.

PubMed

Matkovska, Liubov; Iurzhenko, Maksym; Mamunya, Yevgen; Tkachenko, Igor; Demchenko, Valeriy; Synyuk, Volodymyr; Shadrin, Andriy; Boiteux, Gisele

2017-12-01

The article is concerned with hybrid amorphous polymers synthesized basing on epoxy oligomer of diglycide aliphatic ester of polyethylene glycol that was cured by polyethylene polyamine and lithium perchlorate salt. Structural peculiarities of organic-inorganic polymer composites were studied by differential scanning calorimetry, wide-angle X-ray spectra, infrared spectroscopic, scanning electron microscopy, elemental analysis, and transmission and reflective optical microscopy. On the one hand, the results showed that the introduction of LiClO 4 salt into epoxy polymer leads to formation of the coordinative metal-polymer complexes of donor-acceptor type between central Li + ion and ligand. On the other hand, the appearance of amorphous microinclusions, probably of inorganic nature, was also found.

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

40 CFR 721.10367 - Hydroxy-aryl, polymer with substituted benzene, cyanate (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... benzene, cyanate (generic). 721.10367 Section 721.10367 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10367 Hydroxy-aryl, polymer with substituted benzene... substance identified generically as hydroxy-aryl, polymer with substituted benzene, cyanate (PMN P-10-83) is...

The millimeter wave spectrum of methyl cyanate: a laboratory study and astronomical search in space ⋆,⋆⋆

PubMed Central

Kolesniková, L.; Alonso, J. L.; Bermúdez, C.; Alonso, E. R.; Tercero, B.; Cernicharo, J.; Guillemin, J.-C.

2016-01-01

Aims The recent discovery of methyl isocyanate (CH3NCO) in Sgr B2(N) and Orion KL makes methyl cyanate (CH3OCN) a potential molecule in the interstellar medium. The aim of this work is to fulfill the first requirement for its unequivocal identification in space, i.e. the availability of transition frequencies with high accuracy. Methods The room-temperature rotational spectrum of methyl cyanate was recorded in the millimeter wave domain from 130 to 350 GHz. All rotational transitions revealed A-E splitting owing to methyl internal rotation and were globally analyzed using the ERHAM program. Results The data set for the ground torsional state of methyl cyanate exceeds 700 transitions within J″ = 10 – 35 and Ka″=0−13 and newly derived spectroscopic constants reproduce the spectrum close to the experimental uncertainty. Spectral features of methyl cyanate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methyl cyanate are provided. PMID:27721514

Simultaneous quantification of epoxy and hydroxy fatty acids as oxidation products of triacylglycerols in edible oils.

PubMed

Xia, Wei; Budge, Suzanne M

2018-02-16

Epoxy and hydroxy fatty acids are important intermediates during lipid oxidation; quantification of both structures may help evaluate the extent of competition among various lipid oxidation pathways. This article describes a method to simultaneously determine saturated- and unsaturated- epoxy and hydroxy fatty acids derived from oxidation of vegetable oils. The experimental procedures employed transesterification with sodium methoxide, separation of epoxy and hydroxy fatty acid methyl esters (FAME) using solid-phase extraction (SPE), and trimethylsilyl (TMS) derivatization of hydroxy groups. GC-MS was used to identify the epoxy and hydroxy FAME in two different SPE fractions, while GC-flame ionization detection (GC-FID) was used to determine their quantities. Epoxy-octadecanoate/octadecenoate and hydroxy-octadecanoate/octadecenoate/octadecadienoate were determined as lipid oxidation products generated from oxidation of sunflower and canola oils. An isomer of methyl 13-hydroxyoctadeca-9,11-dienoate (13-HODE) TMS ether co-eluted with methyl 15-hydroxyoctadeca-9,12-dienoate TMS ether, which was only present in canola oil; thus, GC-MS-selected ion monitoring (GC-MS-SIM) was used to determine the concentration of 13-HODE. The proposed method has been successfully applied to monitor epoxy and hydroxy fatty acids in sunflower oil and canola oil oxidized at 40 °C. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of reaction condition on viscosity of polyurethane modified epoxy based on glycerol monooleate

NASA Astrophysics Data System (ADS)

Triwulandari, Evi; Ramadhan, Mohammad Kemilau; Ghozali, Muhammad

2017-01-01

Polyurethane modified epoxy based on glycerol monooleate (PME-GMO) was synthesized. GMO as polyol for synthesis of PME-GMO was synthesized via Fisher Esterification between oleic acid from palm oil and glycerol by using sulfuric acid as catalyst with time variation i.e. 3, 4, 5 and 6 hours at 160°C. Characterizations of GMO were carried out by analysis of acid number, hydroxyl value and FTIR. The data show that the conversion of oleic acid to ester compound is directly proportional with the increasing of reaction time but the enhancement is not significant after 3 hours. Furthermore, GMO product was used as polyol for modification of epoxy with polyurethane. Modification of epoxy with polyurethane was performed by reacted epoxy, tolonate and GMO simultaneously in one step. In this research, the reaction condition was varied i.e. time reaction (0.5; 1; 1.5; 2; 2.5 hours), composition of polyurethane used (10%, 20% toward epoxy) and rasio of tolonate and GMO (NCO/OH ratio) as component of polyurethane (1.5 and 2.5). Characterization of polyurethane modified epoxy based on glycerol (PME-GMO) was conducted by viscosity and FTIR analysis. The viscosity of PME-GMO increased with increasing of reaction time, polyurethane composition and NCO/OH ratio.

Novel matrix resins for composites for aircraft primary structures, phase 1

NASA Technical Reports Server (NTRS)

Woo, Edmund P.; Puckett, P. M.; Maynard, S.; Bishop, M. T.; Bruza, K. J.; Godschalx, J. P.; Mullins, M. J.

1992-01-01

The objective of the contract is the development of matrix resins with improved processability and properties for composites for primarily aircraft structures. To this end, several resins/systems were identified for subsonic and supersonic applications. For subsonic aircraft, a series of epoxy resins suitable for RTM and powder prepreg was shown to give composites with about 40 ksi compressive strength after impact (CAI) and 200 F/wet mechanical performance. For supersonic applications, a thermoplastic toughened cyanate prepreg system has demonstrated excellent resistance to heat aging at 360 F for 4000 hours, 40 ksi CAI and useful mechanical properties at greater than or equal to 310 F. An AB-BCB-maleimide resin was identified as a leading candidate for the HSCT. Composite panels fabricated by RTM show CAI of approximately 50 ksi, 350 F/wet performance and excellent retention of mechanical properties after aging at 400 F for 4000 hours.

Antioxidation behavior of milkweed oil 4-hydroxy-3-methyoxycinnamate esters in phospholipid bilayers

USDA-ARS?s Scientific Manuscript database

Milkweed (Asclepia syriaca) has seed oil that is rich in polyunsaturated triacylglycerides that contain olefinic groups. The olefinic groups can be chemically oxidized to form either epoxy or polyhydroxy triacylglycerides that can be esterified with trans-4-hydroxy-3-methoxoycinnamic acid, commonly...

Cutin composition of five finnish berries.

PubMed

Kallio, Heikki; Nieminen, Riikka; Tuomasjukka, Saska; Hakala, Mari

2006-01-25

The raw cutin (i.e., extractive-free isolated cuticular membrane) fraction from Finnish berries, sea buckthorn (Hippophaë rhamnoides), black currant (Ribes nigrum), cranberry (Vaccinium oxycoccos), lingonberry (Vaccinium vitis-idaea), and bilberry (Vaccinium myrtillus), was depolymerized by NaOMe-catalyzed methanolysis. The composition of cutin monomers was determined by GC-(EI)MS analysis either as methyl esters or as TMSi esters, with OH groups derivatized to TMSi ethers. There was a notable difference in the degree of depolymerization, ranging from 6 to 47%. The extractive-free berry cuticle, that is, raw cutin, thus contains <50% polyester polymer cutin. The predominant cutin monomers were C(16) and C(18) omega-hydroxy acids with midchain functionalities, mainly epoxy and hydroxyl groups. Typically, the major compounds were 9,10-epoxy-18-hydroxyoctadecanoic acid, 10,16-dihydroxyhexadecanoic acid, 9,10,18-trihydroxyoctadecanoic acid, 9,10-epoxy-18-hydroxyoctadec-12-enoic acid, and 18-hydroxyoctadec-9-enoic acid. The amount of epoxyacids was rather high in sea buckthorn ( approximately 70%) and cranberry ( approximately 60%), compared with the other berries. The black currant cutin differed from that of the other berries with a significant portion of hydroxyoxohexadecanoic acid ( approximately 12% of total monomers). This investigation of the cuticular hydroxy acids of five Finnish berries is part of the exploitation of the northern natural resources related to the chemical composition, nutritional value, and sensory properties.

A cyanase is transcriptionally regulated by arginine and involved in cyanate decomposition in Sordaria macrospora.

PubMed

Elleuche, Skander; Pöggeler, Stefanie

2008-11-01

Cyanase degrades toxic cyanate to NH3 and CO2 in a bicarbonate-dependent reaction. High concentrations of cyanate are fairly toxic to organisms. Here, we characterize a eukaryotic cyanase for the first time. We have isolated the cyn1 gene encoding a cyanase from the filamentous ascomycete Sordaria macrospora and functionally characterized the cyn1 product after heterologous expression in Escherichia coli. Site-directed mutagenesis confirmed a predicted catalytic centre of three conserved amino-acids. A Deltacyn1 knockout in S. macrospora was totally devoid of cyanase activity and showed an increased sensitivity to exogenously supplied cyanate in an arginine-depleted medium, defects in ascospore germination, but no other obvious morphological phenotype. By means of real-time PCR we have demonstrated that the transcriptional level of cyn1 is markedly elevated in the presence of cyanate and down-regulated by addition of arginine. The putative functions of cyanase in fungi are discussed.

A new esterase for the cleavage of pivalic acid-containing prodrug esters of cephalosporins.

PubMed

Sauber, K; Aretz, W; Meiwes, J; Wollmann, T

1996-07-01

An extracellular esterase from the actinomycetes Amycolatopsis orientalis was found by screening. It is capable of splitting the isomeric mixture (K/J) of (I, Scheme 1) into 7-amino-3-methoxymethyl-3-cephem-4-carboxylic acid, pivalic acid, and acetaldehyde with a high yield. The purified enzyme of 55.4 Kd by SDS-PAGE shows an N-terminal sequence of VRTCADLVRTYDLPGAVTH. The isoelectric point is 8.9 +/- 0.1. It can be immobilized with good yield to VA-Epoxy Biosynth. Besides the above-mentioned reaction, the esterase cleaves many other esters such as methyl-2-chloropropionic acid.

Effect of Liquid-Crystalline Epoxy Backbone Structure on Thermal Conductivity of Epoxy-Alumina Composites

NASA Astrophysics Data System (ADS)

Giang, Thanhkieu; Kim, Jinhwan

2017-01-01

In a series of papers published recently, we clearly demonstrated that the most important factor governing the thermal conductivity of epoxy-Al2O3 composites is the backbone structure of the epoxy. In this study, three more epoxies based on diglycidyl ester-terminated liquid-crystalline epoxy (LCE) have been synthesized to draw conclusions regarding the effect of the epoxy backbone structure on the thermal conductivity of epoxy-alumina composites. The synthesized structures were characterized by proton nuclear magnetic resonance (1H-NMR) and Fourier-transform infrared (FT-IR) spectroscopy. Differential scanning calorimetry, thermogravimetric analysis, and optical microscopy were also employed to examine the thermal and optical properties of the synthesized LCEs and the cured composites. All three LCE resins exhibited typical liquid-crystalline behaviors: clear solid crystalline state below the melting temperature ( T m), sharp crystalline melting at T m, and transition to nematic phase above T m with consequent isotropic phase above the isotropic temperature ( T i). The LCE resins displayed distinct nematic liquid-crystalline phase over a wide temperature range and retained liquid-crystalline phase after curing, with high thermal conductivity of the resulting composite. The thermal conductivity values ranged from 3.09 W/m-K to 3.89 W/m-K for LCE-Al2O3 composites with 50 vol.% filler loading. The steric effect played a governing role in the difference. The neat epoxy resin thermal conductivity was obtained as 0.35 W/m-K to 0.49 W/m-K based on analysis using the Agari-Uno model. The results clearly support the objective of this study in that the thermal conductivity of the LCE-containing networks strongly depended on the epoxy backbone structure and the degree of ordering in the cured network.

3D Multifunctional Ablative Thermal Protection System

NASA Technical Reports Server (NTRS)

Feldman, Jay; Venkatapathy, Ethiraj; Wilkinson, Curt; Mercer, Ken

2015-01-01

NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule is a 3-dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad serves first as a structural component and later as an ablative heat shield, partially consumed on Earth re-entry. This presentation will summarize the development of a new 3D quartz cyanate ester composite material, 3-Dimensional Multifunctional Ablative Thermal Protection System (3D-MAT), designed to meet the mission requirements for the Orion compression pad. Manufacturing development, aerothermal (arc-jet) testing, structural performance, and the overall status of material development for the 2018 EM-1 flight test will be discussed.

Verification Test for Ultra-Light Deployment Mechanism for Sectioned Deployable Antenna Reflectors

NASA Astrophysics Data System (ADS)

Zajac, Kai; Schmidt, Tilo; Schiller, Marko; Seifart, Klaus; Schmalbach, Matthias; Scolamiero, Lucio

2013-09-01

The ultra-light deployment mechanism (UDM) is based on three carbon fibre reinforced plastics (CFRP) curved tape springs made of carbon fibre / cyanate ester prepregs.In the frame of the activity its space application suitability for the deployment of solid reflector antenna sections was investigated. A projected diameter of the full reflector of 4 m to 7 m and specific mass in the order of magnitude of 2.6kg/m2 was focused for requirement derivation.Extensive verification tests including health checks, environmental and functional tests were carried out with an engineering model to enable representative characterizing of the UDM unit.This paper presents the design and a technical description of the UDM as well as a summary of achieved development status with respect to test results and possible design improvements.

Damping properties of fiber reinforced composite suitable for stayed cable

NASA Astrophysics Data System (ADS)

Li, Jianzhi; Sun, Baochen; Du, Yanliang

2011-11-01

Carbon fiber reinforced plastics (CFRP) cables were initially most investigated to replace steel cables. To further explore the advantages of FRP cables, the potential ability of vibration control is studied in this paper emphasizing the designable characteristic of hybrid FRP cables. Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

Damping properties of fiber reinforced composite suitable for stayed cable

NASA Astrophysics Data System (ADS)

Li, Jianzhi; Sun, Baochen; Du, Yanliang

2012-04-01

Carbon fiber reinforced plastics (CFRP) cables were initially most investigated to replace steel cables. To further explore the advantages of FRP cables, the potential ability of vibration control is studied in this paper emphasizing the designable characteristic of hybrid FRP cables. Fiber reinforced vinyl ester composites and fiber reinforced epoxy composites were prepared by the pultrusion method. Due to the extensive application of fiber reinforced composites, the temperature spectrum and frequency spectrum of loss factor for the composite were tested using dynamic mechanical analysis (DMA) equipment. The damping properties and damping mechanism of the composite were investigated and discussed at different temperatures and frequencies. The result indicates that the loss factor of the composites is increasing with the increase of the frequency from 0.1Hz to 2 Hz and decreasing with the decrease of the temperature from -20°C to 60°C. The loss factor of the carbon fiber composite is higher than that of the glass fiber for the same matrix. The loss factor of the vinyl ester composite is higher than that of the epoxy composite for the same fiber.

Characterization of aerosols and fibers emitted from composite materials combustion.

PubMed

Chivas-Joly, C; Gaie-Levrel, F; Motzkus, C; Ducourtieux, S; Delvallée, A; De Lagos, F; Nevé, S Le; Gutierrez, J; Lopez-Cuesta, J-M

2016-01-15

This work investigates the aerosols emitted during combustion of aircraft and naval structural composite materials (epoxy resin/carbon fibers and vinyl ester/glass fibers and carbon nanotubes). Combustion tests were performed at lab-scale using a modified cone calorimeter. The aerosols emitted have been characterized using various metrological devices devoted to the analysis of aerosols. The influence of the nature of polymer matrices, the incorporation of fibers and carbon nanotubes as well as glass reinforcements on the number concentration and the size distribution of airborne particles produced, was studied in the 5 nm-10 μm range. Incorporation of carbon fibers into epoxy resin significantly reduced the total particle number concentration. In addition, the interlaced orientation of carbon fibers limited the particles production compared to the composites with unidirectional one. The carbon nanotubes loading in vinyl ester resin composites influenced the total particles production during the flaming combustion with changes during kinetics emission. Predominant populations of airborne particles generated during combustion of all tested composites were characterized by a PN50 following by PN(100-500). Copyright © 2015 Elsevier B.V. All rights reserved.

Two cases of occupational allergic contact dermatitis from a cycloaliphatic epoxy resin in a neat oil: Case Report

PubMed Central

Jensen, Charlotte D; Andersen, Klaus E

2003-01-01

Background Metal-working fluids contain complex mixtures of chemicals and metal workers constitute a potential risk group for the development of allergic contact dermatitis. Case presentation Two metal workers developed allergic contact dermatitis on the hands and lower arms from exposure to a neat oil used in metal processing. Patch testing revealed that the relevant contact allergen was a cycloaliphatic epoxy resin, 1,2-cyclohexanedicarboxylic acid, bis(oxiranylmethyl) ester, added to the oil as a stabilizer. None of the patients had positive reactions to the bisphenol A-based epoxy resin in the standard series. Conclusions These cases emphasize that well-known contact allergens may show up from unexpected sources of exposure. Further, it can be a long-lasting, laborious process to detect an occupational contact allergen and cooperation from the patient and the manufacturer of the sensitizing product is essential. PMID:12685935

Lipase catalyzed epoxidation of fatty acid methyl esters derived from unsaturated vegetable oils in absence of carboxylic acid.

PubMed

Sustaita-Rodríguez, Alejandro; Ramos-Sánchez, Víctor H; Camacho-Dávila, Alejandro A; Zaragoza-Galán, Gerardo; Espinoza-Hicks, José C; Chávez-Flores, David

2018-04-11

Nowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives. In this research article, grapeseed, avocado and olive oils naturally containing high percents of mono and poly unsaturations were used as starting materials for the production of unsaturated fatty acid methyl esters. The effect of lauric acid as an active oxygen carrier was studied on epoxidation reactions where unsaturated fatty acid methyl esters were converted to epoxy fatty acid methyl esters using immobilized Candida antarctica Lipase type B as catalyst and hydrogen peroxide as oxygen donor at mild temperature and pressure conditions. After this study it was confirmed by 1 H NMR, 13 C NMR and GC-MS that the addition of lauric acid to the enzymatic reaction is unnecessary to transform the alkenes in to epoxides. It was found that quantitative conversions were possible in despite of a carboxylic acid absence.

Synthetic approach to the AB ring system of ouabain.

PubMed

Jung, Michael E; Piizzi, Grazia

2003-04-04

Several novel hydroxylated cis-decalin derivatives, potential intermediates for the synthesis of the AB ring system of the important cardiotonic steroid ouabain, have been synthesized from commercially available starting materials. The first step in the preparation of these highly functionalized intermediates is a Robinson annulation of the beta-keto ester 6 and the 4-silyl-3-buten-2-one 5 to furnish the octalone 4 with good diastereoselectivity in fair yield (due to competition with a novel silicon-to-carbon phenyl migration). Reduction of the epoxy alcohol 3 (derived from 4 in two high-yielding steps) with LiAlH(4) gave a mixture of the desired triol 11 along with the product of an unusual reductive opening at the tertiary carbon, namely the triol 12. A plausible mechanism for this unusual reduction is presented as are possible methods for avoiding it. In particular, reduction of the corrresponding epoxy ketone 15 with aluminum amalgam proceeded in good yield to give the hydroxy ketone 16. Also reduction of the epoxide ester having the inverted stereochemistry at C3 afforded the desired tertiary alcohol 33 in good yield. Another approach using the beta,gamma-unsaturated ketal 38 permitted the formation of the tertiary alcohol 40. Fleming oxidation of the related, very functionalized silane 39 afforded the desired 1beta-alcohol 41 in fair yield. Finally a novel rearrangement was observed when the epoxy alcohol 24 was treated with DIBAL to effect loss of the angular hydroxymethyl group to produce the tetrasubstitued alkene 29 in high yield.

17-hydroxy oleic acid as precursor for unsaturated and epoxy fatty acid estolides: application as plasticizers in poly(3-hydroxybutyrate) films

USDA-ARS?s Scientific Manuscript database

Estolides (oligomeric fatty acid esters) have been known for close to a century but only within the last few years have they been efficiently produced with control over molecular structure. While estolides are commonly associated with lubricant applications, they can also be beneficial as plasticizi...

Improvements to hydroxymethylated resorcinol coupling agent for durable bonding to wood

Treesearch

Alfred W. Christiansen; E. Arnold Okkonen

2003-01-01

Improving the exterior quality bonding of wood to epoxy adhesive resins is important for bonding glass-fiber-reinforced vinyl ester resin laminae to glulam structural members, as well as for repairing glulam members in exterior applications on site. The coupling agent for these applications, hydroxymethylated resorcinol (HMR), was recently improved by using a novolak...

High-Performance Synthetic Fibers for Composites

DTIC Science & Technology

1992-04-01

under evaluation today include polyether ether ketone , polyamide, 23 polyamideimide, polyimide, polysulfone, and polyphenylene sulfide. Epoxy resins...shrinkage under intense neutron radiation . This attribute, together with other properties of high-temperature strength, toughness, and low nuclear...and (2) liquid or solid resins cross-linked with other esters in chopped-fiber and mineral-filled molding compounds. Polyether ether ketone (PEEK) A

KSC-08pd2650

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians clean contamination from the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2651

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician cleans contamination from the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2648

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician cleans contamination from the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2649

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician cleans contamination from the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2647

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Super Lightweight Interchangeable Carrier, or SLIC, is uncovered so that technicians can clean contaminants found earlier. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

A novel pink-pigmented facultative methylotroph, Methylobacterium thiocyanatum sp. nov., capable of growth on thiocyanate or cyanate as sole nitrogen sources.

PubMed

Wood, A P; Kelly, D P; McDonald, I R; Jordan, S L; Morgan, T D; Khan, S; Murrell, J C; Borodina, E

1998-02-01

The isolation and properties of a novel species of pink-pigmented methylotroph, Methylobacterium thiocyanatum, are described. This organism satisfied all the morphological, biochemical, and growth-substrate criteria to be placed in the genus Methylobacterium. Sequencing of the gene encoding its 16S rRNA confirmed its position in this genus, with its closest phylogenetic relatives being M. rhodesianum, M. zatmanii and M. extorquens, from which it differed in its ability to grow on several diagnostic substrates. Methanol-grown organisms contained high activities of hydroxypyruvate reductase -3 micromol NADH oxidized min-1 (mg crude extract protein)-1], showing that the serine pathway was used for methylotrophic growth. M. thiocyanatum was able to use thiocyanate or cyanate as the sole source of nitrogen for growth, and thiocyanate as the sole source of sulfur in the absence of other sulfur compounds. It tolerated high concentrations (at least 50 mM) of thiocyanate or cyanate when these were supplied as nitrogen sources. Growing cultures degraded thiocyanate to produce thiosulfate as a major sulfur end product, apparently with the intermediate formation of volatile sulfur compounds (probably hydrogen sulfide and carbonyl sulfide). Enzymatic hydrolysis of thiocyanate by cell-free extracts was not demonstrated. Cyanate was metabolized by means of a cyanase enzyme that was expressed at approximately sevenfold greater activity during growth on thiocyanate [Vmax 634 +/- 24 nmol NH3 formed min-1 (mg protein)-1] than on cyanate [89 +/- 9 nmol NH3 min-1 (mg protein)-1]. Kinetic study of the cyanase in cell-free extracts showed the enzyme (1) to exhibit high affinity for cyanate (Km 0.07 mM), (2) to require bicarbonate for activity, (3) to be subject to substrate inhibition by cyanate and competitive inhibition by thiocyanate (Ki 0.65 mM), (4) to be unaffected by 1 mM ammonium chloride, (5) to be strongly inhibited by selenocyanate, and (6) to be slightly inhibited by 5 mM thiosulfate, but unaffected by 0.25 mM sulfide or 1 mM thiosulfate. Polypeptides that might be a cyanase subunit (mol.wt. 17.9 kDa), a cyanate (and/or thiocyanate) permease (mol.wt. 25.1 and 27.2 kDa), and a putative thiocyanate hydrolase (mol.wt. 39.3 kDa) were identified by SDS-PAGE. Correlation of the growth rate of cultures with thiocyanate concentration (both stimulatory and inhibitory) and the kinetics of cyanase activity might indicate that growth on thiocyanate involved the intermediate formation of cyanate, hence requiring cyanase activity. The very high activity of cyanase observed during growth on thiocyanate could be in compensation for the inhibitory effect of thiocyanate on cyanase. Alternatively, thiocyanate may be a nonsubstrate inducer of cyanase, while thiocyanate degradation itself proceeds by a carbonyl sulfide pathway not involving cyanate. A formal description of the new species (DSM 11490) is given.

Durability of polymer matrix composites for infrastructure: The role of the interphase

NASA Astrophysics Data System (ADS)

Verghese, Kandathil Nikhil Eapen

1999-12-01

As fiber reinforced polymer matrix composites find greater use in markets such as civil infrastructure and ground transportation, the expectations placed on these materials are ever increasing. The overall cost and reliability have become the drivers of these high performance materials and have led to the disappearance of resins such as bismaleimides (BMI). cyanate esters and other high performance polyimides and epoxys. In their place polymers, such polyester and vinylester have arisen. The reinforcing fiber scenario has also undergone changes from the high quality and performance assured IM7 and AS4 to cheaper and hybrid systems consisting of both glass and low cost carbon. Manufacturing processes have had their share of changes too with processes such as pultrusion and other mass production techniques replacing hand lay-up and resin transfer molding. All of this has however come with little or no concession on material performance. The motivation of the present research has therefore been to try to improve the properties of these low cost composites by better understanding the constituent materials (fiber and matrix) and the region that lies in-between them namely the interphase. In order to achieve this. working with controls is necessary and the present discourse therefore deals with the AS4 fiber system from Hexcel Corporation and the vinyl ester resin, Derakane 441-400 from The Dow Chemical Company. The following eight chapters sum up the work done thus far on composites made with sized fibers and the above mentioned resin and fiber systems. They are in the form of publications that have either been accepted. submitted or going to be submitted to various peer reviewed journals. The sizings used have been poly(vinylpyrrolidone) PVP and Polyhydroxyether (Phenoxy) thermoplastic polymers and G' an industrial sizing material supplied by Hexcel. A number of issues have been addressed ranging from viscoelastic relaxation to enviro-mechanical durability. Chapter 1 deals with the influence of the sizing material on the fatigue response of cross ply composites made with the help of resin infusion molding. Chapter 2 describes the effects of a controlled set of interphase polymers that have the saine chemical structure but differ from each other in polarity. The importance of the atomic force microscope (AFM) to view and perform nano-indentations on the interphase regions has been demonstrated. Finally, it attempts to tie everything together with the help of the fatigue response of the different composites. Chapter 3 deals only with the vinyl ester resin and examines the influence of network structure on the molecular relaxation behavior (cooperativity) of the glassy polymer. It also tries to make connections between structural features of the glass and fracture toughness as measured in it's glassy state. Chapter 4 extends the results obtained in chapter 3 to examine the cooperativity of pultruded composites made with the different sizings. A correlation between strength and cooperativity is found to exist, with systems having greater cooperativity being stronger. Chapter 5 moves into the area of hygrothermal aging of Derakane 441-400 resin. It looks specifically at identifying a mechanism for the unusual moisture uptake behavior of the polymer subjected to a thermal-spiking environment. This it does by identifying the presence of hydrogen bonding in the resin. Finally, chapters 6 to 8 present experimental and analytical results obtained on PVP K90, Phenoxy and G' sized, AS4/Derakane 411-350 LI vinyl ester composites that were pultruded at Strongwell Inc., on their lab-scale pultruder in Bristol, Virginia.

Effects of Cyanate and 2,3-Diphosphoglycerate on Sickling RELATIONSHIP TO OXYGENATION

PubMed Central

Jensen, Michael; Bunn, H. Franklin; Halikas, George; Kan, Yuet Wai; Nathan, David G.

1973-01-01

Cyanate and 2,3-diphosphoglycerate (2,3-DPG) both influence the oxygen affinity of hemoglobin. The studies presented here concern the effects of these compounds on the sickling phenomenon. The inhibitory effect of cyanate on sickling is largely due to the fact that it increases the percentage of oxyhemoglobin S at a given oxygen tension. In addition, cyanate inhibits sickling by a mechanism that is independent of oxygenation. In this paper, we have demonstrated that the viscosity of carbamylated sickle blood was lower than that of non-carbamylated controls at the same oxygen saturation. Furthermore, carbamylation resulted in an increase in the minimum concentration of deoxy-sickle hemoglobin required for gelation. Like cyanate, 2,3-DPG affected sickling of intact erythrocytes by two mechanisms. Since 2,3-DPG decreases the percentage of oxyhemoglobin S at a given oxygen tension, sickling is enhanced. In addition, 2,3-DPG had a direct effect. When the intracellular 2,3-DPG concentration was increased in vitro, a greater percentage of cells were sickled at a given oxygen saturation. Conversely, sickling was inhibited in cells in which 2,3-DPG was artificially lowered. These data indicate that the enhancement of sickling by 2,3-DPG is in part independent of its influence on oxygen affinity. PMID:4729047

The synthesis and dynamics research of new curing agent for epoxy resin

NASA Astrophysics Data System (ADS)

Peng, Yongli; Huang, Hengyu; Sun, Yong

2017-05-01

Two-step synthesis of trimellitic anhydride trimellitic anhydride n - butyl ester (TMNB) was introduced which could be used as an epoxy resin curing agent. The kinetics of the curing reaction was analyzed by N-order model and autocatalytic model. The curing kinetics parameters, the results show that the curing activation energy (Ea) of this system was 35.79kJ / mol. The kinetic equation of curing was d/a d t =2.1061 ×104e x p (-35.79/R T ) α0.5163(l-α ) 0.366 . Combined with β-1 / T extrapolation and experimental adjustment to obtain the resin system curing process: 75°C for 1h, 140°C for 3h, 160°C for 2h.

Room temperature decarboxylative cyanation of carboxylic acids using photoredox catalysis and cyanobenziodoxolones: a divergent mechanism compared to alkynylation† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc04907a Click here for additional data file.

PubMed Central

Le Vaillant, Franck; Wodrich, Matthew D.

2017-01-01

The one-step conversion of aliphatic carboxylic acids to the corresponding nitriles has been accomplished via the merger of visible light mediated photoredox and cyanobenziodoxolones (CBX) reagents. The reaction proceeded in high yields with natural and non-natural α-amino and α-oxy acids, affording a broad scope of nitriles with excellent tolerance of the substituents in the α position. The direct cyanation of dipeptides and drug precursors was also achieved. The mechanism of the decarboxylative cyanation was investigated both computationally and experimentally and compared with the previously developed alkynylation reaction. Alkynylation was found to favor direct radical addition, whereas further oxidation by CBX to a carbocation and cyanide addition appeared more favorable for cyanation. A concerted mechanism is proposed for the reaction of radicals with EBX reagents, in contrast to the usually assumed addition elimination process. PMID:28451301

The structure and mechanism of stem bromelain. Evaluation of the homogeneity of purified stem bromelain, determination of the molecular weight and kinetic analysis of the bromelain-catalysed hydrolysis of N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester

PubMed Central

Wharton, Christopher W.

1974-01-01

1. Purified stem bromelain (EC 3.4.22.4) was eluted from Sephadex G-100 as a single peak. The specific activity across the elution peak was approximately constant towards p-nitrophenyl hippurate but increased with elution volume with N2-benzoyl-l-arginine ethyl ester as substrate. 2. The apparent molecular weight, determined by elution analysis on Sephadex G-100, is 22500±1500, an anomalously low value. 3. Purified stem bromelain was eluted from CM-cellulose CM-32 as a single peak and behaved as a single species during column electrophoresis on Sephadex G-100. 4. Purified stem bromelain migrates as a single band during polyacrylamide-gel electrophoresis under a wide variety of conditions. 5. The molecular weight determined by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate is 28500±1000. 6. Sedimentation-velocity and equilibrium-ultracentrifugation experiments, under a variety of conditions, indicate that bromelain is an apparently homogeneous single peptide chain of mol.wt. 28400±1400. 7. The N-terminal amino acid composition is 0.64±0.04mol of valine and 0.36±0.04mol of alanine per mol of enzyme of mol.wt. 28500. (The amino acid recovery of the cyanate N-terminal amino acid analysis was standardized by inclusion of carbamoyl-norleucine at the cyclization stage.) 8. The pH-dependence of the Michaelis parameters of the bromelain-catalysed hydrolysis of N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester was determined. 9. The magnitude and pH-dependence of the Michaelis parameters have been interpreted in terms of the mechanism of the enzyme. 10. The enzyme is able to bind N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester relatively strongly but seems unable to make use of the binding energy to promote catalysis. PMID:4462742

Pd-Metalated Conjugated Nanoporous Polycarbazoles for Additive-Free Cyanation of Aryl Halides: Boosting Catalytic Efficiency through Spatial Modulation

DOE PAGES

Ding, Shunmin; Tian, Chengcheng; Zhu, Xiang; ...

2017-03-23

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed in this paper to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. Finally, the catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

New biobased high functionality polyols and their use in polyurethane coatings.

PubMed

Pan, Xiao; Webster, Dean C

2012-02-13

High-functionality polyols for application in polyurethanes (PUs) were prepared by epoxide ring-opening reactions from epoxidized sucrose esters of soybean oil-epoxidized sucrose soyates-in which secondary hydroxyl groups were generated from epoxides on fatty acid chains. Ester polyols were prepared by using a base-catalyzed acid-epoxy reaction with carboxylic acids (e.g., acetic acid); ether polyols were prepared by using an acid-catalyzed alcohol-epoxy reaction with monoalcohols (e.g., methanol). The polyols were characterized by using gel permeation chromatography, FTIR spectroscopy, (1)H NMR spectroscopy, differential scanning calorimetry (DSC), and viscosity measurements. PU thermosets were prepared by using aliphatic polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate. The properties of the PUs were studied by performing tensile testing, dynamic mechanical analysis, DSC, and thermogravimetric analysis. The properties of PU coatings on steel substrates were evaluated by using ASTM methods to determine coating hardness, adhesion, solvent resistance, and ductility. Compared to a soy triglyceride polyol, sucrose soyate polyols provide greater hardness and range of cross-link density to PU thermosets because of the unique structure of these macromolecules: well-defined compact structures with a rigid sucrose core coupled with high hydroxyl group functionality. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Studies on Automated Manufacturing of High Performance Composites

NASA Technical Reports Server (NTRS)

Cano, R. J.; Belvin, H. L.; Hulcher, A. B.; Grenoble, R. W.

2001-01-01

The NASA Langley Research Center fiber placement facility has proven to be a valuable asset for obtaining data, experience, and insights into the automated fabrication of high performance composites. The facility consists of two automated devices: an Asea Brown Boveri (ABB) robotic arm with a modified heated head capable of hot gas and focused infrared heating and a 7' x 17' gantry containing a feeder head, rotating platform, focused infrared lamp and e-beam gun. While uncured thermoset tow and tape, e.g., epoxy and cyanate prepreg, can be placed with a robot, the placement facility s most powerful attribute is the ability to place thermoplastic and e-beam curable material to net shape. In recent years, ribbonizing techniques have been developed to make high quality thermoplastic and thermoset dry material forms to the standards required for robotic placement. A variety of composites have been fabricated from these ribbons by heated head tow and tape placement including both flat plates and cylinders. Composite mechanical property values of the former were between 85 and 100 percent of those obtained by hand lay-up/autoclave processing.

Azobisisobutyronitrile initiated aerobic oxidative transformation of amines: coupling of primary amines and cyanation of tertiary amines.

PubMed

Liu, Lianghui; Wang, Zikuan; Fu, Xuefeng; Yan, Chun-Hua

2012-11-16

In the presence of a catalytic amount of radical initiator AIBN, primary amines are oxidatively coupled to imines and tertiary amines are cyanated to α-aminonitriles. These "metal-free" aerobic oxidative coupling reactions may find applications in a wide range of "green" oxidation chemistry.

Copper(II) catalysis in cyanide conversion into ethyl carbamate in spirits and relevant reactions.

PubMed

Aresta, M; Boscolo, M; Franco, D W

2001-06-01

The role of copper(II) species in the oxidation of inorganic cyanide to cyanate and in the conversion of cyanate or urea into ethyl carbamate was investigated. The oxidation process has been shown to be independent from the dissolved oxygen. Elemental analysis and infrared spectroscopy have shown the formation of a mixed copper carbonate/hydroxide in the process of oxidation of cyanide to cyanate in water/ethanol. The complexation to Cu(II) of cyanate formed upon cyanide oxidation makes the former more susceptible to nucleophilic attack from ethanol, with conversion into ethyl carbamate. Comparatively, urea has a minor role with respect to cyanide in the formation of ethyl carbamate. Therefore, the urea present in some samples of Brazilian sugar cane spirit (cachaça) has been shown to have almost no influence on the ethyl carbamate content of cachaças, which comes essentially from cyanide. Fe(II,III) affords results similar to those found with Cu(II). Some suggestions are presented to avoid ethyl carbamate formation in spirits during distillation.

Photoinduced, Copper-Catalyzed Carbon-Carbon Bond Formation with Alkyl Electrophiles: Cyanation of Unactivated Secondary Alkyl Chlorides at Room Temperature.

PubMed

Ratani, Tanvi S; Bachman, Shoshana; Fu, Gregory C; Peters, Jonas C

2015-11-04

We have recently reported that, in the presence of light and a copper catalyst, nitrogen nucleophiles such as carbazoles and primary amides undergo C-N coupling with alkyl halides under mild conditions. In the present study, we establish that photoinduced, copper-catalyzed alkylation can also be applied to C-C bond formation, specifically, that the cyanation of unactivated secondary alkyl chlorides can be achieved at room temperature to afford nitriles, an important class of target molecules. Thus, in the presence of an inexpensive copper catalyst (CuI; no ligand coadditive) and a readily available light source (UVC compact fluorescent light bulb), a wide array of alkyl halides undergo cyanation in good yield. Our initial mechanistic studies are consistent with the hypothesis that an excited state of [Cu(CN)2](-) may play a role, via single electron transfer, in this process. This investigation provides a rare example of a transition metal-catalyzed cyanation of an alkyl halide, as well as the first illustrations of photoinduced, copper-catalyzed alkylation with either a carbon nucleophile or a secondary alkyl chloride.

Carbamoylation correlates of cyanate neuropathy and cyanide poisoning: relevance to the biomarkers of cassava cyanogenesis and motor system toxicity.

PubMed

Kimani, Samuel; Moterroso, Victor; Lasarev, Mike; Kipruto, Sinei; Bukachi, Fred; Maitai, Charles; David, Larry; Tshala-Katumbay, Desire

2013-01-01

We sought to elucidate the protein carbamoylation patterns associated with cyanate neuropathy relative to cyanide poisoning. We hypothesized that under a diet deficient in sulfur amino acids (SAA), the carbamoylation pattern associated with cyanide poisoning is similar to that of cyanate neuropathy. Male rats (6-8 weeks old) were fed a diet with all amino acids (AAA) or 75%-deficiency in SAA and treated with 2.5 mg/kg/body weight (bw) NaCN, or 50 mg/kg/bw NaOCN, or 1 μl/g/bw saline, for up to 6 weeks. Albumin and spinal cord proteins were analyzed using liquid chromatography mass spectrometry (LC-MS/MS). Only NaOCN induced motor deficits with significant levels of carbamoylation. At Day 14, we found a diet-treatment interaction effect on albumin carbamoylation (p = 0.07). At Day 28, no effect was attributed to diet (p = 0.71). Mean number of NaCN-carbamoylated sites on albumin was 47.4% higher relative to vehicle (95% CI:16.7-86.4%). Only NaOCN carbamoylated spinal cord proteins, prominently, under SAA-restricted diet. Proteins targets included myelin basic and proteolipid proteins, neurofilament light and glial fibrillary acidic proteins, and 2', 3' cyclic-nucleotide 3'-phosphodiesterase. Under SAA deficiency, chronic but not acute cyanide toxicity may share biomarkers and pathogenetic similarities with cyanate neuropathy. Prevention of carbamoylation may protect against the neuropathic effects of cyanate.

Cyanate as energy source for nitrifiers

PubMed Central

Palatinszky, Marton; Herbold, Craig; Jehmlich, Nico; Pogoda, Mario; Han, Ping; von Bergen, Martin; Lagkouvardos, Ilias; Karst, Søren M.; Galushko, Alexander; Koch, Hanna; Berry, David; Daims, Holger; Wagner, Michael

2015-01-01

Ammonia- and nitrite-oxidizers are collectively responsible for the aerobic oxidation of ammonia via nitrite to nitrate and play essential roles for the global biogeochemical nitrogen cycle. The physiology of these nitrifying microbes has been intensively studied since the first experiments of Sergei Winogradsky more than a century ago. Urea and ammonia are the only recognized energy sources that promote the aerobic growth of ammonia-oxidizing bacteria and archaea. Here we report the aerobic growth of a pure culture of the ammonia-oxidizing thaumarchaeote Nitrososphaera gargensis1 on cyanate as the sole source of energy and reductant, the first organism known to do so. Cyanate, which is a potentially important source of reduced nitrogen in aquatic and terrestrial ecosystems2, is converted to ammonium and CO2 by this archaeon using a cyanase that is induced upon addition of this compound. Within the cyanase gene family, this cyanase is a member of a distinct clade that also contains cyanases of nitrite-oxidizing bacteria of the genus Nitrospira. We demonstrate by co-culture experiments that these nitrite-oxidizers supply ammonia-oxidizers lacking cyanase with ammonium from cyanate, which is fully nitrified by this consortium through reciprocal feeding. Screening of a comprehensive set of more than 3,000 publically available metagenomes from environmental samples revealed that cyanase-encoding genes clustering with the cyanases of these nitrifiers are widespread in the environment. Our results demonstrate an unexpected metabolic versatility of nitrifying microbes and suggest a previously unrecognized importance of cyanate for N-cycling in the environment. PMID:26222031

Decarbonylative Cross-Couplings: Nickel Catalyzed Functional Group Interconversion Strategies for the Construction of Complex Organic Molecules.

PubMed

Guo, Lin; Rueping, Magnus

2018-05-15

The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C-H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel-mediated decarbonylation process of esters and proposed a reaction mechanism involving a C(acyl)-O bond cleavage and a CO extrusion. Key nickel intermediates were isolated and characterized by Shi and co-workers, supporting the assumption of a nickel/ N-heterocyclic carbene-promoted C(acyl)-O bond activation and functionalization. Our combined experimental and computational study of a ligand-controlled chemoselective nickel-catalyzed cross-coupling of aromatic esters with alkylboron reagents provided further insight into the reaction mechanism. We demonstrated that nickel complexes with bidentate ligands favor the C(aryl)-C bond cleavage in the oxidative addition step, resulting in decarbonylative alkylations, while nickel complexes with monodentate phosphorus ligands promote the activation of the C(acyl)-O bond, leading to the production of ketone products. Although more detailed mechanistic investigations need to be undertaken, the successful development of decarbonylative cross-coupling reactions can serve as a solid foundation for future studies. We believe that this type of decarbonylative cross-coupling reactions will be of significant value, in particularly in combination with the retrosynthetic analysis and synthesis of natural products and biologically active molecules. Thus, the presented ester substitution methods will pave the way for successful applications in the construction of complex frameworks by late-stage modification and functionalization of carboxylic acid derivatives.

KSC-08pd2656

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians finish replacing the protective cover over the Super Lightweight Interchangeable Carrier, or SLIC. The cover was removed to clean the carrier of contaminants found Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2643

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician uncovers the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2646

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians inspect areas of the Super Lightweight Interchangeable Carrier, or SLIC, for contamination. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2641

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the payload canister is moved on the floor for loading of the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2653

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the protective cover is being replaced on the Super Lightweight Interchangeable Carrier, or SLIC. The cover was removed to clean the carrier of contaminants found Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2645

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians inspect areas of the Super Lightweight Interchangeable Carrier, or SLIC, for contamination. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2655

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician works to replace the protective cover on the Super Lightweight Interchangeable Carrier, or SLIC. The cover was removed to clean the carrier of contaminants found Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2654

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician works to replace the protective cover on the Super Lightweight Interchangeable Carrier, or SLIC. The cover was removed to clean the carrier of contaminants found Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2657

NASA Image and Video Library

2008-09-18

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians finish replacing the protective cover over the Super Lightweight Interchangeable Carrier, or SLIC. The cover was removed to clean the carrier of contaminants found Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2642

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician begins uncovering the Super Lightweight Interchangeable Carrier, or SLIC. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

KSC-08pd2644

NASA Image and Video Library

2008-09-17

CAPE CANAVERAL, Fla. - In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians inspect areas of the Super Lightweight Interchangeable Carrier, or SLIC, for contamination. Contamination discovered Sept. 17 during preparations to deliver NASA's Hubble Space Telescope servicing payload to Launch Pad 39A will be removed. Cleanliness is extremely important for space shuttle Atlantis’ STS-125 mission to Hubble, and the teams have insured that the SLIC is ready to fly. The SLIC, which holds battery module assemblies for servicing of the Hubble Space Telescope on the STS-125 mission, is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The carrier is one of four being transferred to Launch Pad 39A. At the pad, the carriers will be loaded into Atlantis’ payload bay. Launch of Atlantis is targeted for Oct. 10. Photo credit: NASA/Jack Pfaller

Nano-Particle Enhanced Polymer Materials for Space Flight Applications

NASA Technical Reports Server (NTRS)

Criss, Jim M., Jr.; Powell, William D.; Connell, John W.; Stallworth-Bordain, Yemaya; Brown, Tracy R.; Mintz, Eric A.; Schlea, Michelle R.; Shofne, Meisha L.

2009-01-01

Recent advances in materials technology both in polymer chemistry and nano-materials warrant development of enhanced structures for space flight applications. This work aims to develop spacecraft structures based on polymer matrix composites (PMCs) that utilize these advancements.. Multi-wall carbon nano-tubes (MWCNTs) are expected ·to increase mechanical performance, lower coefficient of thermal expansion (CTE), increase electrical conductivity (mitigate electrostatic charge), increase thermal conductivity, and reduce moisture absorption of the resultant space structures. In this work, blends of MWCNTs with PETI-330 were prepared and characterized. The nano-reinforced resins were then resin transfer molded (RTM) into composite panels using M55J carbon fabric and compared to baseline panels fabricated from a cyanate ester (RS-3) or a polyimide (PETI-330) resin containing no MWCNTs. In addition, methods of pre-loading the fabric with the MWCNTs were also investigated. The effects of the MWCNTs on the resin processing properties and on the composite end-use properties were also determined.

NASA Tech Briefs, February 2008

NASA Technical Reports Server (NTRS)

2008-01-01

Topics discussed include: Optical Measurement of Mass Flow of a Two-Phase Fluid; Selectable-Tip Corrosion-Testing Electrochemical Cell; Piezoelectric Bolt Breakers and Bolt Fatigue Testers; Improved Measurement of B(sub 22) of Macromolecules in a Flow Cell; Measurements by a Vector Network Analyzer at 325 to 508 GHz; Using Light to Treat Mucositis and Help Wounds Heal; Increasing Discharge Capacities of Li-(CF)(sub n) Cells; Dot-in-Well Quantum-Dot Infrared Photodetectors; Integrated Microbatteries for Implantable Medical Devices; Oxidation Behavior of Carbon Fiber-Reinforced Composites; GIDEP Batching Tool; Generic Spacecraft Model for Real-Time Simulation; Parallel-Processing Software for Creating Mosaic Images; Software for Verifying Image-Correlation Tie Points; Flexcam Image Capture Viewing and Spot Tracking; Low-Pt-Content Anode Catalyst for Direct Methanol Fuel Cells; Graphite/Cyanate Ester Face Sheets for Adaptive Optics; Atomized BaF2-CaF7 for Better-Flowing Plasma-Spray Feedstock; Nanophase Nickel-Zirconium Alloys for Fuel Cells; Vacuum Packaging of MEMS With Multiple Internal Seal Rings; Compact Two-Dimensional Spectrometer Optics; and Fault-Tolerant Coding for State Machines.

Clustering of two genes putatively involved in cyanate detoxification evolved recently and independently in multiple fungal lineages

USDA-ARS?s Scientific Manuscript database

Fungi that have the enzymes cyanase and carbonic anhydrase show a limited capacity to detoxify cyanate, a fungicide employed by both plants and humans. Here, we describe a novel two-gene cluster that comprises duplicated cyanase and carbonic anhydrase copies, which we name the CCA gene cluster, trac...

Reduction of ferrate(VI) and oxidation of cyanate in a Fe(VI)-TiO2-UV-NCO- system.

PubMed

Winkelmann, Kurt; Sharma, Virender K; Lin, Yekaterina; Shreve, Katherine A; Winkelmann, Catherine; Hoisington, Laura J; Yngard, Ria A

2008-08-01

The aqueous photocatalytic degradation of cyanate (NCO(-)), which is a long-lived neurotoxin formed during the remediation of cyanide in industrial waste streams, was studied in the ferrate(VI)-UV-TiO2-NCO(-) system. Kinetics measurements of the photocatalytic reduction of ferrate(VI) were carried out as a function of [NCO(-)], [ferrate(VI)], [O(2)], light intensity (I(o)), and amount of TiO2 in suspensions at pH 9.0. The photocatalytic reduction rate of ferrate(VI) in the studied system can be expressed as -d[Fe(VI)]/dt=kI(o)(0.5) [NCO(-)] [TiO2]. The rate of photocatalytic oxidation of cyanate with ferrate(VI) was greater than the rate in the analogous system without ferrate(VI). The possibility of involvement of reactive ferrate(V) species for this enhancement was determined by studying the reactivity of ferrate(V) with NCO(-) in a homogeneous solution using a premix pulse radiolysis technique. The rate constant for the reaction of ferrate(V) and NCO(-) in alkaline medium was estimated to be (9.60+/-0.07) x 10(2) M(-1) s(-1), which is much slower than the ferrate(VI) self-decomposition reaction (k approximately 10(7) M(-1) s(-1)). An analysis of the kinetic data in the Fe(VI)-UV-TiO2-NCO(-) system suggests that ferrate(V) is not directly participating in the oxidation of cyanate. Possible reactions in the system are presented to explain results of ferrate(VI) reduction and oxidation of cyanate.

Memory deficits associated with sublethal cyanide poisoning relative to cyanate toxicity in rodents.

PubMed

Kimani, S; Sinei, K; Bukachi, F; Tshala-Katumbay, D; Maitai, C

2014-03-01

Food (cassava) linamarin is metabolized into neurotoxicants cyanide and cyanate, metabolites of which we sought to elucidate the differential toxicity effects on memory. Young 6-8 weeks old male rats were treated intraperitoneally with either 2.5 mg/kg body weight (bw) cyanide (NaCN), or 50 mg/kg bw cyanate (NaOCN), or 1 μl/g bw saline, daily for 6 weeks. Short-term and long-term memories were assessed using a radial arm maze (RAM) testing paradigm. Toxic exposures had an influence on short-term working memory with fewer correct arm entries (F(2, 19) = 4.57 p < 0.05), higher working memory errors (WME) (F(2, 19) = 5.09, p < 0.05) and longer RAM navigation time (F(2, 19) = 3.91, p < 0.05) for NaOCN relative to NaCN and saline treatments. The long-term working memory was significantly impaired by cyanide with fewer correct arm entries (F(2, 19) = 7.45, p < 0.01) and increased working memory errors (F(2, 19) = 9.35 p < 0.05) in NaCN relative to NaOCN or vehicle treated animals. Reference memory was not affected by either cyanide or cyanate. Our study findings provide an experimental evidence for the biological plausibility that cassava cyanogens may induce cognition deficits. Differential patterns of memory deficits may reflect the differences in toxicity mechanisms of NaOCN relative to NaCN. Cognition deficits associated with cassava cyanogenesis may reflect a dual toxicity effect of cyanide and cyanate.

Memory deficits associated with sublethal cyanide poisoning relative to cyanate toxicity in rodents

PubMed Central

Kimani, S.; Sinei, K.; Bukachi, F.; Tshala-Katumbay, D.; Maitai, C.

2014-01-01

Background Food (cassava) linamarin is metabolized into neurotoxicants cyanide and cyanate, metabolites of which we sought to elucidate the differential toxicity effects on memory. Methods Young 6-8 weeks old male rats were treated intraperitoneally with either 2.5 mg/kg body weight (bw) cyanide (NaCN), or 50 mg/kg bw cyanate (NaOCN), or 1 μl/g bw saline, daily for 6 weeks. Short-term and long-term memories were assessed using a radial arm maze (RAM) testing paradigm. Results Toxic exposures had an influence on short-term working memory with fewer correct arm entries (F 2, 19 = 4.57 p <0.05), higher working memory errors (WME) (F 2, 19 = 5.09, p <0.05) and longer RAM navigation time (F2, 19 = 3.91, p <0.05) for NaOCN relative to NaCN and saline treatments. The long-term working memory was significantly impaired by cyanide with fewer correct arm entries (F 2, 19 = 7.45, p <0.01) and increased working memory errors (F 2, 19 = 9.35 p <0.05) in NaCN relative to NaOCN or vehicle treated animals. Reference memory was not affected by either cyanide or cyanate. Conclusion Our study findings provide an experimental evidence for the biological plausibility that cassava cyanogens may induce cognition deficits. Differential patterns of memory deficits may reflect the differences in toxicity mechanisms of NaOCN relative to NaCN. Cognition deficits associated with cassava cyanogenesis may reflect a dual toxicity effect of cyanide and cyanate. PMID:24293006

Crystal structure of poly[[μ-4-(hy-droxy-meth-yl)pyridine-κ(2) N:O][4-(hy-droxy-meth-yl)pyridine-κN](μ-thio-cyanato-κ(2) N:S)(thio-cyanato-κN)cadmium].

PubMed

Werner, Julia; Jess, Inke; Näther, Christian

2015-06-01

The crystal structure of the title compound, [Cd(NCS)2(C6H7NO)2] n is made up of Cd(2+) cations that are coordinated by three thio-cyanate ligands and three 4-(hy-droxy-meth-yl)pyridine ligands within distorted N4OS octa-hedra. The asymmetric unit consists of one Cd(2+) cation, two thio-cyanate anions and two 4-(hy-droxy-meth-yl)pyridine ligands in general positions. Two Cd(2+) cations are linked by two μ-1,3 N- and S-bonding thio-ycanate anions into dimers which are further linked into branched chains along [100] by two μ-1,6 N- and O-bonding 4-(hy-droxy-meth-yl)pyridine ligands. One additional N-bonded 4-(hy-droxy-meth-yl)pyridine ligand and one additional N-bonded thio-cyanate anion are only terminally bonded to the metal cation. Inter-chain O-H⋯S hydrogen bonds between the hy-droxy H atoms and one of the thio-cyanate S atoms connect the chains into a three-dimensional network.

Bioactivation of cyanide to cyanate in sulfur amino acid deficiency: relevance to neurological disease in humans subsisting on cassava.

PubMed

Tor-Agbidye, J; Palmer, V S; Lasarev, M R; Craig, A M; Blythe, L L; Sabri, M I; Spencer, P S

1999-08-01

Neurological disorders have been reported from parts of Africa with protein-deficient populations and attributed to cyanide (CN-) exposure from prolonged dietary use of cassava, a cyanophoric plant. Cyanide is normally metabolized to thiocyanate (SCN-) by the sulfur-dependent enzyme rhodanese. However, in protein-deficient subjects where sulfur amino acids (SAA) are low, CN may conceivably be converted to cyanate (OCN-), which is known to cause neurodegenerative disease in humans and animals. This study investigates the fate of potassium cyanide administered orally to rats maintained for up to 4 weeks on either a balanced diet (BD) or a diet lacking the SAAs, L-cystine and L-methionine. In both groups, there was a time-dependent increase in plasma cyanate, with exponential OCN- increases in SAA-deficient rats. A strongly positive linear relationship between blood CN- and plasma OCN- concentrations was observed in these animals. These data are consistent with the hypothesis that cyanate is an important mediator of chronic cyanide neurotoxicity during protein-calorie deficiency. The potential role of thiocyanate in cassava-associated konzo is discussed in relationship to the etiology of the comparable pattern of motor-system disease (spastic paraparesis) seen in lathyrism.

Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

PubMed Central

Wang, Liang; Wang, Guoxiong; Zhang, Jian; Bian, Chaoqun; Meng, Xiangju; Xiao, Feng-Shou

2017-01-01

The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds. PMID:28504259

Microcracking of Materials for Space

NASA Technical Reports Server (NTRS)

Brown, Timothy L.

1998-01-01

The effect of thermal-cycling-induced microcracking in fiber-reinforced polymer matrix composites is studied. Specific attention is focused on microcrack density as a function of the number of thermal cycles, and the effect of microcracking on the dimensional stability of composite materials. Changes in laminate coefficient of thermal expansion (CTE) and laminate stiffness are of primary concern. Included in the study are materials containing four different Thornel fiber types: a PAN-based T50 fiber and three pitch-based fibers, P55, P75, and P120. The fiber stiffnesses range from 55 Msi to 120 Msi. The fiber CTE's range from -0.50 x 1O(exp -6)/degrees F to -0.80 x 10(exp -6)/degrees F. Also included are three matrix types: Fiberite's 934 epoxy, Amoco's ERL1962 toughened epoxy, and YLA's RS3 cyanate ester. The lamination sequences of the materials considered include a cross-ply configuration, [0/90](sub 2s), and two quasi-isotropic configurations, [0/+45/-45/90](sub s), and [0/+45/90/-45](sub s). The layer thickness of the materials range from a nominal 0.001 in. to 0.005 in. In addition to the variety of materials considered, three different thermal cycling temperature ranges are considered. These temperature ranges are +/-250 degrees F, +/-l5O degrees F, and +/-50 degrees F. The combination of these material and geometric parameters and temperature ranges, combined with thermal cycling to thousands of cycles, makes this one of the most comprehensive studies of thermal-cycling-induced microcracking to date. Experimental comparisons are presented by examining the effect of layer thickness, fiber type, matrix type, and thermal cycling temperature range on microcracking and its influence on the laminates. Results regarding layer thickness effects indicate that thin-layer laminates microcrack more severely than identical laminates with thick layers. For some specimens in this study, the number of microcracks in thin-layer specimens exceeds that in thick-layer specimens by more than a factor of two. Despite the higher number of microcracks in the thin-layer specimens, small changes in CTE after thousands of cycles indicate that the thin-layer specimens are relatively unaffected by the presence of these cracks compared to the thick-layer specimens. Results regarding fiber type indicate that the number of microcracks and the change in CTE after thousands of cycles in the specimens containing PAN-based fibers are less than in the specimens containing comparable stiffness pitch-based fibers. Results for specimens containing the different pitch-based fibers indicate that after thousands of cycles, the number of microcracks in the specimens does not depend on the modulus or CTE of the fiber. The change in laminate CTE does, however, depend highly on the stiffness and CTE of the fiber. Fibers with higher stiffness and more negative CTE exhibit the lowest change in laminate CTE as a result of thermal cycling. The overall CTE of these specimens is, however, more negative as a result of the more negative CTE of the fiber. Results regarding matrix type based on the +/-250 degree F temperature range indicate that the RS3 cyanate ester resin system exhibits the greatest resistance to microcracking and the least change in CTE, particularly for cycles numbering 3000 and less. Extrapolations to higher numbers of cycles indicate, however, that the margin of increased performance is expected to decrease with additional thermal cycling. Results regarding thermal cycling temperature range depend on the matrix type considered and the layer thickness of the specimens. For the ERL1962 resin system, microcrack saturation is expected to occur in all specimens, regardless of the temperature range to which the specimens are exposed. By contrast, the RS3 resin system demonstrates a threshold effect such that cycled to less severe temperature ranges, microcracking does not occur. For the RS3 specimens with 0.005 in. layer thickness, no microcracking or changes in CTE are observed in specimens cycled between +/-150 degree F or +/- 50 degree F. For the RS3 specimens with 0.002 in. layer thickness, no microcracking or changes in CTE are observed in specimens cycled between +/-50 degree F. Results regarding laminate stiffness indicate negligible change in laminate stiffness due to thermal cycling for the materials and geometries considered in this investigation. The study includes X-ray examination of the specimens, showing that cracks observed at the edge of the specimens penetrate the entire width of the specimen. Glass transition temperatures of the specimens are measured, showing that resin chemistry is not altered as a result of thermal cycling. Results are also presented based on a one-dimensional shear lag analysis developed in the literature. The analysis requires material property information that is difficult to obtain experimentally. Using limited data from the present investigation, material properties associated with the analysis are modified to obtain reasonable agreement with measured microcrack densities. Based on these derived material properties, the analysis generally overpredicts the change in laminate CTE. Predicted changes in laminate stiffness show reasonable correlation with experimentally measured values.

Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawler, Katherine

2009-01-01

The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions canmore » be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may be the cause of the viscosity reduction. The flow behavior of alumina particles in water and BECy is markedly different. Aqueous alumina suspensions are shear thinning at all alumina loadings and capable of 50 vol% loading before losing fluidity whereas BECy/alumina suspensions show Newtonian behavior up to 5 vol%, and above 5 vol% show shear thinning at all shear rates. Highly loaded suspensions (i.e. 20vol% alumina) exhibit shear thinning at low and moderate shear rates and shear thickening at higher shear rates. The maximum particle loading for a fluid suspension, in this case, appears to be about 20 vol%. The difference in the viscosity of these suspensions must be related to the solvent-particle interactions for each system. The reason is not exactly known, but there are some notable differences between BECy and water. Water molecules are {approx}0.28 nm in length and highly hydrogen bonded with a low viscosity (1 mPa's) whereas in the cyanate ester (BECy) system, the solvent molecule is about 1.2 nm, in the largest dimension, with surfaces of varied charge distribution throughout the molecule. The viscosity of the monomer is also reasonably low for organic polymer precursor, about 7 mPa's. Nanoparticles in water tend to agglomerate and form flocs which are broken with the shear force applied during viscosity measurement. The particle-particle interaction is very important in this system. In BECy, the particles appear to be well dispersed and not as interactive. The solvent-particle interaction appears to be most important. It is not known exactly how the alumina particles interact with the monomer, but NMR suggests hydrogen bonding. These hydrogen bonds between the particle and monomer could very well affect the viscosity. A conclusion that can be reached in this work is that the presence of hydroxyl groups on the surface of the alumina particles is significant and seems to affect the interactions between other particles and the solvent. Thus, the hydrogen bonding between particles, particle/additive and/or particle/solvent dictates the behavior of nanosized alumina particle suspensions. The addition of dispersants can change the particle interactions and hence reduce the suspension viscosity. This was demonstrated with saccharides in the aqueous system and with benzoic acid in suspensions with BECy.« less

Palladium-Catalyzed, Copper(I)-Mediated Coupling of Boronic Acids and Benzylthiocyanate. A Cyanide-Free Cyanation of Boronic Acids

PubMed Central

Zhang, Zhihui; Liebeskind, Lanny S.

2008-01-01

A new method for the synthesis of nitriles is described. As a complement to the classic cyanation of aryl halides using cyanide sources and a transition metal catalyst, the palladium-catalyzed cross-coupling of thiocyanates with boronic acids in the presence of copper(I) thiophene-2-carboxylate (CuTC) affords nitriles in good to excellent yields. PMID:16956219

Crystal structure of N,N,N′,N′,N′′,N′′-hexa­methyl­guanidinium cyanate 1.5-hydrate

PubMed Central

Tiritiris, Ioannis; Kantlehner, Willi

2015-01-01

The title hydrated salt, C7H18N3 +·OCN−.1.5H2O, was synthesized starting from N,N,N′,N′,N′′,N′′-hexa­methyl­guanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water mol­ecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidin­ium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H⋯N hydrogen bonds between the crystal water mol­ecules and the cyanate ions and strong O—H⋯O hydrogen bonds between the water mol­ecules are present, resulting in a two-dimensional hydrogen bonded network running parallel to the (001) plane. The hexa­methyl­guanidinium ions are packed in between the layers built up by water mol­ecules and cyanate ions. PMID:26870506

Fiber-Level Modeling of Dynamic Strength of Kevlar (registered trademark) KM2 Ballistic Fabric

DTIC Science & Technology

2012-07-01

Ballistic-Performance Optimization of a Hybrid Carbon - Nanotube /E-glass Reinforced Poly-Vinyl-Ester-Epoxy-Matrix Com- posite Armor, J. Mater. Sci...2007, 42, p 5347–5359 4. M. Grujicic, W.C. Bell, L.L. Thompson, K.L. Koudela, and B.A. Cheeseman, Ballistic-Protection Performance of Carbon - Nanotube ...Armor via the Use of a Carbon - Nanotube Forest-Mat Strike Face, Mater. Des. Appl., 2008, 222, p 15–28 6. Y. Wang and X. Sun, Determining the Geometry

Flammability and Photo-Stability of Selected Polymer Systems

NASA Technical Reports Server (NTRS)

Lo, Jeelin

1981-01-01

A systematic approach to the improvement of the flammability of epoxy resins, bisphenol-A polycarbonate poly(butylene terephthalate), and Nylon 6.6 by introducing halogens and loop functionality into the flame retardants is described. The phthalides (the loop functionality containing molecules) include 3,3-bis(4-bromophenyl)-phthalide, 3,3-bis(4-chlorophenyl)phthalide, and phenolphthalein. The phthalide containing epoxy resins are synthesized and characterized in comparison with the bisphenol-A epoxy resins in terms of flammability in the copolymer systems. The resins include diglycidyl ethers of phenolphthalein, bisphenol-A. tetrabromobisphenol-A, and tetraoromophenolphthalein. The vaporization of the phthalide additive in the polymers is observed in Thermal Gravimetric Analysis. The flame retardancy is primarily due to the presence of halogens. In the poly(butylene terephthalate) system, the cleavage of the C(sub aromatic) -B bond of the flame retardant additive enhances the crosslinking react ions between the aromatic rings resulting in an increase of char formation. In the epoxy resin systems, loop functionality contributes to char formation to a larger extent. The interaction between the epoxy resin and poly-(butylene terephthalate) follows the mechanism of insertion of the oxirane ring into the ester bond. This mechanism is studied by FT-IR. The investigation of the thermal properties of the char-forming phenol-formaldehyde resins is conducted to provide information for the systematic design of high temperature flame-resistant phenolics. NMR and FT-IR are used to characterize the oligomeric resins and the cured resins. The curing agents used in the study include formaldehyde, s-trioxane and terephthaloyl chloride. The brominated phenolic resins are found to have higher oxygen indices with lower char yields.

KSC-08pd2088

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. – CAPE CANAVERAL, Fla. – In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers from NASA's Goddard Space Flight Center mate the Hubble vertical platform to the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2098

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. -- In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a worker from NASA's Goddard Space Flight Center installs a pallet support strut on the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2097

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. -- In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a worker from NASA's Goddard Space Flight Center installs a pallet support strut on the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2089

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. – In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers from NASA's Goddard Space Flight Center secure the Hubble vertical platform to the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2096

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. -- In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a worker from NASA's Goddard Space Flight Center installs a pallet support strut on the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2094

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. -- In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers from NASA's Goddard Space Flight Center install the pallet support struts on the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2087

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. – In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers from NASA's Goddard Space Flight Center move the Hubble vertical platform toward the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope, to which it will be mated. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2085

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. – In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope, elevated at left, is ready to be mated to the Hubble vertical platform, at right. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2086

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. – In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, workers from NASA's Goddard Space Flight Center move the Hubble vertical platform toward the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope, to which it will be mated. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2095

NASA Image and Video Library

2008-07-21

CAPE CANAVERAL, Fla. -- In the high bay of the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a worker from NASA's Goddard Space Flight Center documents the installation of a pallet support strut on the Super Lightweight Interchangeable Carrier for the Hubble Space Telescope. The Super Lightweight Interchangeable Carrier, or SLIC, is one of four carriers supporting hardware for space shuttle Atlantis' STS-125 mission to service the telescope. SLIC is built with state-of-the-art, lightweight, composite materials - carbon fiber with a cyanate ester resin and a titanium metal matrix composite. These composites have greater strength-to-mass ratios than the metals typically used in spacecraft design. The Orbital Replacement Unit Carrier, or ORUC, and the Flight Support System, or FSS, have also arrived at Kennedy. The Multi-Use Lightweight Equipment carrier will be delivered in early August. The carriers will be prepared for the integration of telescope science instruments, both internal and external replacement components, as well as the flight support equipment to be used by the astronauts during the Hubble servicing mission, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

Performance assessment of 700-bar compressed hydrogen storage for light duty fuel cell vehicles

DOE PAGES

Hua, Thanh Q.; Roh, Hee-Seok; Ahluwalia, Rajesh K.

2017-09-11

In this study, type 4 700-bar compressed hydrogen storage tanks were modeled using ABAQUS. The finite element model was first calibrated against data for 35-L subscale test tanks to obtain the composite translation efficiency, and then applied to full sized tanks. Two variations of the baseline T700/epoxy composite were considered in which the epoxy was replaced with a low cost vinyl ester resin and low cost resin with an alternate sizing. The results showed that the reduction in composite weight was attributed primarily to the lower density of the resin and higher fiber volume fraction in the composite due tomore » increased squeeze-out with the lower viscosity vinyl ester resin. The system gravimetric and volumetric capacities for the onboard storage system that holds 5.6 kg H 2 are 4.2 wt% (1.40 kWh/kg) and 24.4 g-H 2/L (0.81 kWh/L), respectively. The system capacities increase and carbon fiber requirement decreases if the in-tank amount of unrecoverable hydrogen is reduced by lowering the tank "empty" pressure. Models of an alternate tank design showed potential 4-7% saving in composite usage for tanks with a length-to-diameter (L/D) ratio of 2.8-3.0 but no saving for L/D of 1.7. Lastly, a boss with smaller opening and longer flange does not appear to reduce the amount of helical windings.« less

Synthesis of Polyformate Esters of Vegetable Oils: Milkweed, Pennycress, and Soy.

PubMed

Harry-O'kuru, Rogers E; Biresaw, Girma; Tisserat, Brent; Evangelista, Roque

2016-01-01

In a previous study of the characteristics of acyl derivatives of polyhydroxy milkweed oil (PHMWO), it was observed that the densities and viscosities of the respective derivatives decreased with increased chain length of the substituent acyl group. Thus from the polyhydroxy starting material, attenuation in viscosity of the derivatives relative to PHMWO was found in the order: PHMWO ≫ PAcMWE ≫ PBuMWE ≫ PPMWE (2332 : 1733 : 926.2 : 489.4 cSt, resp., at 40°C), where PAcMWE, PBuMWE, and PPMWE were the polyacetyl, polybutyroyl, and polypentanoyl ester derivatives, respectively. In an analogous manner, the densities also decreased as the chain length increased although not as precipitously compared to the viscosity drop. By inference, derivatives of vegetable oils with short chain length substituents on the triglyceride would be attractive in lubricant applications in view of their higher densities and possibly higher viscosity indices. Pursuant to this, we have explored the syntheses of formyl esters of three vegetable oils in order to examine the optimal density, viscosity, and related physical characteristics in relation to their suitability as lubricant candidates. In the absence of ready availability of formic anhydride, we opted to employ the epoxidized vegetable oils as substrates for formyl ester generation using glacial formic acid. The epoxy ring-opening process was smooth but was apparently followed by a simultaneous condensation reaction of the putative α-hydroxy formyl intermediate to yield vicinal diformyl esters from the oxirane. All three polyformyl esters milkweed, soy, and pennycress derivatives exhibited low coefficient of friction and a correspondingly much lower wear scar in the 4-ball antiwear test compared to the longer chain acyl analogues earlier studied.

Synthesis of Polyformate Esters of Vegetable Oils: Milkweed, Pennycress, and Soy

PubMed Central

Harry-O'kuru, Rogers E.; Biresaw, Girma; Tisserat, Brent; Evangelista, Roque

2016-01-01

In a previous study of the characteristics of acyl derivatives of polyhydroxy milkweed oil (PHMWO), it was observed that the densities and viscosities of the respective derivatives decreased with increased chain length of the substituent acyl group. Thus from the polyhydroxy starting material, attenuation in viscosity of the derivatives relative to PHMWO was found in the order: PHMWO ≫ PAcMWE ≫ PBuMWE ≫ PPMWE (2332 : 1733 : 926.2 : 489.4 cSt, resp., at 40°C), where PAcMWE, PBuMWE, and PPMWE were the polyacetyl, polybutyroyl, and polypentanoyl ester derivatives, respectively. In an analogous manner, the densities also decreased as the chain length increased although not as precipitously compared to the viscosity drop. By inference, derivatives of vegetable oils with short chain length substituents on the triglyceride would be attractive in lubricant applications in view of their higher densities and possibly higher viscosity indices. Pursuant to this, we have explored the syntheses of formyl esters of three vegetable oils in order to examine the optimal density, viscosity, and related physical characteristics in relation to their suitability as lubricant candidates. In the absence of ready availability of formic anhydride, we opted to employ the epoxidized vegetable oils as substrates for formyl ester generation using glacial formic acid. The epoxy ring-opening process was smooth but was apparently followed by a simultaneous condensation reaction of the putative α-hydroxy formyl intermediate to yield vicinal diformyl esters from the oxirane. All three polyformyl esters milkweed, soy, and pennycress derivatives exhibited low coefficient of friction and a correspondingly much lower wear scar in the 4-ball antiwear test compared to the longer chain acyl analogues earlier studied. PMID:26955488

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Shunmin; Tian, Chengcheng; Zhu, Xiang

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed in this paper to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. Finally, the catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

catena-Poly[(E)-4,4′-(ethane-1,2-di­yl)dipyridinium [[bis­(thio­cyanato-κN)ferrate(II)]-di-μ-thio­cyanato-κ2 N:S;κ2 S:N

PubMed Central

Wöhlert, Susanne; Jess, Inke; Näther, Christian

2011-01-01

In the crystal structure of the title compound, {(C12H14N2)[Fe(NCS)4]}n, the iron(II) cation is coordinated by four N-bonded and two S-bonded thio­cyanate anions in a distorted octa­hedral coordination mode. The asymmetric unit consists of half an iron(II) cation and half a protonated (E)-4,4′-(ethane-1,2-di­yl)dipyridinium dication, each located on a centre of inversion. In addition, there are two thio­cyanate anions in general positions. The crystal structure consists of Fe—(NCS)2—Fe chains in which each iron(II) cation is additionally coordinated by two terminal N-bonded thio­cyanate anions. Non-coordinating dipyridinium dications are present between the thiocyanatoferrate(II) chains and are connected to the anions via N—H⋯N and N—H⋯S hydrogen-bond interactions. PMID:22219754

catena-Poly[(E)-4,4′-(ethene-1,2-di­yl)dipyridinium [[bis­(thio­cyanato-κN)ferrate(II)]-di-μ-thio­cyanato-κ2 N:S;κ2 S:N

PubMed Central

Wöhlert, Susanne; Wriedt, Mario; Jess, Inke; Näther, Christian

2010-01-01

In the title compound, {(C12H12N2)[Fe(NCS)4]}n, each FeII cation is coordinated by four N-bonded and two S-bonded thio­cyanate anions in an octa­hedral coordination mode. The asymmetric unit consists of one FeII cation, located on a center of inversion, as well as one protonated (E)-4,4′-(ethene-1,2-di­yl)dipyridinium dication and two thio­cyanate anions in general positions. The crystal structure consists of Fe—(NCS)2—Fe chains extending along the a axis, in which two further thio­cyanate anions are only terminally bonded via nitro­gen. Non-coordinating (E)-4,4′-(ethene-1,2-di­yl)dipyrid­inium cations are found between the chains. PMID:21587404

Clustering of two genes putatively involved in cyanate detoxification evolved recently and independently in multiple fungal lineages.

PubMed

Elmore, M Holly; McGary, Kriston L; Wisecaver, Jennifer H; Slot, Jason C; Geiser, David M; Sink, Stacy; O'Donnell, Kerry; Rokas, Antonis

2015-02-06

Fungi that have the enzymes cyanase and carbonic anhydrase show a limited capacity to detoxify cyanate, a fungicide employed by both plants and humans. Here, we describe a novel two-gene cluster that comprises duplicated cyanase and carbonic anhydrase copies, which we name the CCA gene cluster, trace its evolution across Ascomycetes, and examine the evolutionary dynamics of its spread among lineages of the Fusarium oxysporum species complex (hereafter referred to as the FOSC), a cosmopolitan clade of purportedly clonal vascular wilt plant pathogens. Phylogenetic analysis of fungal cyanase and carbonic anhydrase genes reveals that the CCA gene cluster arose independently at least twice and is now present in three lineages, namely Cochliobolus lunatus, Oidiodendron maius, and the FOSC. Genome-wide surveys within the FOSC indicate that the CCA gene cluster varies in copy number across isolates, is always located on accessory chromosomes, and is absent in FOSC's closest relatives. Phylogenetic reconstruction of the CCA gene cluster in 163 FOSC strains from a wide variety of hosts suggests a recent history of rampant transfers between isolates. We hypothesize that the independent formation of the CCA gene cluster in different fungal lineages and its spread across FOSC strains may be associated with resistance to plant-produced cyanates or to use of cyanate fungicides in agriculture. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Selection of Lipases for the Synthesis of Biodiesel from Jatropha Oil and the Potential of Microwave Irradiation to Enhance the Reaction Rate

PubMed Central

2016-01-01

The present study deals with the enzymatic synthesis of biodiesel by transesterification of Jatropha oil (Jatropha curcas L.) with ethanol in a solvent-free system. Seven commercial lipase preparations immobilized by covalent attachment on epoxy-polysiloxane-polyvinyl alcohol composite (epoxy-SiO2-PVA) were tested as biocatalysts. Among them, immobilized lipases from Pseudomonas fluorescens (lipase AK) and Burkholderia cepacia (lipase PS) were the most active biocatalysts in biodiesel synthesis, reaching ethyl ester yields (FAEE) of 91.1 and 98.3% at 72 h of reaction, respectively. The latter biocatalyst exhibited similar performance compared to Novozym® 435. Purified biodiesel was characterized by different techniques. Transesterification reaction carried out under microwave irradiation exhibited higher yield and productivity than conventional heating. The operational stability of immobilized lipase PS was determined in repeated batch runs under conventional and microwave heating systems, revealing half-life times of 430.4 h and 23.5 h, respectively. PMID:27868060

Bis(2,3,5,6-tetra-2-pyridyl­pyrazine-κ3 N 2,N 1,N 6)nickel(II) dithio­cyanate dihydrate

PubMed Central

De la Pinta, Noelia; Fidalgo, M. Luz; Ezpeleta, José M.; Cortés, Roberto; Madariaga, Gotzon

2011-01-01

In the title compound, [Ni(C24H16N6)2](NCS)2·2H2O, the central NiII ion is octahedrally coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridyl­pyrazine ligands (tppz). Two thio­cyanate anions act as counter-ions and two water mol­ecules act as solvation agents. O—H⋯N hydrogen bonds are observed in the crystral structure. PMID:21522540

Optimization and Validation of a Surface Wipe Method to Determine Cyanide and Cyanate: Application to the Emergency Destruction System

DTIC Science & Technology

2012-08-01

NJ b WC-7 Grade 42, 55 mm filter paper Whatman, Piscataway, NJ b WC-8 Cellulose nitrate membrane filter, 47 mm Whatman, Piscataway, NJ b WC-9...density polypropylene plastic bottle. 2.5 Standards Sodium cyanide (NaCN, ≥97.0%, CAS no. 143-33-9) and potassium cyanate (KOCN, ≥97.0...Agilent Technologies model 3D CE system, with an ultraviolet (deuterium lamp) diode array detector, was used to determine the quantities of CN and OCN

Crystal structure of tetra-kis-[μ2-2-(di-methyl-amino)-ethano-lato-κ(3) N,O:O]di-μ3-hydroxido-di-thio-cyanato-κ(2) N-dichromium(III)dilead(II) di-thio-cyanate aceto-nitrile monosolvate.

PubMed

Rusanova, Julia A; Semenaka, Valentyna V; Omelchenko, Irina V

2016-04-01

The tetra-nuclear complex cation of the title compound, [Cr2Pb2(NCS)2(OH)2(C4H10NO)4](SCN)2·CH3CN, lies on an inversion centre. The main structural feature of the cation is a distorted seco-norcubane Pb2Cr2O6 cage with a central four-membered Cr2O2 ring. The Cr(III) ion is coordinated in a distorted octa-hedron, which involves two N atoms of one bidentate ligand and one thio-cyanate anion, two μ2-O atoms of 2-(di-methyl-amino)-ethano-late ligands and two μ3-O atoms of hydroxide ions. The coordination geometry of the Pb(II) ion is a distorted disphenoid, which involves one N atom, two μ2-O atoms and one μ3-O atom. In addition, weak Pb⋯S inter-actions involving the coordinating and non-coordinating thio-cyanate anions are observed. In the crystal, the complex cations are linked through the thio-cyanate anions via the Pb⋯S inter-actions and O-H⋯N hydrogen bonds into chains along the c axis. The chains are further linked together via S⋯S contacts. The contribution of the disordered solvent aceto-nitrile mol-ecule was removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] procedure in PLATON. The solvent is included in the reported mol-ecular formula, weight and density.

Adhesion promotion via noncovalent interactions in self-healing polymers.

PubMed

Wilson, Gerald O; Caruso, Mary M; Schelkopf, Stuart R; Sottos, Nancy R; White, Scott R; Moore, Jeffrey S

2011-08-01

Dimethylnorbornene ester (DNE) is successfully used as a noncovalent adhesion promoter. DNE was confirmed to copolymerize with dicyclopentadiene (DCPD) to yield a copolymer with better adhesion to an EPON 828 epoxy matrix relative to poly(DCPD) alone. The mechanical properties of the copolymer were comparable to that of poly(DCPD) alone. An optimized blend of the monomers was encapsulated using a urea-formaldheyde microencapsulation procedure and the resulting capsules were used for in situ self-healing experiments. Improved healing efficiency was observed for samples containing the DCPD/DNE capsules under conditions in which the monomers were efficiently polymerized.

Strong composition dependence of adhesive properties of ultraviolet curing adhesives with modified acrylates

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Li, Yandong; Wang, Fupeng; Peng, Cheng; Xu, Zhichao; Hu, Jianbing

2018-05-01

Ultraviolet (UV) curable adhesives have been widely researched in fields of health care and electronic components. UV curing systems with modified acrylic ester prepolymers have been frequently employed. In order to clarify composition dependence of adhesive properties of adhesives containing modified acrylates, in this work, several UV curing adhesives bearing urethane and epoxy acrylates were designed and fabricated. The effects of prepolymer, diluent, feed ratio, initiator and assistant on adhesive performances were investigated. This work might offer a facile route to gain promising high-performance UV curable adhesives with desired adhesive traits through regulating their compositions.

Poly(ester urea)-Based Adhesives: Improved Deployment and Adhesion by Incorporation of Poly(propylene glycol) Segments.

PubMed

Zhou, Jinjun; Bhagat, Vrushali; Becker, Matthew L

2016-12-14

The adhesive nature of mussels arises from the catechol moiety in the 3,4-dihydroxyphenylalanine (DOPA) amino acid, one of the many proteins that contribute to the unique adhesion properties of mussels. Inspired by these properties, many biomimetic adhesives have been developed over the past few years in an attempt to replace adhesives such as fibrin, cyanoacrylate, and epoxy glues. In the present work, we synthesized ethanol soluble but water insoluble catechol functionalized poly(ester urea) random copolymers that help facilitate delivery and adhesion in wet environments. Poly(propylene glycol) units incorporated into the polymer backbone impart ethanol solubility to these polymers, making them clinically relevant. A catechol to cross-linker ratio of 10:1 with a curing time of 4 h exceeded the performance of commercial fibrin glue (4.8 ± 1.4 kPa) with adhesion strength of 10.6 ± 2.1 kPa. These adhesion strengths are significant with the consideration that the adhesion studies were performed under wet conditions.

Palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate: A practical synthesis of unsymmetrical ureas

PubMed Central

Vinogradova, Ekaterina V.; Fors, Brett P.; Buchwald, Stephen L.

2012-01-01

An efficient method for palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate is reported. The protocol allows for the synthesis of unsymmetrical N,N'-di- and N,N,N'-trisubstituted ureas in one pot, and is tolerant of a wide range of functional groups. Insight into the mechanism of aryl isocyanate formation is gleaned through studies of the transmetallation and reductive elimination steps of the reaction, including the first demonstration of reductive elimination from an arylpalladium isocyanate complex to produce an aryl isocyanate. PMID:22716197

Tris[4-(dimethyl­amino)­pyridinium] hexa­kis­(thio­cyanato-κN)ferrate(III) monohydrate

PubMed Central

Wöhlert, Susanne; Jess, Inke; Näther, Christian

2013-01-01

In the title compound, (C7H11N2)3[Fe(NCS)6]·H2O, the FeIII cation is coordinated by six terminal N-bonded thio­cyanate anions into a discrete threefold negatively charged complex. Charge balance is achieved by three protonated 4-(dimethyl­amino)­pyridine cations. The asymmetric unit consists of one FeIII cation, six thio­cyanate anions, three 4-(dimethyl­amino)­pyridinium cations and one water mol­ecule, all of them located in general positions. PMID:23476331

Crystal structure of tetra­kis­[μ2-2-(di­methyl­amino)­ethano­lato-κ3 N,O:O]di-μ3-hydroxido-di­thio­cyanato-κ2 N-dichromium(III)dilead(II) di­thio­cyanate aceto­nitrile monosolvate

PubMed Central

Rusanova, Julia A.; Semenaka, Valentyna V.; Omelchenko, Irina V.

2016-01-01

The tetra­nuclear complex cation of the title compound, [Cr2Pb2(NCS)2(OH)2(C4H10NO)4](SCN)2·CH3CN, lies on an inversion centre. The main structural feature of the cation is a distorted seco-norcubane Pb2Cr2O6 cage with a central four-membered Cr2O2 ring. The CrIII ion is coordinated in a distorted octa­hedron, which involves two N atoms of one bidentate ligand and one thio­cyanate anion, two μ2-O atoms of 2-(di­methyl­amino)­ethano­late ligands and two μ3-O atoms of hydroxide ions. The coordination geometry of the PbII ion is a distorted disphenoid, which involves one N atom, two μ2-O atoms and one μ3-O atom. In addition, weak Pb⋯S inter­actions involving the coordinating and non-coordinating thio­cyanate anions are observed. In the crystal, the complex cations are linked through the thio­cyanate anions via the Pb⋯S inter­actions and O—H⋯N hydrogen bonds into chains along the c axis. The chains are further linked together via S⋯S contacts. The contribution of the disordered solvent aceto­nitrile mol­ecule was removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9–18] procedure in PLATON. The solvent is included in the reported mol­ecular formula, weight and density. PMID:27375871

Thermoset nanocomposites from waterborne bio-based epoxy resin and cellulose nanowhiskers.

PubMed

Wu, Guo-min; Liu, Di; Liu, Gui-feng; Chen, Jian; Huo, Shu-ping; Kong, Zhen-wu

2015-01-01

Thermoset nanocomposites were prepared from a waterborne terpene-maleic ester type epoxy resin (WTME) and cellulose nanowhiskers (CNWs). The curing behaviors of WTME/CNWs nanocomposites were measured with rotational rheometer. The results show that the storage modulus (G') of WTME/CNWs nanocomposites increased with the increase of CNWs content. Observations by scanning electron microscopy (SEM) demonstrate that the incorporation of CNWs in WTME matrix caused microphase separation and destroyed the compactness of the matrix. This effect leads to the glass transition temperatures (Tg) of WTME/CNWs nanocomposites slightly decrease with the increase of CNWs content, which were confirmed by both DSC and DMA tests. The mechanical properties of WTME/CNWs nanocomposites were investigated by tensile testing. The Yong's modulus (E) and tensile strength (σb) of the nanocomposites were significantly reinforced by the addition of CNWs. These results indicate that CNWs exhibit excellent reinforcement effect on WTME matrix, due to the formation and increase of interfacial interaction by hydrogen bonds between CNWs nano-filler and the WTME matrix. Copyright © 2015 Elsevier Ltd. All rights reserved.

Highly Modified Cellulose Nanocrystals and Formation of Epoxy-CNC Nanocomposites.

PubMed

Abraham, Eldho; Kam, Doron; Nevo, Yuval; Slattegard, Rikard; Rivkin, Amit; Lapidot, Shaul; Shoseyov, Oded

2016-10-05

This work presents an environmentally friendly, iodine-catalysed chemical modification method to generate highly hydrophobic, optically active cellulose nanocrystals (CNC). The high degree of ester substitution (DS=2.18), hydrophobicity, crystalline behaviour and optical activity of the generated acetylated CNC (Ac-CNC) were quantified by TEM, FTIR, solid 13C NMR, contact angle, XRD and POM analyses. Ac-CNC possessing substantial enhancement in thermal stability (16.8%) and forms thin films with interlayer distance of 50-150 nm, presenting cavities suitable for entrapping nano and micro particles. Generated Ac-CNC proved as an effective reinforcing agent in hydrophobic polymer matrices for fabricating high performance nanocomposites. When integrated at a very low weight percentage (0.5%) in an epoxy matrix, Ac-CNC provided for a 73% increase in tensile strength and a 98% increase in modulus, demonstrating its remarkable reinforcing potential and effective stress transfer behaviour. The method of modification and the unique properties of the modified CNC (hydrophobicity, crystallinity, reinforcing ability and optical activity) render them a novel bionanomaterial for a range of multipurpose applications.

Study Methods to Standardize Thermography NDE

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1998-01-01

The purpose of this work is to develop thermographic inspection methods and standards for use in evaluating structural composites and aerospace hardware. Qualification techniques and calibration methods are investigated to standardize the thermographic method for use in the field. Along with the inspections of test standards structural hardware, support hardware is designed and fabricated to aid in the thermographic process. Also, a standard operating procedure is developed for performing inspections with the Bales Thermal Image Processor (TIP). Inspections are performed on a broad range of structural composites. These materials include various graphite/epoxies, graphite/cyanide-ester, graphite/silicon-carbide, graphite phenolic and Keviar/epoxy. Also metal honeycomb (titanium and aluminum faceplates over an aluminum honeycomb core) structures are investigated. Various structural shapes are investigated and the thickness of the structures vary from as few as 3 plies to as many as 80 plies. Special emphasis is placed on characterizing defects in attachment holes and bondlines, in addition to those resulting from impact damage and the inclusion of foreign matter. Image processing through statistical analysis and digital filtering is investigated to enhance the quality and quantify the NDE thermal images when necessary.

Study Methods to Standardize Thermography NDE

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1998-01-01

The purpose of this work is to develop thermographic inspection methods and standards for use in evaluating structural composites and aerospace hardware. Qualification techniques and calibration methods are investigated to standardize the thermographic method for use in the field. Along with the inspections of test standards structural hardware, support hardware is designed and fabricated to aid in the thermographic process. Also, a standard operating procedure is developed for performing inspections with the Bales Thermal Image Processor (TIP). Inspections are performed on a broad range of structural composites. These materials include graphite/epoxies, graphite/cyanide-ester, graphite/silicon-carbide, graphite phenolic and Kevlar/epoxy. Also metal honeycomb (titanium and aluminum faceplates over an aluminum honeycomb core) structures are investigated. Various structural shapes are investigated and the thickness of the structures vary from as few as 3 plies to as many as 80 plies. Special emphasis is placed on characterizing defects in attachment holes and bondlines, in addition to those resulting from impact damage and the inclusion of foreign matter. Image processing through statistical analysis and digital filtering is investigated to enhance the quality and quantify the NDE thermal images when necessary.

General and practical formation of thiocyanates from thiols.

PubMed

Frei, Reto; Courant, Thibaut; Wodrich, Matthew D; Waser, Jerome

2015-02-02

A new method for the cyanation of thiols and disulfides using cyanobenziodoxol(on)e hypervalent iodine reagents is described. Both aliphatic and aromatic thiocyanates can be accessed in good yields in a few minutes at room temperature starting from a broad range of thiols with high chemioselectivity. The complete conversion of disulfides to thiocyanates was also possible. Preliminary computational studies indicated a low energy concerted transition state for the cyanation of the thiolate anion or radical. The developed thiocyanate synthesis has broad potential for various applications in synthetic chemistry, chemical biology and materials science. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Thermal Conductivity Polymer Matrix Composites (PMC) for Advanced Space Radiators

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Bowman, Cheryl; Beach, Duane

2007-01-01

High temperature polymer matrix composites (PMC) reinforced with high thermal conductivity (approx. 1000 W/mK) pitch-based carbon fibers are evaluated for a facesheet/fin structure of large space radiator systems. Significant weight reductions along with improved thermal performance, structural integrity and space durability toward its metallic counterparts were envisioned. Candidate commercial resin systems including Cyanate Esters, BMIs, and polyimide were selected based on thermal capabilities and processability. PMC laminates were designed to match the thermal expansion coefficient of various metal heat pipes or tubes. Large, but thin composite panels were successfully fabricated after optimizing cure conditions. Space durability of PMC with potential degradation mechanisms was assessed by simulated thermal aging tests in high vacuum, 1-3 x 10(exp -6) torr, at three temperatures, 227 C, 277 C, and 316 C for up to one year. Nanocomposites with vapor-grown carbon nano-fibers and exfoliated graphite flakes were attempted to improve thermal conductivity (TC) and microcracking resistance. Good quality nanocomposites were fabricated and evaluated for TC and durability including radiation resistance. TC was measured in both in-plan and thru-the-thickness directions, and the effects of microcracks on TC are also being evaluated. This paper will discuss the systematic experimental approaches, various performance-durability evaluations, and current subcomponent design and fabrication/manufacturing efforts.

Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods.

PubMed

Dalbouha, S; Senent, M L; Komiha, N; Domínguez-Gómez, R

2016-09-28

Various astrophysical relevant molecules obeying the empirical formula C 2 H 3 NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CH 3 NCO), methyl cyanate (CH 3 OCN), methyl fulminate (CH 3 ONC), and acetonitrile N-oxide (CH 3 CNO). A CH 3 CON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CH 3 CON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C 3v symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton.

Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods

NASA Astrophysics Data System (ADS)

Dalbouha, S.; Senent, M. L.; Komiha, N.; Domínguez-Gómez, R.

2016-09-01

Various astrophysical relevant molecules obeying the empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CH3NCO), methyl cyanate (CH3OCN), methyl fulminate (CH3ONC), and acetonitrile N-oxide (CH3CNO). A CH3CON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CH3CON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C3v symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton.

Cholesterol photo-oxidation: A chemical reaction network for kinetic modeling.

PubMed

Barnaba, Carlo; Rodríguez-Estrada, Maria Teresa; Lercker, Giovanni; García, Hugo Sergio; Medina-Meza, Ilce Gabriela

2016-12-01

In this work we studied the effect of polyunsaturated fatty acids (PUFAs) methyl esters on cholesterol photo-induced oxidation. The oxidative routes were modeled with a chemical reaction network (CRN), which represents the first application of CRN to the oxidative degradation of a food-related lipid matrix. Docosahexaenoic acid (DHA, T-I), eicosapentaenoic acid (EPA, T-II) and a mixture of both (T-III) were added to cholesterol using hematoporphyrin as sensitizer, and were exposed to a fluorescent lamp for 48h. High amounts of Type I cholesterol oxidation products (COPs) were recovered (epimers 7α- and 7β-OH, 7-keto and 25-OH), as well as 5β,6β-epoxy. Fitting the experimental data with the CRN allowed characterizing the associated kinetics. DHA and EPA exerted different effects on the oxidative process. DHA showed a protective effect to 7-hydroxy derivatives, whereas EPA enhanced side-chain oxidation and 7β-OH kinetic rates. The mixture of PUFAs increased the kinetic rates several fold, particularly for 25-OH. With respect to the control, the formation of β-epoxy was reduced, suggesting potential inhibition in the presence of PUFAs. Copyright © 2016 Elsevier Inc. All rights reserved.

Transnitrilation from Dimethylmalononitrile to Aryl Grignard and Lithium Reagents: A Practical Method for Aryl Nitrile Synthesis.

PubMed

Reeves, Jonathan T; Malapit, Christian A; Buono, Frederic G; Sidhu, Kanwar P; Marsini, Maurice A; Sader, C Avery; Fandrick, Keith R; Busacca, Carl A; Senanayake, Chris H

2015-07-29

An electrophilic cyanation of aryl Grignard or lithium reagents, generated in situ from the corresponding aryl bromides or iodides, by a transnitrilation with dimethylmalononitrile (DMMN) was developed. DMMN is a commercially available, bench-stable solid. The transnitrilation with DMMN avoids the use of toxic reagents and transition metals and occurs under mild reaction conditions, even for extremely sterically hindered substrates. The transnitrilation of aryllithium species generated by directed ortho-lithiation enabled a net C-H cyanation. The intermediacy of a Thorpe-type imine adduct in the reaction was supported by isolation of the corresponding ketone from the quenched reaction. Computational studies supported the energetic favorability of retro-Thorpe fragmentation of the imine adduct.

Myeloperoxidase-derived chlorinating species induce protein carbamylation through decomposition of thiocyanate and urea: Novel pathways generating dysfunctional high-density lipoprotein

PubMed Central

Holzer, Michael; Zangger, Klaus; El-Gamal, Dalia; Binder, Veronika; Curcic, Sanja; Konya, Viktoria; Schuligoi, Rufina; Heinemann, Akos; Marsche, Gunther

2013-01-01

Aim Protein carbamylation through cyanate is thought to have a causal role in promoting cardiovascular disease. We recently observed that the phagocyte protein myeloperoxidase (MPO) specifically induces high-density lipoprotein carbamylation, rather than chlorination, in human atherosclerotic lesions, raising the possibility that MPO-derived chlorinating species are involved in cyanate formation. Results Here we show that MPO-derived chlorinating species rapidly decompose the plasma components thiocyanate and urea thereby promoting (lipo)protein carbamylation. Strikingly, the presence of physiologic concentrations of thiocyanate completely prevented MPO-induced 3-chlorotyrosine formation in HDL. Moreover, thiocyanate scavenged a 2.5-fold molar excess of hypochlorous acid, promoting HDL carbamylation, but not chlorination. Carbamylation of HDL resulted in a loss of anti-inflammatory and anti-oxidative properties. Cyanate significantly impaired (i) HDL’s ability to activate lecithin-cholesterol acyltransferase, (ii) the activity of paraoxonase, a major HDL-associated anti-inflammatory enzyme and (iii) the anti-oxidative activity of HDL. Innovation Here we report that MPO-derived chlorinating species preferentially induce protein carbamylation - rather than chlorination - in the presence of physiologically relevant thiocyanate concentrations. Carbamylation of HDL results in the loss of its anti-inflammatory and anti-oxidative activities. Conclusion MPO-mediated decomposition of thiocyanate and/or urea might be a relevant mechanism for generating dysfunctional HDL in human disease. PMID:22462773

Crystal structure of octa-kis-(4-meth-oxy-pyridinium) bis-(4-meth-oxy-pyridine-κN)tetra-kis-(thio-cyanato-κN)ferrate(III) bis-[(4-meth-oxypyri-dine-κN)pentakis-(thio-cyanato-κN)ferrate(III)] hexa-kis-(thio-cyanato-κN)ferrate(III) with iron in three different octa-hedral coordination environments.

PubMed

Jochim, Aleksej; Jess, Inke; Näther, Christian

2018-03-01

The crystal structure of the title salt, (C 6 H 8 NO) 8 [Fe(NCS) 4 (C 6 H 7 NO) 2 ][Fe(NCS) 5 (C 6 H 7 NO)] 2 [Fe(NCS) 6 ], comprises three negatively charged octa-hedral Fe III complexes with different coordination environments in which the Fe III atoms are coordinated by a different number of thio-cyanate anions and 4-meth-oxy-pyridine ligands. Charge balance is achieved by 4-meth-oxy-pyridinium cations. The asymmetric unit consists of three Fe III cations, one of which is located on a centre of inversion, one on a twofold rotation axis and one in a general position, and ten thio-cyanate anions, two 4-meth-oxy-pyridine ligands and 4-meth-oxy-pyridinium cations (one of which is disordered over two sets of sites). Beside to Coulombic inter-actions between organic cations and the ferrate(III) anions, weak N-H⋯S hydrogen-bonding inter-actions involving the pyridinium N-H groups of the cations and the thio-cyanate S atoms of the complex anions are mainly responsible for the cohesion of the crystal structure.

Crystal structure of trans-bis­(ethane-1,2-diamine-κ2 N,N′)bis­(thio­cyanato-κN)chromium(III) perchlorate from synchrotron data

PubMed Central

Moon, Dohyun; Choi, Jong-Ha

2015-01-01

The structure of the title compound, [Cr(NCS)2(C2H8N2)2]ClO4, has been determined from synchroton data. The asymmetric unit consists of one half of a centrosymmetric CrIII complex cation and half of a perchlorate anion with the Cl atom on a twofold rotation axis. The CrIII ion is coordinated by the four N atoms of two ethane-1,2-di­amine (en) ligands in the equatorial plane and two N-bound thio­cyanate (NCS−) anions in a trans-axial arrangement, displaying a slightly distorted octa­hedral geometry with crystallographic inversion symmetry. The Cr—N(en) bond lengths are in the range 2.053 (16)–2.09 (2) Å, while the Cr—N(thio­cyanate) bond length is 1.983 (2) Å. The five-membered en rings are disordered over two sites, with occupancy ratios of 0.522 (16):0.478 (16). Each ClO4 − anion is disordered over two sites with equal occupancy. The crystal structure is stabilized by inter­molecular hydrogen bonds involving the en NH2 groups as donors and perchlorate O and thio­cyanate S atoms as acceptors. PMID:26090142

Triptycene-Based Microporous Cyanate Resins for Adsorption/Separations of Benzene/Cyclohexane and Carbon Dioxide Gas.

PubMed

Deng, Gaoyang; Wang, Zhonggang

2017-11-29

Triptycene-based cyanate monomers 2,6,14-tricyanatotriptycene (TPC) and 2,6,14-tris(4-cyanatophenyl)triptycene (TPPC) that contain different numbers of benzene rings per molecule were synthesized, from which two microporous cyanate resins PCN-TPC and PCN-TPPC were prepared. Of interest is the observation that the two polymers have very similar porosity parameters, but PCN-TPPC uptakes considerably higher benzene (77.8 wt %) than PCN-TPC (17.6 wt %) at room temperature since the higher concentration of phenyl groups in PCN-TPPC enhances the π-π interaction with benzene molecules. Besides, the adsorption capacity of benzene in PCN-TPPC is dramatically 7 times as high as that of cyclohexane. Contrary to the adsorption of organic vapors, at 273 K and 1.0 bar, PCN-TPC with more heteroatoms in the network skeleton displays larger uptake of CO 2 and higher CO 2 /N 2 selectivity (16.4 wt %, 60) than those of PCN-TPPC (14.0 wt %, 39). The excellent and unique adsorption properties exhibit potential applications in the purification of small molecular organic hydrocarbons, e.g., separation of benzene from benzene/cyclohexane mixture as well as CO 2 capture from flue gas. Moreover, the results are helpful for deeply understanding the effect of porous and chemical structures on the adsorption properties of organic hydrocarbons and CO 2 gas.

Target-oriented discovery of a new esterase-producing strain Enterobacter sp. ECU1107 for whole cell-catalyzed production of (2S,3R)-3-phenylglycidate as a chiral synthon of Taxol.

PubMed

Zhou, Dong-Jie; Pan, Jiang; Yu, Hui-Lei; Zheng, Gao-Wei; Xu, Jian-He

2013-07-01

A new strain, Enterobacter sp. ECU1107, was identified among over 200 soil isolates using a two-step screening strategy for the enantioselective synthesis of (2S,3R)-3-phenylglycidate methyl ester (PGM), a key intermediate for production of a potent anticancer drug Taxol®. An organic-aqueous biphasic system was employed to reduce spontaneous hydrolysis of the substrate PGM and isooctane was found to be the most suitable organic solvent. The temperature and pH optima of the whole cell-mediated bioreaction were 40 °C and 6.0, respectively. Under these reaction conditions, the enantiomeric excess (ee(s)) of (2S,3R)-PGM recovered was greater than 99 % at approximately 50 % conversion. The total substrate loading in batch reaction could reach 600 mM. By using whole cells of Enterobacter sp. ECU1107, (2S,3R)-PGM was successfully prepared in decagram scale in a 1.0-l mechanically stirred reactor, affording the chiral epoxy ester in >99 % ee s and 43.5 % molar yield based on the initial load of racemic substrate.

Novel self-healing materials chemistries for targeted applications

NASA Astrophysics Data System (ADS)

Wilson, Gerald O.

Self-healing materials of the type developed by White and co-workers [1] were designed to autonomically heal themselves when damaged, thereby extending the lifetime of various applications in which such material systems are employed. The system was based on urea-formaldehyde microcapsules containing dicyclopentadiene (DCPD) and Grubbs' catalyst particles embedded together in an epoxy matrix. When a crack propagates through the material, it ruptures the microcapsules, releasing DCPD into the crack plane, where it comes in contact and reacts with the catalyst to initiate a ring opening metathesis polymerization (ROMP), bonding the crack and restoring structural continuity. The present work builds on this concept in several ways. Firstly, it expands the scope and versatility of the ROMP self-healing chemistry by incorporation into epoxy vinyl ester matrices. Major technical challenges in this application include protection of the catalyst from deactivation by aggressive curing agents, and optimization of the concentration of healing agents in the matrix. Secondly, new ruthenium catalysts are evaluated for application in ROMP-based self-healing materials. The use of alternative derivatives of Grubbs' catalyst gave rise to self-healing systems with improved healing efficiencies and thermal properties. Evaluation of the stability of these new catalysts to primary amine curing agents used in the curing of common epoxy matrices also led to the discovery and characterization of new ruthenium catalysts which exhibited ROMP initiation kinetics superior to those of first and second generation Grubbs' catalysts. Finally, free radical polymerization was evaluated for application in the development of bio-compatible self-healing materials. [1] White, S. R.; Sottos, N. R.; Geubelle, P. R.; Moore, J. S.; Kessler, M. R.; Sriram, S. R.; Brown, E. N.; Viswanathan, S. Nature 2001, 409, 794.

Tris{2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate-κ2 O,O′}tris­(thio­cyanato-κN)europium(III)

PubMed Central

Liu, Jian-Feng; Liu, Jia-Lu; Zhao, Guo-Liang

2009-01-01

The metal center in the structure of the title compound, [Eu(NCS)3(C15H15NO2)3], is coordinated by three Schiff base 2-meth­oxy-6-[(4-methyl­phen­yl)iminiometh­yl]phenolate (L) ligands and three independent thio­cyanate ions. In the crystal structure, the acidic H atom is located on the Schiff base N atom and hydrogen bonded to the phenolate O atom. The coordination environment of the EuIII ion is nine-coordinate by three chelating methoxy­phenolate pairs of O atoms and three N-atom terminals of the thio­cyanate ions. The compound is isostructural with the CeIII analogue [Liu et al. (2009 ▶). Acta Cryst. E65, m650]. PMID:21578663

Crystal structure of octa­kis­(4-meth­oxy­pyridinium) bis­(4-meth­oxy­pyridine-κN)tetra­kis­(thio­cyanato-κN)ferrate(III) bis­[(4-meth­oxypyri­dine-κN)pentakis­(thio­cyanato-κN)ferrate(III)] hexa­kis­(thio­cyanato-κN)ferrate(III) with iron in three different octa­hedral coordination environments

PubMed Central

Jochim, Aleksej; Jess, Inke; Näther, Christian

2018-01-01

The crystal structure of the title salt, (C6H8NO)8[Fe(NCS)4(C6H7NO)2][Fe(NCS)5(C6H7NO)]2[Fe(NCS)6], comprises three negatively charged octa­hedral FeIII complexes with different coordination environments in which the FeIII atoms are coordinated by a different number of thio­cyanate anions and 4-meth­oxy­pyridine ligands. Charge balance is achieved by 4-meth­oxy­pyridinium cations. The asymmetric unit consists of three FeIII cations, one of which is located on a centre of inversion, one on a twofold rotation axis and one in a general position, and ten thio­cyanate anions, two 4-meth­oxy­pyridine ligands and 4-meth­oxy­pyridinium cations (one of which is disordered over two sets of sites). Beside to Coulombic inter­actions between organic cations and the ferrate(III) anions, weak N—H⋯S hydrogen-bonding inter­actions involving the pyridinium N—H groups of the cations and the thio­cyanate S atoms of the complex anions are mainly responsible for the cohesion of the crystal structure. PMID:29765708

Swimming Pools, Hot Rods, and Qualitative Analysis.

ERIC Educational Resources Information Center

Clyde, Dale D.

1988-01-01

Describes some reactions for the identification and application of cyanuric acid. Suggests students may find this applied chemistry interesting because of the use of cyanuric acid in swimming pools and diesel engines. Lists three tests for cyanate ion and two tests for cyanuric acid. (MVL)

Microbial Thiocyanate Utilization under Highly Alkaline Conditions

PubMed Central

Sorokin, Dimitry Y.; Tourova, Tatyana P.; Lysenko, Anatoly M.; Kuenen, J. Gijs

2001-01-01

Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS−) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO−) to ammonia and CO2. On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a “cyanate pathway” in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate. PMID:11157213

Liebig-Wohler Controversy and the Concept of Isomerism

ERIC Educational Resources Information Center

Esteban, Soledad

2008-01-01

Very often controversies contribute to the development of science. An example is the conflict between Liebig and Wohler on the occasion of their analyses of fulminates and cyanates, which showed that compounds with different properties could have the same composition. Their results, together with other similar evidences, led Berzelius to recognize…

Magnetic graphitic carbon nitride: its application in the C–H activation of amines

EPA Science Inventory

Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for expeditious C-H activation and cyanation of ...

Catalytic asymmetric epoxidation of alpha,beta-unsaturated amides: efficient synthesis of beta-aryl alpha-hydroxy amides using a one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process.

PubMed

Nemoto, Tetsuhiro; Kakei, Hiroyuki; Gnanadesikan, Vijay; Tosaki, Shin-Ya; Ohshima, Takashi; Shibasaki, Masakatsu

2002-12-11

The catalytic asymmetric epoxidation of alpha,beta-unsaturated amides using Sm-BINOL-Ph3As=O complex was succeeded. Using 5-10 mol % of the asymmetric catalyst, a variety of amides were epoxidized efficiently, yielding the corresponding alpha,beta-epoxy amides in up to 99% yield and in more than 99% ee. Moreover, the novel one-pot tandem process, one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process, was developed. This method was successfully utilized for the efficient synthesis of beta-aryl alpha-hydroxy amides, including beta-aryllactyl-leucine methyl esters. Interestingly, it was found that beneficial modifications on the Pd catalyst were achieved by the constituents of the first epoxidation, producing a more suitable catalyst for the Pd-catalyzed epoxide opening reaction in terms of chemoselectivity.

HPLC method for determination of biologically active epoxy-transformers of treosulfan in human plasma: pharmacokinetic application.

PubMed

Główka, Franciszek K; Romański, Michał; Teżyk, Artur; Zaba, Czesław; Wróbel, Tomasz

2012-03-25

Clinical trials demonstrated treosulfan (TREO) as a promising myeloablative agent prior to hematopoietic stem cell transplantation (HSCT). TREO is a specific pro-drug from which biologically active mono- (S,S-EBDM) and diepoxybutane (S,S-DEB) derivatives are formed in vitro or in vivo by a non-enzymatic pH and temperature-dependent intramolecular nucleophilic substitution. Following extraction of the plasma samples with a mixture of dichloromethane and acetonitrile, S,S-EBDM and S,S-DEB were derivatized with 3-nitrobenzenesulfonic acid (3-NBS) to UV-absorbing esters. Optimal temperature and time of derivatization as well as extraction method and also the effect of pH on TREO stability in plasma were established. Identity of the synthesized derivatives was confirmed by mass spectrometry. The post-derivatization mixture was purified from the excess of unreacted 3-NBS by extraction with water. The derivatization products and 2,2'-dinitrobiphenyl (internal standard) were separated on Nucleosil 100 C18 column using a mobile phase consisted of acetonitrile and water. The developed method was validated and demonstrated adequate accuracy and precision. Limit of quantification for both S,S-EBDM and S,S-DEB amounted to 2.5 μM. The method was applied in clinical conditions to quantify the levels of TREO activation products in plasma of children undergoing HSCT. The methodology for simultaneous determination of TREO epoxy-transformers in human plasma is described for the first time. Copyright © 2011 Elsevier B.V. All rights reserved.

Study of the time varying properties of flax fiber reinforced composites

NASA Astrophysics Data System (ADS)

Stochioiu, Constantin; Chettah, Ameur; Piezel, Benoit; Fontaine, Stéphane; Gheorghiu, Horia-Miron

2018-02-01

Bio materials have seen an increase of interest from the scientific community and the industry as a possible future generation of mass produced materials, some of the main arguments being their renewability, low production costs and recyclability. The current work is focused on the experimental data required for the viscoelastic characterization of a composite material. Similar work has been conducted on different types of composite materials by Tuttle and Brinson [1] who verified for a carbon epoxy laminate the possibility of long term predicament of creep. Nordin et al [2] studied paper impregnated with phenol-formaldehyde under compression. Muliana [3] conducted experiments on E-glass/vinyl ester materials. Behavior characterization was based on a model presented by Schapery [4]. The main objective of this work is to understand the mechanical behaviors of bio-laminates structures subjected to long and severe operating conditions. The studied material is a bio composite laminate consisting in long flax fibers embedded in an epoxy resin system. The laminates were obtained from pre-impregnated unidirectional fibers, which were cured though a thermo-compression cycle followed by a post curing cycle. Test specimens were cut down to sizes, with the help of an electric saw. The concerned fiber direction was 0° with sample dimensions of 250x25x2 mm. First, testing consisted in quasi static mechanical tests. Second, to characterize linear viscoelastic behavior of the bio-laminates, creep - recovery tests with multiple load levels have been performed for the chosen fiber direction.

Design guidelines for high dimensional stability of CFRP optical bench

NASA Astrophysics Data System (ADS)

Desnoyers, Nichola; Boucher, Marc-André; Goyette, Philippe

2013-09-01

In carbon fiber reinforced plastic (CFRP) optomechanical structures, particularly when embodying reflective optics, angular stability is critical. Angular stability or warping stability is greatly affected by moisture absorption and thermal gradients. Unfortunately, it is impossible to achieve the perfect laminate and there will always be manufacturing errors in trying to reach a quasi-iso laminate. Some errors, such as those related to the angular position of each ply and the facesheet parallelism (for a bench) can be easily monitored in order to control the stability more adequately. This paper presents warping experiments and finite-element analyses (FEA) obtained from typical optomechanical sandwich structures. Experiments were done using a thermal vacuum chamber to cycle the structures from -40°C to 50°C. Moisture desorption tests were also performed for a number of specific configurations. The selected composite material for the study is the unidirectional prepreg from Tencate M55J/TC410. M55J is a high modulus fiber and TC410 is a new-generation cyanate ester designed for dimensionally stable optical benches. In the studied cases, the main contributors were found to be: the ply angular errors, laminate in-plane parallelism (between 0° ply direction of both facesheets), fiber volume fraction tolerance and joints. Final results show that some tested configurations demonstrated good warping stability. FEA and measurements are in good agreement despite the fact that some defects or fabrication errors remain unpredictable. Design guidelines to maximize the warping stability by taking into account the main dimensional stability contributors, the bench geometry and the optical mount interface are then proposed.

Sildenafil Stimulates the Expression of Gaseous Monoxide-Generating Enzymes in Vascular Smooth Muscle Cells via Distinct Signaling Pathways

PubMed Central

Liu, Xiao-ming; Peyton, Kelly J.; Wang, Xinhui; Durante, William

2012-01-01

Sildenafil is a cGMP-specific phosphodiesterase type 5 inhibitor that augments cGMP accumulation following the activation of soluble guanylate cyclase (sGC). In this study, we investigated whether sildenafil promotes the production of the sGC-stimulatory gases, carbon monoxide and nitric oxide, by stimulating the expression of the inducible isoforms of heme oxygenase (HO-1) and nitric oxide synthase (iNOS) in vascular smooth muscle cells (SMCs). Sildenafil increased HO-1 expression and potentiated cytokine-mediated expression of iNOS and NO synthesis by SMCs. The induction of HO-1 was unaffected by the sGC inhibitor 1H-(1,2,4)oxadiazolo[4,3-α]quinozalin-1-one (ODQ) or the (9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindol91,2,3-fg:3′,2′,1′-kl)pyrrolo(3,4-i)benzodiazocine-10-carboxylic acid, methyl ester (KT 5823). However, the sildenafil-mediated increase in HO-1 promoter activity was abolished by mutating the antioxidant responsive elements in the promoter or by overexpressing a dominant-negative mutant of NF-E2-related factor-2 (Nrf2). Furthermore, the induction of HO-1 by sildenafil was accompanied by an increase in reactive oxygen species (ROS) and blocked by N-acetyl-L-cysteine and rotenone. In contrast, the enhancement of cytokine-stimulated NO synthesis by sildenafil was prevented by ODQ and the protein kinase A inhibitor (9S,10S,12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo(1,2,3-fg:3′,2′,1′-kl)pyrrolo(3,4-i)(1,6)benzodiazocine-10-carboxylic acid hexyl ester (KT 5720) and duplicated by lipophilic analogues of cGMP. In conclusion, these studies demonstrate that sildenafil stimulates the expression of HO-1 and iNOS via the ROS-Nrf2 and sGC-cGMP pathway, respectively. The ability of sildenafil to block the catabolism of cGMP while stimulating the synthesis of sGC-stimulatory gaseous monoxides through the induction of HO-1 and iNOS provides a potent mechanism by which cGMP-dependent vascular actions of this drug are amplified. PMID:22864061

Cross-reactivity among epoxy acrylates and bisphenol F epoxy resins in patients with bisphenol A epoxy resin sensitivity.

PubMed

Lee, Han N; Pokorny, Christopher D; Law, Sandra; Pratt, Melanie; Sasseville, Denis; Storrs, Frances J

2002-09-01

The study's objective was 2-fold: first, to evaluate the potential cross-reactivity between Bis-A epoxy resins and epoxy acrylates and second, to study the cross reactivity between Bis-A epoxy resins and newer Bis-F epoxy resins in patients with allergic contact dermatitis to epoxy resins and had positive patch test to the standard epoxy resin based on bisphenol A. Forty-one patients were patch tested to 23 chemicals including epoxy acrylates, Bis-A epoxy resins, and Bis-F epoxy resins, as well as reactive diluents and nonbisphenol epoxy resins. Questions concerning exposure to epoxy resins, occupational history, and problems with dental work were completed. All patients included in the study had positive reactions to the standard Bis-A epoxy resin. Twenty percent (8 of 41) of the patients reacted to at least one of the epoxy acrylates; the most common reaction was to Bis-GMA. Five of 8 patients who reacted to the epoxy acrylates had dental work, but only one patient had problems from her dental work. Six of 8 patients (75%) who reacted to epoxy resins and epoxy acrylates did not react to aliphatic acrylates. Thirty-two percent (13 of 41) reacted to tosylamide epoxy resin, and none reacted to triglycidyl isocyanurate resin. In addition, all patients (100%) had positive reactions to at least one of the Bis-F epoxy resins that were tested. Most patients with sensitivity to Bis-A epoxy resins do not cross-react with epoxy acrylates. Patients with positive patch test reactions to epoxy acrylates used in dentistry usually do not have symptoms from their dental work. To our knowledge, this is the largest series of patients with sensitivity to the standard Bis-A epoxy resin that have been patch tested with the more recently introduced Bis-F epoxy resins. There is significant cross-reactivity between Bis-A and Bis-F epoxy resins, which can be explained by their structural similarity. Copyright 2002, Elsevier Science (USA). All rights reserved.

Mechanism and scope of the cyanide-catalyzed cross silyl benzoin reaction.

PubMed

Linghu, Xin; Bausch, Cory C; Johnson, Jeffrey S

2005-02-16

In this work, cross silyl benzoin addition reactions between acylsilanes (1) and aldehydes (2) catalyzed by metal cyanides are described. Unsymmetrical aryl-, heteroaryl-, and alkyl-substituted benzoin adducts can be generated in moderate to excellent yields with complete regiocontrol using potassium cyanide and a phase transfer catalyst. From a screen of transition metal cyanide complexes, lanthanum tricyanide was identified as an improved second-generation catalyst for the cross silyl benzoin reaction. A study of the influence of water on the KCN-catalyzed cross silyl benzoin addition revealed more practical reaction conditions using unpurified solvent under ambient conditions. A sequential silyl benzoin addition/cyanation/O-acylation reaction that resulted in two new C-C bonds was achieved in excellent yield. The mechanism of cross silyl benzoin addition is proposed in detail and is supported by crossover studies and a number of unambiguous experiments designed to ascertain the reversibility of key steps. No productive chemistry arises from cyanation of the more electrophilic aldehyde component. Formation of the carbon-carbon bond is shown to be the last irreversible step in the reaction.

The binding of carbon dioxide by horse haemoglobin

PubMed Central

Kilmartin, J. V.; Rossi-Bernardi, L.

1971-01-01

1. Three modified horse haemoglobins have been prepared: (i) αc2βc2, in which both the α-amino groups of the α- and β-chains have reacted with cyanate, (ii) αc2β2, in which the α-amino groups of the α-chains have reacted with cyanate, and (iii) α2βc2, in which the two α-amino groups of the β-chain have reacted with cyanate. 2. The values of n (the Hill constant) for αc2βc2, α2βc2 and αc2β2 were (respectively) 2.5, 2.0 and 2.6, indicating the presence of co-operative interactions between the haem groups for all derivatives. 3. In the alkaline pH range (about pH8.0) all the derivatives show the same charge as normal haemoglobin whereas in the acid pH range (about pH6.0) αc2βc2 differs by four protonic charges and αc2β2, α2βc2 by two protonic charges from normal haemoglobin, indicating that the expected number of ionizing groups have been removed. 4. αc2β2 and αc2βc2 show a 25% decrease in the alkaline Bohr effect, in contrast with α2βc2, which has the same Bohr effect as normal haemoglobin. 5. The deoxy form of αc2βc2 does not bind more CO2 than the oxy form of αc2βc2, whereas αc2β2 and α2βc2 show intermediate binding. 6. The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO2 through the four terminal α-amino groups and that the two terminal α-amino groups of α-chains are involved in the Bohr effect. ImagesPLATE 1 PMID:5166592

Analytical method for the trace determination of esterified 3- and 2-monochloropropanediol and glycidyl fatty acid esters in various food matrices.

PubMed

Samaras, Vasilios G; Giri, Anupam; Zelinkova, Zuzana; Karasek, Lubomir; Buttinger, Gerhard; Wenzl, Thomas

2016-09-30

Fatty acid esters of 3-monochloro-1,2-propanediol (3-MCPDEs), of 2-monochloro-1,3-propanediol (2-MCPDEs) and of 2,3-epoxy-1-propanol or glycidol (GEs), which are considered to be deleterious to human health, may occur in a broad variety of food samples. A proper risk assessment of those substances requires the availability of robust occurrence data; in this respect concerns have been raised regarding the reliability of results obtained with the currently available methods to determine those substances in processed food. This article presents an indirect analytical procedure for the simultaneous determination of 3-MCPDEs, 2-MCPDEs and GEs in a wide variety of food products after extraction by pressurised liquid extraction (PLE) and determination by gas chromatography mass-spectrometry (GC-MS). For the differentiation of MCPDEs and GEs, the latter were first converted to monobromopropanediol esters (MBPDEs) in acid aqueous solution of sodium bromide. MCPDEs and MBPDEs were then hydrolysed under acidic conditions followed by derivatisation of the released free (non-esterified) form in ethyl acetate with phenyl boronic acid (PBA). Quantification of the analytes was carried out using the isotopic labelled analogues of both MCPDEs and GEs. Limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 7-17mgkg(-1) and 13-31mgkg(-1) respectively, while the working range of the method was between LOQ and 1850mgkg(-1) expressed on fat basis. The developed method was successfully applied for the analysis of the target compounds in more than 650 different food samples covering the following commodities: bread and rolls, fine bakery wares, smoked fish products, fried and roasted meat, potato based snacks and fried potato products, cereal-based snacks and margarines. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Characterization of epoxy carotenoids by fast atom bombardment collision-induced dissociation MS/MS.

PubMed

Maoka, Takashi; Fujiwara, Yasuhiro; Hashimoto, Keiji; Akimoto, Naoshige

2004-02-01

The characterization and structure of epoxy carotenoids possessing 5,6-epoxy, 5,8-epoxy and 3,6-epoxy end groups conjugated to the polyene chain were investigated using high-energy fast atom bombardment collision-induced dissociation MS/MS methods. In addition to [M - 80](+*), a characteristic fragment ion of an epoxy carotenoid, product ions resulting from the cleavage of C-C bonds in the polyene chain from the epoxy end group, such as m/z 181 (b ion) and 121 (c ion), were detected. On the other hand, diagnostic ions of m/z 286 (e-H ion) and 312 (f-H ion) were observed, not in the 5,6-epoxy or 5,8-epoxy carotenoid but in the 3,6-epoxy carotenoid. These fragmentation patterns can be used to distinguish 3,6-epoxy carotenoids from 5,6-epoxy or 5,8-epoxy carotenoids. The structure of an epoxy carotenoid, 3,6-epoxy-5,6-dihydro-7',8'-didehydro-beta,beta-carotene-5,3'-diol (8), isolated from oyster, was characterized using FAB CID-MS/MS by comparing fragmentation patterns with those of related known compounds.

Formation of Plant Sterol Oxidation Products in Foods during Baking and Cooking Using Margarine without and with Added Plant Sterol Esters.

PubMed

Lin, Yuguang; Knol, Diny; Menéndez-Carreño, María; Blom, Wendy A M; Matthee, Joep; Janssen, Hans-Gerd; Trautwein, Elke A

2016-01-27

Plant sterols (PS) in foods are subject to thermal oxidation to form PS oxidation products (POP). This study measured POP contents of 19 foods prepared by typical household baking and cooking methods using margarines without (control) and with 7.5% added PS (as 12.5% PS-esters, PS-margarine). Median POP contents per portion size of cooked foods were 0.57 mg (range 0.05-1.11 mg) with control margarine versus 1.42 mg (range 0.08-20.5 mg) with PS-margarine. The oxidation rate of PS (ORP) was 0.50% (median) with the PS-margarine and 3.66% with the control margarine. Using the PS-margarine, microwave-cooked codfish had the lowest POP content, with 0.08 mg per portion, while shallow-fried potatoes had the highest POP content, 20.5 mg per portion. Median POP contents in cookies, muffins, banana bread, and sponge cake baked with the control or PS-margarine were 0.12 mg (range 0.11-0.21 mg) and 0.24 mg (range 0.19-0.60 mg) per portion, with a corresponding ORP of 1.38% and 0.06%, respectively. POP contents in all the cooked and baked foods did not exceed 20.5 mg per typical portion size. A wide variation in the distribution of individual POP among different foods existed, with 7-keto-PS and 5,6-epoxy-PS being the major oxidation products.

Effects of Nanofillers on the Thermo-Mechanical Properties and Chemical Resistivity of Epoxy Nanocomposites.

PubMed

Atchudan, Raji; Pandurangan, Arumugam; Joo, Jin

2015-06-01

MWCNTs was synthesized using Ni-Cr/MgO by CVD method and were purified. The purified MWCNT was used as a filler material for the fabrication of epoxy nanocomposites. The epoxy nanocomposites with different amount (wt% = 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0) of nanofillers (CB, SiO2 and MWCNTs) were prepared by casting method. The effects of nanofillers on the properties of neat epoxy matrix were well studied. The thermal properties of nanocomposites were studied using DSC, TGA and flame retardant, and also the mechanical properties such as tensile strength, flexural strength, compressive strength, impact strength, determination of hardness and chemical resistance were studied extensively. Based on the experiment's results, 2 wt% MWCNTs loading in epoxy resin showed the highest improvement in tensile strength, as compared to neat epoxy and to other epoxy systems (CB/epoxy, SiO2/epoxy). Improvements in tensile strength, glass transition temperature and decomposition temperature were observed by the addition of MWCNTs. The mechanical properties of the epoxy nanocomposites were improved due to the interfacial bonding between the MWCNTs and epoxy resin. Strain hardening behavior was higher for MWCNT/epoxy nanocomposites compared with CB/epoxy and SiO2/epoxy nanocomposites. The investigation of thermal and mechanical properties reveals that the incorporation of MWCNTs into the epoxy nanocomposites increases its thermal stability to a great extent. Discrete increase of glass transition temperature of nanocomposites is linearly dependent on MWCNTs content. Due to strong interfacial bonding between MWCNTs and epoxy resin, the chemical resistivity of MWCNT/epoxy nanocomposites is superior to neat epoxy and other epoxy systems.

Sodium cyanate-induced opening of calcium-activated potassium currents in hippocampal neuron-derived H19-7 cells.

PubMed

Huang, Chin-Wei; Huang, Chao-Ching; Huang, Mei-Han; Wu, Sheng-Nan; Hsieh, Yi-Jung

2005-03-29

We investigated the chemical toxic agent sodium cyanate (NaOCN) on the large conductance calcium-activated potassium channels (BK(Ca)) on hippocampal neuron-derived H19-7 cells. The whole-cell and cell-attach configuration of patch-clamp technique were applied to investigate the BK(Ca) currents in H19-7 cells in the presence of NaOCN (0.3 mM). NaOCN activated BK(Ca) channels on H19-7 cells. The single-channel conductance of BK(Ca) channels was 138+/-7pS. The presence of NaOCN (0.3 mM) caused an obvious increase in open probability of BK(Ca) channels. NaOCN did not exert effect on the slope of the activation curve and stimulated the activity of BK(Ca) channels in a voltage-dependent fashion in H19-7 cells. The presence of paxilline or EGTA significantly reduced the BK(Ca) amplitude, in comparison with the presence of NaOCN. These findings suggest that during NaOCN exposure, the activation of BK(Ca) channels in neurons could be one of the ionic mechanisms underlying the decreased neuronal excitability and neurological disorders.

The application of epoxy resin coating in grounding grid

NASA Astrophysics Data System (ADS)

Hu, Q.; Chen, Z. R.; Xi, L. J.; Wang, X. Y.; Wang, H. F.

2018-01-01

Epoxy resin anticorrosion coating is widely used in grounding grid corrosion protection because of its wide range of materials, good antiseptic effect and convenient processing. Based on the latest research progress, four kinds of epoxy anticorrosive coatings are introduced, which are structural modified epoxy coating, inorganic modified epoxy coating, organic modified epoxy coating and polyaniline / epoxy resin composite coating. In this paper, the current research progress of epoxy base coating is analyzed, and prospected the possible development direction of the anti-corrosion coating in the grounding grid, which provides a reference for coating corrosion prevention of grounding materials.

Process for Preparing Epoxy-Reinforced Silica Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B (Inventor)

2016-01-01

One-pot reaction process for preparing epoxy-reinforced monolithic silica aerogels comprising the reaction of at least one silicon compound selected from the group consisting of alkoxysilanes, orthosilicates and combination thereof in any ratio with effective amounts of an epoxy monomer and an aminoalkoxy silane to obtain an epoxy monomer-silica sol in solution, subsequently preparing an epoxy-monomer silica gel from said silica sol solution followed by initiating polymerization of the epoxy monomer to obtain the epoxy-reinforced monolithic silica aerogel.

Synthesis of polyoxometalate-loaded epoxy composites

DOEpatents

Anderson, Benjamin J

2014-10-07

The synthesis of a polyoxometalate-loaded epoxy uses a one-step cure by applying an external stimulus to release the acid from the polyoxometalate and thereby catalyze the cure reaction of the epoxy resin. Such polyoxometalate-loaded epoxy composites afford the cured epoxy unique properties imparted by the intrinsic properties of the polyoxometalate. For example, polyoxometalate-loaded epoxy composites can be used as corrosion resistant epoxy coatings, for encapsulation of electronics with improved dielectric properties, and for structural applications with improved mechanical properties.

Determination of Young's modulus of epoxy coated polyethylene micro-cantilever using phase-shift shadow moiré method

NASA Astrophysics Data System (ADS)

Lim, J. H.; Ratnam, M. M.; Azid, I. A.; Mutharasu, D.

2011-11-01

Young's moduli of various epoxy coated polyethylene terephthalate (PET) micro-cantilevers were determined from the deflection results obtained using the phase-shift shadow moiré (PSSM) method. The filler materials for epoxy coatings were aluminum and graphite powders that were mixed with epoxy at various percentages. Young's moduli were calculated from theory based on the deflection results. The PET micro-cantilever coated with aluminum-epoxy coating showed increasing value of Young's modulus when the ratios of the aluminum-epoxy were increased. The graphite-epoxy coating on the PET micro-cantilever also showed the same trend. The experimental results also show that Young's modulus of the graphite-epoxy coating is higher than aluminum-epoxy coating in comparison at the same mixing ratio.

Evaluation of composite flattened tubular specimen. [fatigue tests

NASA Technical Reports Server (NTRS)

Liber, T.; Daniel, I. M.

1978-01-01

Flattened tubular specimens of graphite/epoxy, S-glass/epoxy, Kevlar-49/epoxy, and graphite/S-glass/epoxy hybrid materials were evaluated under static and cyclic uniaxial tensile loading and compared directly with flat coupon data of the same materials generated under corresponding loading conditions. Additional development for the refinement of the flattened specimen configuration and fabrication was required. Statically tested graphite/epoxy, S-glass/epoxy, and Kevlar 49/epoxy flattened tube specimens exhibit somewhat higher average strengths than their corresponding flat coupons. Flattened tube specimens of the graphite/S-glass/epoxy hybrid and the graphite/epoxy flattened tube specimens failed in parasitic modes with consequential lower strength than the corresponding flat coupons. Fatigue tested flattened tube specimens failed in parasitic modes resulting in lower fatigue strengths than the corresponding flat coupons.

Mechanical Properties and Morphologies of Carboxyl-Terminated Butadiene Acrylonitrile Liquid Rubber/Epoxy Blends Compatibilized by Pre-Crosslinking.

PubMed

Xu, Shiai; Song, Xiaoxue; Cai, Yangben

2016-07-29

In order to enhance the compatibilization and interfacial adhesion between epoxy and liquid carboxyl-terminated butadiene acrylonitrile (CTBN) rubber, an initiator was introduced into the mixture and heated to initiate the cross-linking reaction of CTBN. After the addition of curing agents, the CTBN/epoxy blends with a localized interpenetrating network structure were prepared. The mechanical properties and morphologies of pre-crosslinked and non-crosslinked CTBN/epoxy blends were investigated. The results show that the tensile strength, elongation at break and impact strength of pre-crosslinked CTBN/epoxy blends are significantly higher than those of non-crosslinked CTBN/epoxy blends, which is primarily due to the enhanced interfacial strength caused by the chemical bond between the two phases and the localized interpenetrating network structure. Both pre-crosslinked and non-crosslinked CTBN/epoxy blends show a bimodal distribution of micron- and nano-sized rubber particles. However, pre-crosslinked CTBN/epoxy blends have smaller micron-sized rubber particles and larger nano-sized rubber particles than non-crosslinked CTBN/epoxy blends. The dynamic mechanical analysis shows that the storage modulus of pre-crosslinked CTBN/epoxy blends is higher than that of non-crosslinked CTBN/epoxy blends. The glass transition temperature of the CTBN phase in pre-crosslinked CTBN/epoxy blends increases slightly compared with the CTBN/epoxy system. The pre-crosslinking of rubber is a promising method for compatibilization and controlling the morphology of rubber-modified epoxy materials.

Mechanical Properties and Morphologies of Carboxyl-Terminated Butadiene Acrylonitrile Liquid Rubber/Epoxy Blends Compatibilized by Pre-Crosslinking

PubMed Central

Xu, Shiai; Song, Xiaoxue; Cai, Yangben

2016-01-01

In order to enhance the compatibilization and interfacial adhesion between epoxy and liquid carboxyl-terminated butadiene acrylonitrile (CTBN) rubber, an initiator was introduced into the mixture and heated to initiate the cross-linking reaction of CTBN. After the addition of curing agents, the CTBN/epoxy blends with a localized interpenetrating network structure were prepared. The mechanical properties and morphologies of pre-crosslinked and non-crosslinked CTBN/epoxy blends were investigated. The results show that the tensile strength, elongation at break and impact strength of pre-crosslinked CTBN/epoxy blends are significantly higher than those of non-crosslinked CTBN/epoxy blends, which is primarily due to the enhanced interfacial strength caused by the chemical bond between the two phases and the localized interpenetrating network structure. Both pre-crosslinked and non-crosslinked CTBN/epoxy blends show a bimodal distribution of micron- and nano-sized rubber particles. However, pre-crosslinked CTBN/epoxy blends have smaller micron-sized rubber particles and larger nano-sized rubber particles than non-crosslinked CTBN/epoxy blends. The dynamic mechanical analysis shows that the storage modulus of pre-crosslinked CTBN/epoxy blends is higher than that of non-crosslinked CTBN/epoxy blends. The glass transition temperature of the CTBN phase in pre-crosslinked CTBN/epoxy blends increases slightly compared with the CTBN/epoxy system. The pre-crosslinking of rubber is a promising method for compatibilization and controlling the morphology of rubber-modified epoxy materials. PMID:28773762

Chromatographic assessment of two hybrid monoliths prepared via epoxy-amine ring-opening polymerization and methacrylate-based free radical polymerization using methacrylate epoxy cyclosiloxane as functional monomer.

PubMed

Wang, Hongwei; Ou, Junjie; Lin, Hui; Liu, Zhongshan; Huang, Guang; Dong, Jing; Zou, Hanfa

2014-11-07

Two kinds of hybrid monolithic columns were prepared by using methacrylate epoxy cyclosiloxane (epoxy-MA) as functional monomer, containing three epoxy moieties and one methacrylate group. One column was in situ fabricated by ring-opening polymerization of epoxy-MA and 1,10-diaminodecane (DAD) using a porogenic system consisting of isopropanol (IPA), H2O and ethanol at 65°C for 12h. The other was prepared by free radical polymerization of epoxy-MA and ethylene dimethacrylate (EDMA) using 1-propanol and 1,4-butanediol as the porogenic solvents at 60°C for 12h. Two hybrid monoliths were investigated on the morphology and chromatographic assessment. Although two kinds of monolithic columns were prepared with epoxy-MA, their morphologies looked rather different. It could be found that the epoxy-MA-DAD monolith possessed higher column efficiencies (25,000-34,000plates/m) for the separation of alkylbenzenes than the epoxy-MA-EDMA monolith (12,000-13,000plates/m) in reversed-phase nano-liquid chromatography (nano-LC). Depending on the remaining epoxy or methacrylate groups on the surface of two pristine monoliths, the epoxy-MA-EDMA monolith could be easily modified with 1-octadecylamine (ODA) via ring-opening reaction, while the epoxy-MA-DAD monolith could be modified with stearyl methacrylate (SMA) via free radical reaction. The chromatographic performance for the separation of alkylbenzenes on SMA-modified epoxy-MA-DAD monolith was remarkably improved (42,000-54,000 plates/m) when compared with that on pristine epoxy-MA-DAD monolith, while it was not obviously enhanced on ODA-modified epoxy-MA-EDMA monolith when compared with that on pristine epoxy-MA-EDMA monolith. The enhancement of the column efficiency of epoxy-MA-DAD monolith after modification might be ascribed to the decreased mass-transfer resistence. The two kinds of hybrid monoliths were also applied for separations of six phenols and seven basic compounds in nano-LC. Copyright © 2014 Elsevier B.V. All rights reserved.

Allergic contact dermatitis from a nonbisphenol A epoxy in a graphite fiber reinforced epoxy laminate.

PubMed

Mathias, C G

1987-09-01

An employee of the Composites Division of an aircraft engine manufacturing firm developed dermatitis associated with the handling of a graphite fiber reinforced epoxy laminate (epoxy prepreg). Patch test investigation demonstrated that the responsible causal agent was the nonbisphenol A epoxy binder, 4-glycidyloxy-N, N-diglycidylaniline. A patch test with bisphenol A epoxy from a standard patch test screening series was negative. Subsequent interviews with employees of the Composites Division suggested that a relative lack of awareness of the cutaneous hazards of fiber reinforced epoxy laminates, compared with liquid epoxy resin systems, may be an important risk factor for allergic sensitization to these composite materials.

Synthesis and Characterization of Tetranitraminocyclobutanes

DTIC Science & Technology

1994-09-01

potassium cyanate in aqueous HCl yields urea acetal, 5, a white crystalline solid, which is dehydratively ring closed to imidazolidinone 6 in mild acid...dimerization produces exclusively the cis-trans-cis tetramine isomer as shown. Hydrolysis of the acetate groups is carried out in refluxing ethanol...there is some hydrolysis of the final product. Because nitramine 1 is under consideration as a potential replacement for pentaerythritol tetranitrate

Examination of Treatment Methods for Cyanide Wastes.

DTIC Science & Technology

1979-05-15

industry,is alkaline chlorination. This process oxidizes cyanide to cyanate followed by complete decomposition yielding carbon dioxide and nitrogen or...decomposition yielding carbon dioxide and nitrogen, or ammonium salts depending on final treatment methods. The major oxidizing agents that have been...2H20 (X represents a cation.) 29 NADC-78198-60 This liberates carbon dioxide and nitrogen gas as end products. Possible acid hydrolysis has been

Analysis of the Genes Involved in Thiocyanate Oxidation during Growth in Continuous Culture of the Haloalkaliphilic Sulfur-Oxidizing Bacterium Thioalkalivibrio thiocyanoxidans ARh 2T Using Transcriptomics

PubMed Central

Balkema, Cherel; Sorokin, Dimitry Y.

2017-01-01

ABSTRACT Thiocyanate (N=C−S−) is a moderately toxic, inorganic sulfur compound. It occurs naturally as a by-product of the degradation of glucosinolate-containing plants and is produced industrially in a number of mining processes. Currently, two pathways for the primary degradation of thiocyanate in bacteria are recognized, the carbonyl sulfide pathway and the cyanate pathway, of which only the former has been fully characterized. Use of the cyanate pathway has been shown in only 10 strains of Thioalkalivibrio, a genus of obligately haloalkaliphilic sulfur-oxidizing Gammaproteobacteria found in soda lakes. So far, only the key enzyme in this reaction, thiocyanate dehydrogenase (TcDH), has been purified and studied. To gain a better understanding of the other genes involved in the cyanate pathway, we conducted a transcriptomics experiment comparing gene expression during the growth of Thioalkalivibrio thiocyanoxidans ARh 2T with thiosulfate with that during its growth with thiocyanate. Triplicate cultures were grown in continuous substrate-limited mode, followed by transcriptome sequencing (RNA-Seq) of the total mRNA. Differential expression analysis showed that a cluster of genes surrounding the gene for TcDH were strongly upregulated during growth with thiocyanate. This cluster includes genes for putative copper uptake systems (copCD, ABC-type transporters), a putative electron acceptor (fccAB), and a two-component regulatory system (histidine kinase and a σ54-responsive Fis family transcriptional regulator). Additionally, we observed the increased expression of RuBisCO and some carboxysome shell genes involved in inorganic carbon fixation, as well as of aprAB, genes involved in sulfite oxidation through the reverse sulfidogenesis pathway. IMPORTANCE Thiocyanate is a moderately toxic and chemically stable sulfur compound that is produced by both natural and industrial processes. Despite its significance as a pollutant, knowledge of the microbial degradation of thiocyanate is very limited. Therefore, investigation of thiocyanate oxidation in haloalkaliphiles such as the genus Thioalkalivibrio may lead to improved biotechnological applications in wastewater remediation. PMID:29285524

Strain rate effects on mechanical properties of fiber composites, part 3

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1976-01-01

An experimental investigation was conducted to determine the strain rate effects in fiber composites. Unidirectional composite specimens of boron/epoxy, graphite/epoxy, S-glass/epoxy and Kevlar/epoxy were tested to determine longitudinal, transverse and intralaminar (in-plane) shear properties. In the Longitudinal direction the Kevlar/epoxy shows a definite increase in both modulus and strength with strain rate. In the transverse direction, a general trend toward higher strength with strain rate is noticed. The intralaminar shear moduli and strengths of boron/epoxy and graphite/epoxy show a definite rise with strain rate.

Testing Tensile and Shear Epoxy Strength at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Alberts, S. J.; Doehne, C. J.; Johnson, W. L.

2017-01-01

This paper covers cryogenic, tensile testing and research completed on a number of epoxies used in cryogenic applications. Epoxies are used in many different applications; however, this research focused on the use of epoxy used to bond MLI standoffs to cryogenic storage tanks and the loads imparted to the tank through the MLI. To conduct testing, samples were made from bare stainless steel, aluminum and primed aluminum. Testing involved slowly cooling test samples with liquid nitrogen then applying gradually increasing tensile loads to the epoxy. The testing evaluated the strength and durability of epoxies at cryogenic temperatures and serves as a base for future testing. The results of the tests showed that some epoxies withstood the harsh conditions while others failed. The two epoxies yielding the best results were Masterbond EP29LPSP and Scotch Weld 2216. For all metal surfaces tested, both epoxies had zero failures for up to 11.81 kg of mass..

Testing Tensile and Shear Epoxy Strength at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Alberts, S. J.; Doehne, C. J.; Johnson, W. L.

2017-01-01

This paper covers cryogenic, tensile testing and research completed on a number of epoxies used in cryogenic applications. Epoxies are used in many different applications; however, this research focused on the use of epoxy used to bond MLI standoffs to cryogenic storage tanks and the loads imparted to the tank through the MLI. To conduct testing, samples were made from bare stainless steel, aluminum and primed aluminum. Testing involved slowly cooling test samples with liquid nitrogen then applying gradually increasing tensile loads to the epoxy. The testing evaluated the strength and durability of epoxies at cryogenic temperatures and serves as a base for future testing. The results of the tests showed that some epoxies withstood the harsh conditions while others failed. The two epoxies yielding the best results were Masterbond EP29LPSP and Scotch Weld 2216. For all metal surfaces tested, both epoxies had zero failures for up to 11.81 kg of mass.

Contact allergy to epoxy hardeners.

PubMed

Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta

2014-09-01

Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Atomistic modeling of thermomechanical properties of SWNT/Epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Fasanella, Nicholas; Sundararaghavan, Veera

2015-09-01

Molecular dynamics simulations are performed to compute thermomechanical properties of cured epoxy resins reinforced with pristine and covalently functionalized carbon nanotubes. A DGEBA-DDS epoxy network was built using the ‘dendrimer’ growth approach where 75% of available epoxy sites were cross-linked. The epoxy model is verified through comparisons to experiments, and simulations are performed on nanotube reinforced cross-linked epoxy matrix using the CVFF force field in LAMMPS. Full stiffness matrices and linear coefficient of thermal expansion vectors are obtained for the nanocomposite. Large increases in stiffness and large decreases in thermal expansion were seen along the direction of the nanotube for both nanocomposite systems when compared to neat epoxy. The direction transverse to nanotube saw a 40% increase in stiffness due to covalent functionalization over neat epoxy at 1 K whereas the pristine nanotube system only saw a 7% increase due to van der Waals effects. The functionalized SWNT/epoxy nanocomposite showed an additional 42% decrease in thermal expansion along the nanotube direction when compared to the pristine SWNT/epoxy nanocomposite. The stiffness matrices are rotated over every possible orientation to simulate the effects of an isotropic system of randomly oriented nanotubes in the epoxy. The randomly oriented covalently functionalized SWNT/Epoxy nanocomposites showed substantial improvements over the plain epoxy in terms of higher stiffness (200% increase) and lower thermal expansion (32% reduction). Through MD simulations, we develop means to build simulation cells, perform annealing to reach correct densities, compute thermomechanical properties and compare with experiments.

Development of an enantioselective synthetic route to neocarzinostatin chromophore and its use for multiple radioisotopic incorporation.

PubMed

Myers, Andrew G; Glatthar, Ralf; Hammond, Marlys; Harrington, Philip M; Kuo, Elaine Y; Liang, Jun; Schaus, Scott E; Wu, Yusheng; Xiang, Jia-Ning

2002-05-15

A convergent, enantioselective synthetic route to the natural product neocarzinostatin chromophore (1) is described. Synthesis of the chromophore aglycon (2) was targeted initially. Chemistry previously developed for the synthesis of a neocarzinostatin core model (4) failed in the requisite 1,3-transposition of an allylic silyl ether when applied toward the preparation of 2 with use of the more highly oxygenated substrates 27 and 54. An alternative synthetic plan was therefore developed, based upon a proposed reduction of the epoxy alcohol 58 to form the aglycon 2, a transformation that was achieved in a novel manner, using a combination of the reagents triphenylphosphine, iodine, and imidazole. The successful route to 1 and 2 began with the convergent coupling of the epoxydiyne 15, obtained in 9 steps (43% overall yield) from D-glyceraldehyde acetonide, and the cyclopentenone (+)-14, prepared in one step (75-85% yield) from the prostaglandin intermediate (+)-16, affording the alcohol 22 in 80% yield and with > or =20:1 diastereoselectivity. The alcohol 22 was then converted into the epoxy alcohol 58 in 17 steps with an average yield of 92% and an overall yield of 22%. Key features of this sequence include the diastereoselective Sharpless asymmetric epoxidation of allylic alcohol 81 (98% yield); intramolecular acetylide addition within the epoxy aldehyde 82, using Masamune's lithium diphenyltetramethyldisilazide base (85% yield); selective esterification of the diol 84 with the naphthoic acid 13 followed by selective cleavage of the chloroacetate protective group in situ to furnish the naphthoic acid ester 85 in 80% yield; and elimination of the tertiary hydroxyl group within intermediate 88 using the Martin sulfurane reagent (79% yield). Reductive transposition of the product epoxy alcohol (58) then formed neocarzinostatin chromophore aglycon (2, 71% yield). Studies directed toward the glycosylation of 2 focused initially on the preparation of the N-methylamino --> hydroxyl replacement analogue 3, an alpha-D-fucose derivative of neocarzinostatin chromophore, formed in 42% yield by a two-step Schmidt glycosylation-deprotection sequence. For the synthesis of 1, an extensive search for a suitable 2'-N-methylfucosamine glycosyl donor led to the discovery that the reaction of 2 with the trichloroacetimidate 108, containing a free N-methylamino group, formed the alpha-glycoside 114 selectively in the presence of boron trifluoride diethyl etherate. Subsequent deprotection of 114 under mildly acidic conditions then furnished the labile chromophore (1). The synthetic route was readily modified for the preparation of singly and doubly (3)H- and (14)C-labeled 1, compounds unavailable by other means, for studies of the mechanism of action of neocarzinostatin in vivo.

Assessment of cross-reactivity of new less sensitizing epoxy resin monomers in epoxy resin-allergic individuals.

PubMed

Hagvall, Lina; Niklasson, Ida B; Rudbäck, Johanna; O'Boyle, Niamh M; Niklasson, Eva; Luthman, Kristina; Karlberg, Ann-Therese

2016-09-01

Measures to prevent occupational exposure to epoxy resins, including education, medical examination, and voluntary agreements between employers and workers, have not been effective enough to protect against skin sensitization. Therefore, alternatives to the major epoxy resin haptens that have been found to be less sensitizing in the local lymph node assay have been developed. To study the cross-reactivity of two newly designed epoxy resin monomers, with decreased skin-sensitizing potency and good technical properties as compared with diglycidyl ether of bisphenol A (DGEBA), in subjects with known contact allergy to epoxy resin of DGEBA type. Eleven individuals with previous positive patch test reactions to epoxy resin of DGEBA participated in the study. The two alternative epoxy resin monomers were synthesized and patch tested in dilution series in parallel with epoxy resin of DGEBA from the baseline series (containing 92% DGEBA). All participants reacted to epoxy resin of DGEBA on retesting. Three participants reacted to monomer 1. No reactions were seen to monomer 2. The alternative monomers studied showed little or no cross-reactivity with epoxy resin of DGEBA. Decreasing the risk of sensitization by using less sensitizing compounds is important, as contact allergy to epoxy resins is common in spite of thorough preventive measures. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of mechanical and thermal cycling on composite and hybrid laminates with residual stresses

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1977-01-01

The effects of tensile load cycling and thermal cycling on residual stiffness and strength properties of the following composite and hybrid angle-ply laminates were studied: boron/epoxy, boron/polyimide, graphite/low-modulus epoxy, graphite/high-modulus epoxy, graphite/polyimide, S-glass/epoxy, graphite/Kevlar 49/epoxy, and graphite/S-glass/epoxy. Specimens of the first six types were mechanically cycled up to 90% of static strength. Those that survived 10 million cycles were tested statically to failure, and no significant changes in residual strength and modulus were noted. Specimens of all types were subjected to thermal cycling between room temperature and 411 K for the epoxy-matrix composites and 533 K for the polyimide-matrix composites. The residual strength and stiffness remained largely unchanged, except for the graphite/low-modulus epoxy, which showed reductions in both of approximately 35%. When low-temperature thermal cycling under tensile load was applied, there was a noticeable reduction in modulus and strength in the graphite/low-modulus epoxy and some strength reduction in the S-glass/epoxy.

Moisture effect on interfacial integrity of epoxy-bonded system: a hierarchical approach

NASA Astrophysics Data System (ADS)

Tam, Lik-ho; Lun Chow, Cheuk; Lau, Denvid

2018-01-01

The epoxy-bonded system has been widely used in various applications across different scale lengths. Prior investigations have indicated that the moisture-affected interfacial debonding is the major failure mode of such a system, but the fundamental mechanism remains unknown, such as the basis for the invasion of water molecules in the cross-linked epoxy and the epoxy-bonded interface. This prevents us from predicting the long-term performance of the epoxy-related applications under the effect of the moisture. Here, we use full atomistic models to investigate the response of the epoxy-bonded system towards the adhesion test, and provide a detailed analysis of the interfacial integrity under the moisture effect and the associated debonding mechanism. Molecular dynamics simulations show that water molecules affect the hierarchical structure of the epoxy-bonded system at the nanoscale by disrupting the film-substrate interaction and the molecular interaction within the epoxy, which leads to the detachment of the epoxy thin film, and the final interfacial debonding. The simulation results show good agreement with the experimental results of the epoxy-bonded system. Through identifying the relationship between the epoxy structure and the debonding mechanism at multiple scales, it is shown that the hierarchical structure of the epoxy-bonded system is crucial for the interfacial integrity. In particular, the available space of the epoxy-bonded system, which consists of various sizes ranging from the atomistic scale to the macroscale and is close to the interface facilitates the moisture accumulation, leading to a distinct interfacial debonding when compared to the dry scenario.

Additive value of patch testing custom epoxy materials from the workplace at the occupational disease specialty clinic in Toronto.

PubMed

Houle, Marie-Claude; Holness, D Linn; Dekoven, Joel; Skotnicki, Sandy

2012-01-01

Allergic contact dermatitis (ACD) to epoxy resins is one of the major causes of occupationally induced ACD. Testing of custom epoxy materials from the workplace is often performed to diagnose ACD. The objective of this study was to investigate the additive value of patch testing custom-made epoxy materials. We retrospectively analyzed outcomes of 24 patients who were tested to custom epoxy resin materials between January 2002 and July 2011. For 11 patients (46%), the testing of their materials from work had no additional value (negative results). For 13 patients (54%), there was an additional value of testing custom allergens. Of those, 7 patients (54%) had positive reactions to custom epoxy materials that reinforced the test results found with the commercially available allergens, and 6 (46%) patients had positive reactions only to custom epoxy materials. Therefore, for 6 patients (25%), there was a definite additive value of testing custom epoxy materials because the allergy was discovered with custom testing and not with the commercially available allergens. Because of the high percentage (54%) of patients with additive value of patch testing custom epoxy materials, we think that the inclusion of actual workplace epoxy materials should be strongly considered when patch testing patients with occupational epoxy exposure.

Study on the Pulsed Flashover Characteristics of Solid-Solid Interface in Electrical Devices Poured by Epoxy Resin

NASA Astrophysics Data System (ADS)

Li, Manping; Wu, Kai; Yang, Zhanping; Ding, Man; Liu, Xin; Cheng, Yonghong

2014-09-01

In electrical devices poured by epoxy resin, there are a lot of interfaces between epoxy resin and other solid dielectrics, i.e. solid-solid interfaces. Experiments were carried out to study the flashover characteristics of two typical solid-solid interfaces (epoxy-ceramic and epoxy-PMMA) under steep high-voltage impulse for different electrode systems (coaxial electrodes and finger electrodes) and different types of epoxy resin (neat epoxy resin, polyether modified epoxy resin and polyurethane modified epoxy resin). Results showed that, the flashover of solid-solid interface is similar to the breakdown of solid dielectric, and there are unrecoverable carbonated tracks after flashover. Under the same distance of electrodes, the electric stress of coaxial electrodes is lower than that of finger electrodes; and after the flashover, there are more severe breakdown and larger enhanced surface conductivity at interface for coaxial electrodes, as compared with the case of finger electrode. The dielectric properties are also discussed.

Wettability of nano-epoxies to UHMWPE fibers.

PubMed

Neema, S; Salehi-Khojin, A; Zhamu, A; Zhong, W H; Jana, S; Gan, Y X

2006-07-01

Ultra high molecular weight polyethylene (UHMWPE) fibers have a unique combination of outstanding mechanical, physical, and chemical properties. However, as reinforcements for manufacturing high performance composite materials, UHMWPE fibers have poor wettability with most polymers. As a result, the interfacial bonding strength between the fibers and polymer matrices is very low. Recently, developing so-called nano-matrices containing reactive graphitic nanofibers (r-GNFs) has been proposed to promote the wetting of such matrices to certain types of fiber reinforcements. In this work, the wettability of UHMWPE fibers with different epoxy matrices including a nano-epoxy, and a pure epoxy was investigated. Systematic experimental work was conducted to determine the viscosity of the epoxies, the contact angle between the epoxies and the fibers. Also obtained are the surface energy of the fibers and the epoxies. The experimental results show that the wettability of the UHMWPE fibers with the nano-epoxy is much better than that of the UHMWPE fibers with the pure epoxy.

Thermal and Mechanical Characteristics of Polymer Composites Based on Epoxy Resin, Aluminium Nanopowders and Boric Acid

NASA Astrophysics Data System (ADS)

Nazarenko, O. B.; Melnikova, T. V.; Visakh, P. M.

2016-01-01

The epoxy polymers are characterized by low thermal stability and high flammability. Nanoparticles are considered to be effective fillers of polymer composites for improving their thermal and functional properties. In this work, the epoxy composites were prepared using epoxy resin ED-20, polyethylene polyamine as a hardener, aluminum nanopowder and boric acid fine powder as flame-retardant filler. The thermal characteristics of the obtained samples were studied using thermogravimetric analysis and differential scanning calorimetry. The mechanical characteristics of epoxy composites were also studied. It was found that an addition of all fillers enhances the thermal stability and mechanical characteristics of the epoxy composites. The best thermal stability showed the epoxy composite filled with boric acid. The highest flexural properties showed the epoxy composite based on the combination of boric acid and aluminum nanopowder.

Determinants of epoxy allergy in the construction industry: a case-control study.

PubMed

Spee, Ton; Timmerman, Johan G; Rühl, Reinhold; Kersting, Klaus; Heederik, Dick J J; Smit, Lidwien A M

2016-05-01

Workers exposed to epoxy products are at risk of developing allergic contact dermatitis. To compare workers throughout the German construction industry with and without skin allergy to epoxy resins, hardeners, and/or reactive diluents, and to investigate which determinants are related to the development of epoxy allergy. A questionnaire was completed by 179 epoxy allergy cases, and 151 epoxy workers as controls. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by the use of backwards stepwise logistic regression analysis. A multiple imputation approach was used to deal with missing data. Epoxy allergy was associated with an unusually high level of exposure to epoxy products [OR 2.13 (95%CI: 1.01-4.51)], wearing short sleeves or short trousers [OR 2.38 (95%CI: 1.03-5.52)], and not always using the correct type of gloves [OR 2.12 (95%CI: 1.12-4.01)]. A monotonic increasing risk was found with increasing exposure hours per week [OR 1.72 (95%CI: 1.39-2.14)]. Not using skin cream was inversely associated with epoxy allergy [OR 0.22 (95%CI: 0.08-0.59)]. Years working with epoxy products were inversely associated with epoxy allergy [OR 0.41 (95%CI: 0.27-0.61) per 10-year increase], suggesting a healthy worker survivor effect. Occupational epoxy allergy may be prevented by improving occupational hygiene behaviour and personal protection. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Reactions of nitriles in ices relevant to Titan, comets, and the interstellar medium: formation of cyanate ion, ketenimines, and isonitriles

NASA Astrophysics Data System (ADS)

Hudson, R. L.; Moore, M. H.

2004-12-01

Motivated by detections of nitriles in Titan's atmosphere, cometary comae, and the interstellar medium, we report laboratory investigations of the low-temperature chemistry of acetonitrile, propionitrile, acrylonitrile, cyanoacetylene, and cyanogen (CH 3CN, CH 3CH 2CN, CH 2CHCN, HCCCN, and NCCN, respectively). A few experiments were also done on isobutyronitrile and trimethylacetonitrile ((CH 3) 2CHCN and (CH 3) 3CCN, respectively). Trends were sought, and found, in the photo- and radiation chemical products of these molecules at 12-25 K. In the absence of water, all of these molecules isomerized to isonitriles, and CH 3CN, CH 3CH 2CN, and (CH 3) 2CHCN also formed ketenimines. In the presence of H 2O, no isonitriles were detected but rather the cyanate ion (OCN -) was seen in all cases. Although isonitriles, ketenimines, and OCN - were the main focus of our work, we also describe cases of hydrogen loss, to make smaller nitriles, and hydrogen addition (reduction), to make larger nitriles. HCN formation also was seen in most experiments. The results are presented in terms of nitrile ice chemistry on Titan, in cometary ice, and in the interstellar medium. Possible connections to prebiotic chemistry are briefly discussed.

4-Bromo-N-(di-n-propyl-carbamothioyl)-benzamide.

PubMed

Binzet, Gün; Flörke, Ulrich; Külcü, Nevzat; Arslan, Hakan

2009-02-04

The synthesis of the title compound, C(14)H(19)BrN(2)OS, involves the reaction of 4-bromo-benzoyl chloride with potassium thio-cyanate in acetone followed by condensation of the resulting 4-bromo-benzoyl isothio-cyanate with di-n-propyl-amine. Typical thio-urea carbonyl and thio-carbonyl double bonds, as well as shortened C-N bonds, are observed in the title compound. The short C-N bond lengths in the centre of the mol-ecule reveal the effects of resonance in this part of the mol-ecule. The asymmetric unit of the title compound contains two crystallographically independent mol-ecules, A and B. There is very little difference between the bond lengths and angles of these mol-ecules. In mol-ecule B, one di-n-propyl group is twisted in a -anti-periplanar conformation with C-C-C-H = -179.1 (3)° and the other adopts a -synclinal conformation with C-C-C-H = -56.7 (4)°; in mol-ecule A the two di-n-propyl groups are twisted in + and -anti-periplanar conformations, with C-C-C-H = -179.9 (3) and 178.2 (3)°, respectively. In the crystal, the mol-ecules are linked into dimeric pairs via pairs of N-H⋯S hydrogen bonds.

Epoxy resins in the construction industry.

PubMed

Spee, Ton; Van Duivenbooden, Cor; Terwoert, Jeroen

2006-09-01

Epoxy resins are used as coatings, adhesives, and in wood and concrete repair. However, epoxy resins can be highly irritating to the skin and are strong sensitizers. Some hardeners are carcinogenic. Based on the results of earlier Dutch studies, an international project on "best practices,"--Epoxy Code--with epoxy products was started. Partners were from Denmark, Germany, the Netherlands, and the UK. The "Code" deals with substitution, safe working procedures, safer tools, and skin protection. The feasibility of an internationally agreed "ranking system" for the health risks of epoxy products was studied. Such a ranking system should inform the user of the harmfulness of different epoxies and stimulate research on less harmful products by product developers.

Occupational dermatoses from exposure to epoxy resin compounds in a ski factory.

PubMed

Jolanki, R; Tarvainen, K; Tatar, T; Estlander, T; Henriks-Eckerman, M L; Mustakallio, K K; Kanerva, L

1996-06-01

Of 22 workers in a ski factory, occupational allergic contact dermatitis was found in 8. 6 were sensitive to epoxy resin compounds, i.e., epoxy resins, hardeners or diluents, 1 to cobalt in glass-fiber reinforcements, and 1 to formaldehyde in a urea-formaldehyde glue and a lacquer. 4 workers had irritant contact dermatitis from epoxy resin compounds, lacquers, sanding dust, or glass-fiber dust. 3 had contact allergy from a new sensitizer, diethyleneglycol diglycidyl ether, in a reactive diluent. Immediate transfer of workers sensitized to epoxy resin from epoxy exposure prevents aggravation of their dermatitis and broadening of the sensitization to epoxy hardeners, diluents and other compounds.

Flame Retardant Epoxy Resins

NASA Technical Reports Server (NTRS)

Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.

2004-01-01

As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.

Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity.

PubMed

Xu, Yonggang; Yang, Chi; Li, Jun; Mao, Xiaojian; Zhang, Hailong; Hu, Song; Wang, Shiwei

2017-12-18

AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity.

Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity

PubMed Central

Xu, Yonggang; Yang, Chi; Li, Jun; Zhang, Hailong; Hu, Song; Wang, Shiwei

2017-01-01

AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity. PMID:29258277

Poly(arylene ether-co-imidazole)s as toughness modifiers for epoxy resins

NASA Technical Reports Server (NTRS)

Mcdaniel, Patricia D. (Inventor); Connell, John W. (Inventor)

1994-01-01

A toughened epoxy was prepared by reacting an epoxy resin with a poly(arylene ether-co-imidazole)s (PAEI). The epoxy resin comprises N,N,N',N'tetraglycidyl-4,4'- methylenebisbenzenamine and 4-aminophenyl sulfone. The PAEI was prepared by reacting an aromatic bisphenol, a bisphenol imidazole, and an activated aromatic dihalide or dinitro compound in the presence of potassium carbonate in a polar aprotic solvent at an elevated temperature. The epoxies which were modified with these particular PAEI's showed a significant increase in toughness with only a 10 weight percent loading of the PAEI into the epoxy. These toughened epoxies were used to prepare composites and molded parts.

Enhanced Flexural Strength of Tellurium Nanowires/epoxy Composites with the Reinforcement Effect of Nanowires

NASA Astrophysics Data System (ADS)

Balguri, Praveen Kumar; Harris Samuel, D. G.; Aditya, D. B.; Vijaya Bhaskar, S.; Thumu, Udayabhaskararao

2018-02-01

Investigating the mechanical properties of polymer nanocomposite materials has been greatly increased in the last decade. In particular, flexural strength plays a major role in resisting bending and shear loads of a composite material. Here, one dimensional (1D) tellurium nanowires (TeNWs) reinforced epoxy composites have been prepared and the flexural properties of resulted TeNWs/epoxy nanocomposites are studied. The diameter and length of the TeNWs used to make TeNWs/epoxy nanocomposites are 21±2.5 nm and 697±87 nm, respectively. Plain and TeNWs/epoxy nanocomposites are characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Furthermore, significant enhancement in the flexural strength of TeNWs/epoxy nanocomposite is observed in comparison to plain epoxy composite, i.e. flexural strength is increased by 65% with the addition of very little amount of TeNWs content (0.05 wt.%) to epoxy polymer. Structural details of plain and TeNWs/epoxy at micrometer scale were examined by scanning electron microscopy (SEM). We believe that our results provide a new type of semiconductor nanowires based high strength epoxy polymer nanocomposites.

Quantitative Study of Interface/Interphase in Epoxy/Graphene-Based Nanocomposites by Combining STEM and EELS.

PubMed

Liu, Yu; Hamon, Ann-Lenaig; Haghi-Ashtiani, Paul; Reiss, Thomas; Fan, Benhui; He, Delong; Bai, Jinbo

2016-12-14

A quantitative study of the interphase and interface of graphene nanoplatelets (GNPs)/epoxy and graphene oxide (GO)/epoxy was carried out by combining scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). The interphase regions between GNPs and epoxy matrix were clearly identified by the discrepancy of the plasmon peak positions in the low energy-loss spectra due to different valence electron densities. The spectrum acquisitions were carried out along lines across the interface. An interphase thickness of 13 and 12.5 nm was measured for GNPs/epoxy and GO/epoxy, respectively. The density of the GNPs/epoxy interphase was 2.89% higher than that of the epoxy matrix. However, the density of the GO/epoxy interphase was 1.37% lower than that of the epoxy matrix. The interphase layer thickness measured in this work is in good agreement with the transition layer theory, which proposed an area with modulus linearly varying across a finite width. The results provide an insight into the interphase for carbon-based polymer composites that can help to design the functionalization of nanofillers to improve the composite properties.

Mechanical Properties of Epoxy Resin Mortar with Sand Washing Waste as Filler.

PubMed

Yemam, Dinberu Molla; Kim, Baek-Joong; Moon, Ji-Yeon; Yi, Chongku

2017-02-28

The objective of this study was to investigate the potential use of sand washing waste as filler for epoxy resin mortar. The mechanical properties of four series of mortars containing epoxy binder at 10, 15, 20, and 25 wt. % mixed with sand blended with sand washing waste filler in the range of 0-20 wt. % were examined. The compressive and flexural strength increased with the increase in epoxy and filler content; however, above epoxy 20 wt. %, slight change was seen in strength due to increase in epoxy and filler content. Modulus of elasticity also linearly increased with the increase in filler content, but the use of epoxy content beyond 20 wt. % decreased the modulus of elasticity of the mortar. For epoxy content at 10 wt. %, poor bond strength lower than 0.8 MPa was observed, and adding filler at 20 wt. % adversely affected the bond strength, in contrast to the mortars containing epoxy at 15, 20, 25 wt. %. The results indicate that the sand washing waste can be used as potential filler for epoxy resin mortar to obtain better mechanical properties by adding the optimum level of sand washing waste filler.

Mechanical Properties of Epoxy Resin Mortar with Sand Washing Waste as Filler

PubMed Central

Yemam, Dinberu Molla; Kim, Baek-Joong; Moon, Ji-Yeon; Yi, Chongku

2017-01-01

The objective of this study was to investigate the potential use of sand washing waste as filler for epoxy resin mortar. The mechanical properties of four series of mortars containing epoxy binder at 10, 15, 20, and 25 wt. % mixed with sand blended with sand washing waste filler in the range of 0–20 wt. % were examined. The compressive and flexural strength increased with the increase in epoxy and filler content; however, above epoxy 20 wt. %, slight change was seen in strength due to increase in epoxy and filler content. Modulus of elasticity also linearly increased with the increase in filler content, but the use of epoxy content beyond 20 wt. % decreased the modulus of elasticity of the mortar. For epoxy content at 10 wt. %, poor bond strength lower than 0.8 MPa was observed, and adding filler at 20 wt. % adversely affected the bond strength, in contrast to the mortars containing epoxy at 15, 20, 25 wt. %. The results indicate that the sand washing waste can be used as potential filler for epoxy resin mortar to obtain better mechanical properties by adding the optimum level of sand washing waste filler. PMID:28772603

Salt exclusion in silane-laced epoxy coatings.

PubMed

Wang, Peng; Schaefer, Dale W

2010-01-05

The corrosion protection mechanism of a one-step silane-laced epoxy coating system was investigated using neutron reflectivity. Pure epoxy and silane-laced epoxy films were examined at equilibrium with saturated NaCl water solution. The results demonstrate that the addition of silane introduces a salt-exclusion effect to epoxy coating. Specifically, the addition of silane densifies the epoxy network, which leads to exclusion of hydrated salt ions by a size effect. The effect is particularly significant at the metal-coating interface. Exclusion of ions improves the corrosion resistance, particularly for metals susceptible to pitting.

Can simultaneous contact allergies to phenyl glycidyl ether and epoxy resins of the bisphenol A/F-types be explained by contamination of the epoxy resins?

PubMed

Pontén, Ann; Zimerson, Erik; Bruze, Magnus

2008-11-01

Simultaneous contact allergies to epoxy resins based on diglycidyl ether of bisphenol A (DGEBA-R) or epoxy resins of the bisphenol F-type and the reactive diluent phenyl glycidyl ether (PGE) have been reported. The reason might be cross-reactivity, exposure to an epoxy resin system with PGE as a component, or contamination by PGE in the epoxy resin. To study contamination by PGE, 20 commercial epoxy resins were analysed for the presence of PGE. To study contact allergy to PGE and its relation to epoxy resins by inserting PGE in the standard series. Among 2227 patients, 7 reacted to PGE. Of 23 (30%) patients, 7 with contact allergy to DGEBA-R and 7/19 (37%) with contact allergy to an epoxy resin of the bisphenol F-type reacted to PGE. All 7 patients with contact allergy to PGE reacted both to the DGEBA-R and to the epoxy resin of the bisphenol F-type. PGE was found in 90% of the investigated resins. The amounts of PGE ranged between 0.004% w/w and 0.18% w/w. Most probably, the presence of PGE as a contaminant in epoxy resins is of minor importance for the sensitization, but possibly the contamination of PGE might elicit contact dermatitis in individuals with a high reactivity to PGE.

Contact allergy to epoxy resin: risk occupations and consequences.

PubMed

Bangsgaard, Nannie; Thyssen, Jacob Pontoppidan; Menné, Torkil; Andersen, Klaus Ejner; Mortz, Charlotte G; Paulsen, Evy; Sommerlund, Mette; Veien, Niels Kren; Laurberg, Grete; Kaaber, Knud; Thormann, Jens; Andersen, Bo Lasthein; Danielsen, Anne; Avnstorp, Christian; Kristensen, Berit; Kristensen, Ove; Vissing, Susanne; Nielsen, Niels Henrik; Johansen, Jeanne Duus

2012-08-01

Epoxy resin monomers are strong skin sensitizers that are widely used in industrial sectors. In Denmark, the law stipulates that workers must undergo a course on safe handling of epoxy resins prior to occupational exposure, but the effectiveness of this initiative is largely unknown. To evaluate the prevalence of contact allergy to epoxy resin monomer (diglycidyl ether of bisphenol A; MW 340) among patients with suspected contact dermatitis and relate this to occupation and work-related consequences. The dataset comprised 20 808 consecutive dermatitis patients patch tested during 2005-2009. All patients with an epoxy resin-positive patch test were sent a questionnaire. A positive patch test reaction to epoxy resin was found in 275 patients (1.3%), with a higher proportion in men (1.9%) than in women (1.0%). The prevalence of sensitization to epoxy resin remained stable over the study period. Of the patients with an epoxy resin-positive patch test, 71% returned a questionnaire; 95 patients had worked with epoxy resin in the occupational setting, and, of these, one-third did not use protective gloves and only 50.5% (48) had participated in an educational programme. The 1% prevalence of epoxy resin contact allergy is equivalent to reports from other countries. The high occurrence of epoxy resin exposure at work, and the limited use of protective measures, indicate that reinforcement of the law is required. © 2012 John Wiley & Sons A/S.

Advanced Design Composite Aircraft

DTIC Science & Technology

1976-02-01

been selected for ADCA applications. These are graphite (PAN)/ epoxy, graphite (PAN)/polyimide, Kevlar /epoxy, f ibergl ass/epoxy, and quartz...Aluminum Alloy Aluminum Alloy ACG (commercial grade) Nomex HRP Fiberglass/ Phenolic HRH Fiberglass/Polyimide Graphite/epoxy Graphi te/Polyimide

Heat Loads Due to Small Penetrations in Multilayer Insulation Blankets

NASA Technical Reports Server (NTRS)

Johnson, W. L.; Heckle, K. W.; Fesmire, J. E.

2017-01-01

Abstract: This paper covers cryogenic, tensile testing and research completed on a number of epoxies used in cryogenic applications. Epoxies are used in many different applications; however, this research focused on the use of epoxy used to bond MLI standoffs to cryogenic storage tanks and the loads imparted to the tank through the MLI. To conduct testing, samples were made from bare stainless steel, aluminum and primed aluminum. Testing involved slowly cooling test samples with liquid nitrogen then applying gradually increasing tensile loads to the epoxy. The testing evaluated the strength and durability of epoxies at cryogenic temperatures and serves as a base for future testing. The results of the tests showed that some epoxies withstood the harsh conditions while others failed. The two epoxies yielding the best results were Masterbond EP29LPSP and Scotch Weld 2216. For all metal surfaces tested, both epoxies had zero failures for up to 11.81 kg of mass.

Rubber-Modified Epoxies. I. Cure, Transitions, and Morphology.

DTIC Science & Technology

1984-10-01

thermosetting systems has been developed. An aromatic tetrafunctional diamine-cured diglycidyl ether of bis- phenol A epoxy resin [maximum glass transition...systems has been developed. An aromatic tetrafunctional diamine-cured digly- cidyl ether of bisphenol A epoxy resin [maximum glass transition...epoxy resins are brittle materials. The crack resistance can be improved by the addition of reactive liquid rubber to uncured neat epoxy systems (1-3

Flammability of Epoxy Resins Containing Phosphorus

NASA Technical Reports Server (NTRS)

Hergenrother, P. M.; Thompson, C. M.; Smith, J. G.; Connell, J. W.; Hinkley, J. A.

2005-01-01

As part of a program to develop fire-resistant exterior composite structures for future subsonic commercial and general aviation aircraft, flame-retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured neat epoxy formulations were characterized by thermogravimetric analysis, propane torch test, elemental analysis, microscale combustion calorimetry, and fire calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness and compressive strength of several cured formulations showed no detrimental effect due to phosphorus content. The chemistry and properties of these new epoxy formulations are discussed.

Selective Clay Placement Within a Silicate-Clay Epoxy Blend Nanocomposite

NASA Technical Reports Server (NTRS)

Miller, Sandi G (Inventor)

2013-01-01

A clay-epoxy nanocomposite may be prepared by dispersing a layered clay in an alkoxy epoxy, such as a polypropylene oxide based epoxide before combining the mixture with an aromatic epoxy to improve the nanocomposite's thermal and mechanical properties.

Evaluation of epoxy systems for use in SBASI

NASA Technical Reports Server (NTRS)

Coultas, T. J.

1971-01-01

The purpose of the test program was to evaluate the performance of different epoxy systems as replacements for existing epoxy systems in the SBASI. The three areas of investigation were the connector shell potting, the epoxy tape under the charge cup, and the epoxy impregnated fiberglass over the output charge. Factors considered, in addition to performance, were availability, shelf life, pot life, and effect on producibility and cost.

Regeneration efficiency, shuttle heat loss and thermal conductivity in epoxy-composite annualr gap regenerators from 4K to 80K

NASA Technical Reports Server (NTRS)

Myrtle, K.; Cygax, S.; Plateel, C.; Winter, C.

1983-01-01

A test apparatus designed to simulate a section of a Stirling cycle cryocooler was built. Measurements of regeneration efficiency, shuttle heat loss and thermal conductivity reported for several regenerator test sections. The test composites were epoxy glass, epoxy glass with lead particles, epoxy glass with activated charcoal and epoxy graphite. Losses measured for these materials were approximately the same. Losses are in good agreement with those calculated theoretically for an epoxy glass (C-10) composite. The implications of these results on cryocooler design are discussed.

Cross-Sectional Study of Respiratory Symptoms, Spirometry, and Immunologic Sensitivity in Epoxy Resin Workers.

PubMed

Hines, Stella E; Barker, Elizabeth A; Robinson, Maura; Knight, Vijaya; Gaitens, Joanna; Sills, Michael; Duvall, Kirby; Rose, Cecile S

2015-12-01

An epoxy resin worker developed hypersensitivity pneumonitis requiring lung transplantation and had an abnormal blood lymphocyte proliferation test (LPT) to an epoxy hardener. We assessed the prevalence of symptoms, abnormal spirometry, and abnormal epoxy resin LPT results in epoxy resin workers compared to unexposed workers. Participants completed questionnaires and underwent spirometry. We collected blood for epoxy resin LPT and calculated stimulation indices for five epoxy resin products. We compared 38 exposed to 32 unexposed workers. Higher exposed workers were more likely to report cough (OR 10.86, [1.23-infinity], p = 0.030) or wheeze (OR 4.44, [1.00-22.25], p = 0.049) than unexposed workers, even controlling for smoking. Higher exposed workers were more likely to have abnormal FEV1 than unexposed workers (OR 10.51, [0.86-589.9], p = 0.071), although not statistically significant when adjusted for smoking. There were no differences in proportion of abnormal epoxy resin system LPTs between exposed and unexposed workers. In summary, workers exposed to epoxy resin system chemicals were more likely to report respiratory symptoms and have abnormal FEV1 than unexposed workers. Use of epoxy resin LPT was not helpful as a biomarker of exposure and sensitization. © 2015 Wiley Periodicals, Inc.

Cross‐Sectional Study of Respiratory Symptoms, Spirometry, and Immunologic Sensitivity in Epoxy Resin Workers

PubMed Central

Barker, Elizabeth A.; Robinson, Maura; Knight, Vijaya; Gaitens, Joanna; Sills, Michael; Duvall, Kirby; Rose, Cecile S.

2015-01-01

Abstract Objectives An epoxy resin worker developed hypersensitivity pneumonitis requiring lung transplantation and had an abnormal blood lymphocyte proliferation test (LPT) to an epoxy hardener. We assessed the prevalence of symptoms, abnormal spirometry, and abnormal epoxy resin LPT results in epoxy resin workers compared to unexposed workers. Methods Participants completed questionnaires and underwent spirometry. We collected blood for epoxy resin LPT and calculated stimulation indices for five epoxy resin products. Results We compared 38 exposed to 32 unexposed workers. Higher exposed workers were more likely to report cough (OR 10.86, [1.23‐infinity], p = 0.030) or wheeze (OR 4.44, [1.00‐22.25], p = 0.049) than unexposed workers, even controlling for smoking. Higher exposed workers were more likely to have abnormal FEV1 than unexposed workers (OR 10.51, [0.86‐589.9], p = 0.071), although not statistically significant when adjusted for smoking. There were no differences in proportion of abnormal epoxy resin system LPTs between exposed and unexposed workers. Conclusions In summary, workers exposed to epoxy resin system chemicals were more likely to report respiratory symptoms and have abnormal FEV1 than unexposed workers. Use of epoxy resin LPT was not helpful as a biomarker of exposure and sensitization. PMID:26553118

Mechanical, morphological and structural properties of cellulose nanofibers reinforced epoxy composites.

PubMed

Saba, N; Mohammad, F; Pervaiz, M; Jawaid, M; Alothman, O Y; Sain, M

2017-04-01

Present study, deals about isolation and characterization of cellulose nanofibers (CNFs) from the Northern Bleached Softwood Kraft (NBSK) pulp, fabrication by hand lay-up technique and characterization of fabricated epoxy nanocomposites at different filler loadings (0.5%, 0.75%, 1% by wt.). The effect of CNFs loading on mechanical (tensile, impact and flexural), morphological (scanning electron microscope and transmission electron microscope) and structural (XRD and FTIR) properties of epoxy composites were investigated. FTIR analysis confirms the introduction of CNFs into the epoxy matrix while no considerable change in the crystallinity and diffraction peaks of epoxy composites were observed by the XRD patterns. Additions of CNFs considerably enhance the mechanical properties of epoxy composites but a remarkable improvement is observed for 0.75% CNFs as compared to the rest epoxy nanocomposites. In addition, the electron micrographs revealed the perfect distribution and dispersion of CNFs in the epoxy matrix for the 0.75% CNFs/epoxy nanocomposites, while the existence of voids and agglomerations were observed beyond 0.75% CNFs filler loadings. Overall results analysis clearly revealed that the 0.75% CNFs filler loading is best and effective with respect to rest to enhance the mechanical and structural properties of the epoxy composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Montmorillonite Nanogel Composite Fillers on the Protection Performance of Epoxy Coatings on Steel Pipelines.

PubMed

Atta, Ayman M; El-Saeed, Ashraf M; Al-Lohedan, Hamad A; Wahby, Mohamed

2017-06-02

Montmorillonite (MMT) clay mineral is widely used as filler for several organic coatings. Its activity is increased by exfoliation via chemical modification to produce nanomaterials. In the present work, the modification of MMT to form nanogel composites is proposed to increase the dispersion of MMT into epoxy matrices used to fill cracks and holes produced by the curing exotherms of epoxy resins. The dispersion of MMT in epoxy improved both the mechanical and anti-corrosion performance of epoxy coatings in aggressive marine environments. In this respect, the MMT surfaces were chemically modified with different types of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) nanogels using a surfactant-free dispersion polymerization technique. The effect of the chemical structure, nanogel content and the interaction with MMT surfaces on the surface morphology, surface charges and dispersion in the epoxy matrix were investigated for use as nano-filler for epoxy coatings. The modified MMT nanogel epoxy composites showed excellent resistance to mechanical damage and salt spray resistance up to 1000 h. The interaction of MMT nanogel composites with the epoxy matrix and good response of AMPS nanogel to sea water improve their ability to act as self-healing materials for epoxy coatings for steel.

Biobased Epoxy Nanocomposites Derived from Lignin-Based Monomers.

PubMed

Zhao, Shou; Abu-Omar, Mahdi M

2015-07-13

Biobased epoxy nanocomposites were synthesized based on 2-methoxy-4-propylphenol (dihydroeugenol, DHE), a molecule that has been obtained from the lignin component of biomass. To increase the content of hydroxyl groups, DHE was o-demethylated using aqueous HBr to yield propylcatechol (DHEO), which was subsequently glycidylated to epoxy monomer. Optimal conditions in terms of yield and epoxy equivalent weight were found to be 60 °C with equal NaOH/phenolic hydroxyl molar ratio. The structural evolution from DHE to cured epoxy was followed by (1)H NMR and Fourier transform infrared spectroscopy. The nano-montmorillonite modified DHEO epoxy exhibited improved storage modulus and thermal stability as determined from dynamic mechanical analysis and thermogravimetric analysis. This study widens the synthesis routes of biobased epoxy thermosets from lignin-based molecules.

Epoxy thermoset networks derived from vegetable oils and their blends

NASA Astrophysics Data System (ADS)

Ryu, Chang; Ravalli, Matthew

2015-03-01

Epoxidized vegetable oils (EVOs), such as epoxidized soybean oil and linseed oils were prepared by the partial oxidation of the unsaturated double bonds in vegetable oils and used as monomers for preparing epoxy thermoset materials based on the cationic polymerization. These EVOs have been used to prepare epoxy thermosets of different network densities by cationic polymerization using onium salt catalyst. The crosslinked epoxy thermosets provide an ideal platform to study the structure-property-relationships of networked polymers. In particular, rheological studies on the epoxidized vegetable oil thermosets have been performed to measure the molecular weights between crosslinks (Mx) in the epoxy thermosets and to ultimately elucidate the role of functionality of epoxy groups in EVO on the mechanical and thermophysical properties of the epoxy thermoset materials. NSF DMR POLYMERS 1308617.

Anti-flammable vinyl ester resin nano-composite with nano-titania

NASA Astrophysics Data System (ADS)

Das, Rajib

Anti-flammable material is a common expectation for any industry and household applications to protect the material from fire accident. Polymer composites also play a significant role in preparing anti flammable materials. Vinyl ester resins (VERs) are thermosetting resins that have excellent mechanical and thermal properties of epoxy resins and Nanotitania is an inexpensive, nontoxic and biocompatible inorganic material. In this paper to investigate the flame retardency of polymer nanocomposites VER is used as polymer matrix and TiO2 is used as inorganic nanofiller.3-[2-(2-aminoethylamino) ethylamino]propyl-trimethoxysilane (TATMS), a kind of silane is used as a coupling agent to functionalize the surface of nanoTiO2 to improve its flame retardency by adding Si and N2 group. TGA test and FTIR test have been performed and different peaks for Si and N2 in the modified nanofiller and weight loss of fabricated nanofiller confirmed that fabrication method was successful. After that, nanocomposite sample of VERs reinforced with nano TiO2 prepared and the effects of different loadings on mechanical and flame retardant properties are investigated after and before the modification of nanofillers. From tensile test result it is found that up to 5% loading of modified nanofiller the tensile strength is 62 MPa that is almost as same as pure VER and the tensile strength of unmodified nanofiller based PNC is 68 MPa which is not significant improvement in its mechanical property. From MCC test of flame retardancy it is found that the normalized heat release capacity of modified nanofiller based nanocomposite is decreased by 27.7% than unmodified nanofiller based PNC that is 9.8%. Also the normalized total heat release of modified nanofiller based PNC is 21.4% than unmodified PNC that is 12.4%.

High performance bio-based thermosets for composites and coatings

NASA Astrophysics Data System (ADS)

Paramarta, Adlina Ambeg

In the recent decade, there has been increasing interest in using renewable feedstocks as chemical commodities for composites and coatings application. Vegetable oils are promising renewable resources due to their wide availability with affordable cost. In fact, the utilization of vegetable oils to produce composite and coatings products has been around for centuries; linseed oil was widely used for wide variety of paints. However, due to its chemical structure, the application of vegetable oils for high-performance materials is limited; and thus chemical modification is necessary. One of the modification approaches is by substituting the glycerol core in the triglycerides with sucrose to form sucrose esters of vegetable oil fatty acids, in which this resin possesses a higher number of functional group per molecule and a more rigid core. In this research, thermosets of highly functionalized sucrose esters of vegetable oils were developed. Two crosslinking methods of epoxidized surcrose soyate (ESS) resins were explored: direct polymerization with anhydride moieties for composite applications and Michael-addition reaction of acrylated-epoxidized sucrose soyate (AESS) for coatings applications. In the first project, it was shown that the reaction kinetics, thermal and mechanical properties of the materials can be tuned by varying the molar ratio between the epoxide and anhydride, plus the type and amount of catalyst. Furthermore, the toughness properties of the ESS-based thermosets can be improved by changing the type of anhydride crosslinkers and incorporating secondary phase rubbers. Then, in the second system, the epoxy functionality in the ESS was converted into acrylate group, which then crosslinked with amine groups through the Michael-addition reaction to produce coatings systems. The high number of functional groups and the fast reactivity of the crosslinker results in coatings that can be cured at ambient temperature, yet still possess moderately high glass transition temperatures.

The Effect of High Concentration and Small Size of Nanodiamonds on the Strength of Interface and Fracture Properties in Epoxy Nanocomposite

PubMed Central

Haleem, Yasir A.; Song, Pin; Liu, Daobin; Wang, Changda; Gan, Wei; Saleem, Muhammad Farooq; Song, Li

2016-01-01

The concentration and small size of nanodiamonds (NDs) plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites. It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy. Rationally, functionalized-NDs (F-NDs) showed a much better performance for the nanocomposite than pristine NDs (P-NDs) because of additional functional groups on its surface. The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy, indicating the presence of a strong interface. We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web, which can efficiently hinder further crack propagation. In addition, the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles, whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface. Because of the strong interface in F-ND/epoxy nanocomposites, at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks, parallel to the parent crack, via crack splitting which results in a fiber-like structure on the fracture surface. The plastic void growth, crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites. PMID:28773628

Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites

NASA Astrophysics Data System (ADS)

Fasanella, Nicholas A.; Sundararaghavan, Veera

2016-05-01

The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.

Rodent Biocompatibility Test Using the NASA Foodbar and Epoxy EP21LV

NASA Technical Reports Server (NTRS)

Tillman, J.; Steele, M.; Dumars, P.; Vasques, M.; Girten, B.; Sun, S. (Technical Monitor)

2002-01-01

Epoxy has been used successfully to affix NASA foodbars to the inner walls of the Animal Enclosure Module for past space flight experiments utilizing rodents. The epoxy used on past missions was discontinued, making it necessary to identify a new epoxy for use on the STS-108 and STS-107 missions. This experiment was designed to test the basic biocompatibility of epoxy EP21LV with male rats (Sprague Dawley) and mice (Swiss Webster) when applied to NASA foodbars. For each species, the test was conducted with a control group fed untreated foodbars and an experimental group fed foodbars applied with EP21LV. For each species, there were no group differences in animal health and no statistical differences (P<0.05) in body weights throughout the study. In mice, there was a 16% increase in heart weight in the epoxy group; this result was not found in rats. For both species, there were no statistical differences found in other organ weights measured. In rats, blood glucose levels were 15% higher and both total protein and globulin were 10% lower in the epoxy group. Statistical differences in these parameters were not found in mice. For both species, no statistical differences were found in other blood parameters tested. Food consumption was not different in rats but water consumption was significantly decreased 10 to 15% in the epoxy group. The difference in water consumption is likely due to an increased water content of the epoxy-treated foodbars. Finally, both species avoided consumption of the epoxy material. Based on the global analysis of the results, the few parameters found to be statistically different do not appear to be a physiologically relevant effect of the epoxy material, We conclude that the EP21LV epoxy is biocompatible with rodents.

The Effect of High Concentration and Small Size of Nanodiamonds on the Strength of Interface and Fracture Properties in Epoxy Nanocomposite.

PubMed

Haleem, Yasir A; Song, Pin; Liu, Daobin; Wang, Changda; Gan, Wei; Saleem, Muhammad Farooq; Song, Li

2016-06-23

The concentration and small size of nanodiamonds (NDs) plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites. It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy. Rationally, functionalized-NDs (F-NDs) showed a much better performance for the nanocomposite than pristine NDs (P-NDs) because of additional functional groups on its surface. The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy, indicating the presence of a strong interface. We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web, which can efficiently hinder further crack propagation. In addition, the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles, whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface. Because of the strong interface in F-ND/epoxy nanocomposites, at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks, parallel to the parent crack, via crack splitting which results in a fiber-like structure on the fracture surface. The plastic void growth, crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites.

Biomolecules from HCN

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Wos, J. D.; Ryan, T. J.; Lobo, A. P.; Donner, D. B.

1974-01-01

It has been suggested by Sanchez et al. (1967) that HCN might have been one of the more important precursors of biological molecules on the primitive earth. Studies were conducted to determine the mechanisms involved in HCN oligomerizations in dilute aqueous solutions and to identify the compounds which are produced in these oligomerization mixtures. Indirect evidence for the formation of cyanate was obtained along with direct evidence for the formation of citrulline, aspartic acid, and orotic acid.

Thermal Characterization and Flammability of Structural Epoxy Adhesive and Carbon/Epoxy Composite with Environmental and Chemical Degradation (Postprint)

DTIC Science & Technology

2012-01-01

this study). TGA scans show the thermal degradation of carbon/ epoxy composite by fuel additive at room temperature. Through Microscale Combustion...concerns regarding the durability of structural epoxy adhesive contaminated by hydraulic fluid or fuel additive , under simplified test conditions (no...higher than room tem- perature) or fuel additive (at all temperatures of this study). TGA scans show the thermal degradation of carbon/ epoxy composite

40 CFR 721.2755 - Cycloaliphatic epoxy resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cycloaliphatic epoxy resin (generic... Substances § 721.2755 Cycloaliphatic epoxy resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as cycloaliphatic epoxy resin (PMN...

40 CFR 721.2755 - Cycloaliphatic epoxy resin (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cycloaliphatic epoxy resin (generic... Substances § 721.2755 Cycloaliphatic epoxy resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as cycloaliphatic epoxy resin (PMN...

40 CFR 721.2755 - Cycloaliphatic epoxy resin (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Cycloaliphatic epoxy resin (generic... Substances § 721.2755 Cycloaliphatic epoxy resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as cycloaliphatic epoxy resin (PMN...

40 CFR 721.2755 - Cycloaliphatic epoxy resin (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cycloaliphatic epoxy resin (generic... Substances § 721.2755 Cycloaliphatic epoxy resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as cycloaliphatic epoxy resin (PMN...

40 CFR 721.2755 - Cycloaliphatic epoxy resin (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cycloaliphatic epoxy resin (generic... Substances § 721.2755 Cycloaliphatic epoxy resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as cycloaliphatic epoxy resin (PMN...

Effect of electron beam irradiation on thermal and mechanical properties of aluminum based epoxy composites

NASA Astrophysics Data System (ADS)

Visakh, P. M.; Nazarenko, O. B.; Sarath Chandran, C.; Melnikova, T. V.; Nazarenko, S. Yu.; Kim, J.-C.

2017-07-01

The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

Enhancing the Heat Transfer Efficiency in Graphene-Epoxy Nanocomposites Using a Magnesium Oxide-Graphene Hybrid Structure.

PubMed

Du, Fei-Peng; Yang, Wen; Zhang, Fang; Tang, Chak-Yin; Liu, Sheng-Peng; Yin, Le; Law, Wing-Cheung

2015-07-08

Composite materials, such as organic matrices doped with inorganic fillers, can generate new properties that exhibit multiple functionalities. In this paper, an epoxy-based nanocomposite that has a high thermal conductivity and a low electrical conductivity, which are required for the use of a material as electronic packaging and insulation, was prepared. The performance of the epoxy was improved by incorporating a magnesium oxide-coated graphene (MgO@GR) nanomaterial into the epoxy matrix. We found that the addition of a MgO coating not only improved the dispersion of the graphene in the matrix and the interfacial bonding between the graphene and epoxy but also enhanced the thermal conductivity of the epoxy while preserving the electrical insulation. By adding 7 wt % MgO@GR, the thermal conductivity of the epoxy nanocomposites was enhanced by 76% compared with that of the neat epoxy, and the electrical resistivity was maintained at 8.66 × 10(14) Ω m.

Epoxy composite dusts with and without carbon nanotubes cause similar pulmonary responses, but differences in liver histology in mice following pulmonary deposition.

PubMed

Saber, Anne Thoustrup; Mortensen, Alicja; Szarek, Józef; Koponen, Ismo Kalevi; Levin, Marcus; Jacobsen, Nicklas Raun; Pozzebon, Maria Elena; Mucelli, Stefano Pozzi; Rickerby, David George; Kling, Kirsten; Atluri, Rambabu; Madsen, Anne Mette; Jackson, Petra; Kyjovska, Zdenka Orabi; Vogel, Ulla; Jensen, Keld Alstrup; Wallin, Håkan

2016-06-29

The toxicity of dusts from mechanical abrasion of multi-walled carbon nanotube (CNT) epoxy nanocomposites is unknown. We compared the toxic effects of dusts generated by sanding of epoxy composites with and without CNT. The used CNT type was included for comparison. Mice received a single intratracheal instillation of 18, 54 and 162 μg of CNT or 54, 162 and 486 μg of the sanding dust from epoxy composite with and without CNT. DNA damage in lung and liver, lung inflammation and liver histology were evaluated 1, 3 and 28 days after intratracheal instillation. Furthermore, the mRNA expression of interleukin 6 and heme oxygenase 1 was measured in the lungs and serum amyloid A1 in the liver. Printex 90 carbon black was included as a reference particle. Pulmonary exposure to CNT and all dusts obtained by sanding epoxy composite boards resulted in recruitment of inflammatory cells into lung lumen: On day 1 after instillation these cells were primarily neutrophils but on day 3, eosinophils contributed significantly to the cell population. There were still increased numbers of neutrophils 28 days after intratracheal instillation of the highest dose of the epoxy dusts. Both CNT and epoxy dusts induced DNA damage in lung tissue up to 3 days after intratracheal instillation but not in liver tissue. There was no additive effect of adding CNT to epoxy resins for any of the pulmonary endpoints. In livers of mice instilled with CNT and epoxy dust with CNTs inflammatory and necrotic histological changes were observed, however, not in mice instilled with epoxy dust without CNT. Pulmonary deposition of epoxy dusts with and without CNT induced inflammation and DNA damage in lung tissue. There was no additive effect of adding CNT to epoxies for any of the pulmonary endpoints. However, hepatic inflammatory and necrotic histopathological changes were seen in mice instilled with sanding dust from CNT-containing epoxy but not in mice instilled with reference epoxy.

Method of making thermally removable epoxies

DOEpatents

Loy, Douglas A.; Wheeler, David R.; Russick, Edward M.; McElhanon, James R.; Saunders, Randall S.

2002-01-01

A method of making a thermally-removable epoxy by mixing a bis(maleimide) compound to a monomeric furan compound containing an oxirane group to form a di-epoxy mixture and then adding a curing agent at temperatures from approximately room temperature to less than approximately 90.degree. C. to form a thermally-removable epoxy. The thermally-removable epoxy can be easily removed within approximately an hour by heating to temperatures greater than approximately 90.degree. C. in a polar solvent. The epoxy material can be used in protecting electronic components that may require subsequent removal of the solid material for component repair, modification or quality control.

Preparation, Characterization, and Enhanced Thermal and Mechanical Properties of Epoxy-Titania Composites

PubMed Central

Rubab, Zakya; Siddiqi, Humaira M.; Saeed, Shaukat

2014-01-01

This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress. PMID:24578638

Statistical Investigation of the Effect of Process Parameters on the Shear Strength of Metal Adhesive Joints

NASA Astrophysics Data System (ADS)

Rajkumar, Goribidanur Rangappa; Krishna, Munishamaih; Narasimhamurthy, Hebbale Narayanrao; Keshavamurthy, Yalanabhalli Channegowda

2017-06-01

The objective of the work was to optimize sheet metal joining parameters such as adhesive material, adhesive thickness, adhesive overlap length and surface roughness for single lap joint of aluminium sheet shear strength using robust design. An orthogonal array, main effect plot, signal-to-noise ratio and analysis of variance were employed to investigate the shear strength of the joints. The statistical result shows vinyl ester is best candidate among other two polymers viz. epoxy and polyester due to its low viscosity value compared to other two polymers. The experiment results shows that the adhesive thickness 0.6 mm, overlap length 50 mm and surface roughness 2.12 µm for obtained maximum shear strength of Al sheet joints. The ANOVA result shows one of the most significant factors is overlap length which affect joint strength in addition to adhesive thickness, adhesive material, and surface roughness. A confirmation test was carried out as the optimal combination of parameters will not match with the any of the experiments in the orthogonal array.

Sesquiterpenes from Neurolaena lobata and their antiproliferative and anti-inflammatory activities.

PubMed

Lajter, Ildikó; Vasas, Andrea; Béni, Zoltán; Forgo, Peter; Binder, Markus; Bochkov, Valery; Zupkó, István; Krupitza, Georg; Frisch, Richard; Kopp, Brigitte; Hohmann, Judit

2014-03-28

Five new sesquiterpenes, neurolobatin A (1), neurolobatin B (2), 5β-hydroxy-8β-isovaleroyloxy-9α-hydroxycalyculatolide (3), 3-epi-desacetylisovaleroylheliangine (4), and 3β-acetoxy-8β-isovaleroyloxyreynosin (5), were isolated from the aerial parts of Neurolaena lobata. The structures were established by means of a combined spectroscopic data analysis, including ESIMS, APCI-MS, and 1D- and 2D-NMR techniques. Neurolobatin A (1) and B (2) are unusual isomeric seco-germacranolide sesquiterpenes with a bicyclic acetal moiety, compounds 3 and 4 are unsaturated epoxy-germacranolide esters, and compound 5 is the first eudesmanolide isolated from the genus Neurolaena. The isolated compounds (1-5) were shown to have noteworthy antiproliferative activities against human tumor cell lines (A2780, A431, HeLa, and MCF7). The anti-inflammatory effects of 1-5, evaluated in vitro using LPS- and TNF-α-induced IL-8 expression inhibitory assays, revealed that all these compounds strongly down-regulated the LPS-induced production of IL-8 protein, with neurolobatin B (2) and 3-epi-desacetylisovaleroylheliangine (4) being the most effective.

Sesquiterpenes from Neurolaena lobata and Their Antiproliferative and Anti-inflammatory Activities

PubMed Central

2014-01-01

Five new sesquiterpenes, neurolobatin A (1), neurolobatin B (2), 5β-hydroxy-8β-isovaleroyloxy-9α-hydroxycalyculatolide (3), 3-epi-desacetylisovaleroylheliangine (4), and 3β-acetoxy-8β-isovaleroyloxyreynosin (5), were isolated from the aerial parts of Neurolaena lobata. The structures were established by means of a combined spectroscopic data analysis, including ESIMS, APCI-MS, and 1D- and 2D-NMR techniques. Neurolobatin A (1) and B (2) are unusual isomeric seco-germacranolide sesquiterpenes with a bicyclic acetal moiety, compounds 3 and 4 are unsaturated epoxy-germacranolide esters, and compound 5 is the first eudesmanolide isolated from the genus Neurolaena. The isolated compounds (1–5) were shown to have noteworthy antiproliferative activities against human tumor cell lines (A2780, A431, HeLa, and MCF7). The anti-inflammatory effects of 1–5, evaluated in vitro using LPS- and TNF-α-induced IL-8 expression inhibitory assays, revealed that all these compounds strongly down-regulated the LPS-induced production of IL-8 protein, with neurolobatin B (2) and 3-epi-desacetylisovaleroylheliangine (4) being the most effective. PMID:24476550

Serotonergic activity-guided phytochemical investigation of the roots of Angelica sinensis.

PubMed

Deng, Shixin; Chen, Shao-Nong; Yao, Ping; Nikolic, Dejan; van Breemen, Richard B; Bolton, Judy L; Fong, Harry H S; Farnsworth, Norman R; Pauli, Guido F

2006-04-01

Serotonin receptor (5-HT(7)) binding assay-directed fractionation of a methanol extract of the dried roots of Angelica sinensis led to the isolation and identification of 21 compounds including a new phenolic ester, angeliferulate (1), and three new phthalides, 10-angeloylbutylphthalide (2), sinaspirolide (3), and ansaspirolide (4), along with 17 known compounds, p-hydroxyphenethyl trans-ferulate (5), Z-ligustilide (6), Z-butylidenephthalide (7), senkyunolide I (8), Z-6-hydroxy-7-methoxydihydroligustilide (9), N-butylbenzenesulfonamide (10), 11(S),16(R)-dihydroxyoctadeca-9Z,17-diene-12,14-diyn-1-yl acetate (11), (3R,8S)-falcarindiol (12), heptadeca-1-en-9,10-epoxy-4,6-diyne-3,8-diol (13), oplopandiol (14), 8-hydroxy-1-methoxy-, Z-9-heptadecene-4,6-diyn-3-one (15), imperatorin, ferulic acid, vanillin, stigmasterol, sucrose, and 1,3-dilinolenin. This is the first report of a sulfonamide (10) identified from a higher plant source, although its presence needs further investigation. Biosynthetic pathways for dimeric phthalides 3 and 4 are proposed. Compounds 5, 7, 11, 12, 15, and imperatorin exhibited affinity toward 5-HT(7) receptors in a competitive binding assay.

Anticorrosion Properties of Pigments based on Ferrite Coated Zinc Particles

NASA Astrophysics Data System (ADS)

Benda, P.; Kalendová, A.

The paper deals with a new anticorrosion pigment, synthesized on a core-shell basis. For its syntheses a starting substance is used that forms the lamellar shaped core; namely lamellar zinc. The cover of the core is represented by zinc oxide, which is in fact partly oxidized lamellar zinc core, and is created during the calcination of the pigment. The compound that forms the top layer of the core, a ferrite, is also formed during calcination. The formula for the prepared pigment is then defined as MexZn1-xFe2O4/Zn and the formula of thin ferrite layer is MexZn1-xFe2O4 (where Me = Ca, Mg). Due to its shape, this anticorrosion pigment includes another anticorrosion effect, the so called "barrier effect". The mechanisms of anticorrosion effect, corrosion efficiency and mechanical properties were investigated for epoxy-ester paint systems with 10%pigment volume concentration (PVC). Mechanical tests were performed to determine the adhesiveness and mechanical resistance of paints and accelerated corrosion tests were carried out to evaluate efficiency against chemical degradation factors.

40 CFR 721.10209 - Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Epoxy terminated, hydrolyzed... Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin (generic... identified generically as epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol...

40 CFR 721.10209 - Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Epoxy terminated, hydrolyzed... Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin (generic... identified generically as epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol...

40 CFR 721.320 - Acrylamide-substituted epoxy.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Acrylamide-substituted epoxy. 721.320... Substances § 721.320 Acrylamide-substituted epoxy. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as acrylamide-substituted epoxy (PMN P-92-660...

40 CFR 721.320 - Acrylamide-substituted epoxy.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Acrylamide-substituted epoxy. 721.320... Substances § 721.320 Acrylamide-substituted epoxy. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as acrylamide-substituted epoxy (PMN P-92-660...

40 CFR 721.320 - Acrylamide-substituted epoxy.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Acrylamide-substituted epoxy. 721.320... Substances § 721.320 Acrylamide-substituted epoxy. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as acrylamide-substituted epoxy (PMN P-92-660...

40 CFR 721.320 - Acrylamide-substituted epoxy.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Acrylamide-substituted epoxy. 721.320... Substances § 721.320 Acrylamide-substituted epoxy. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as acrylamide-substituted epoxy (PMN P-92-660...

40 CFR 721.320 - Acrylamide-substituted epoxy.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Acrylamide-substituted epoxy. 721.320... Substances § 721.320 Acrylamide-substituted epoxy. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as acrylamide-substituted epoxy (PMN P-92-660...

40 CFR 721.10209 - Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Epoxy terminated, hydrolyzed... Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin (generic... identified generically as epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol...

40 CFR 721.10209 - Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Epoxy terminated, hydrolyzed... Epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol-formaldehyde resin (generic... identified generically as epoxy terminated, hydrolyzed trialkoxysilane and glycidyl ether of phenol...

Mechanical testing of a steel-reinforced epoxy resin bar and clamp for external skeletal fixation of long-bone fractures in cats.

PubMed

Leitch, B J; Worth, A J

2018-05-01

To provide veterinarians with confidence when using a commercially available epoxy resin in external skeletal fixators (ESF), testing was conducted to determine exothermia during curing of the epoxy resin compared to polymethylmethacrylate (PMMA), the hardness of the epoxy resin as a bar over 16 weeks, and the strength of the epoxy resin bar compared with metal clamps in similarly constructed Type 1a ESF constructs simulating the repair of feline long bone fractures. Exothermia of the epoxy resin during curing was tested against PMMA with surface temperatures recorded over the first 15 minutes of curing, using four samples of each product. The hardness of 90 identical epoxy resin bars was tested by subjecting them to cyclic loads (1,000 cycles of 20.5 N, every 7 days) over a 16-week period and impact testing 10 bars every 2 weeks. Ten bars that were not subjected to cyclic loads were impact tested at 0 weeks and another 10 at 16 weeks. Strength of the epoxy resin product, as a bar and clamp composite, was tested against metal SK and Kirschner-Ehmer (KE) clamps and bars in Type 1a, tied-in intramedullary pin, ESF constructs with either 90° or 75° pin placement, subjected to compressive and bending loads to 75 N. The maximum temperature during curing of the epoxy resin (min 39.8, max 43.0)°C was less than the PMMA (min 85.2, max 98.5)°C (p<0.001). There was no change in hardness of the epoxy resin bars over the 16 weeks of cyclic loading (p=0.58). There were no differences between the median strength of the epoxy resin, SK or KE ESF constructs in compression or bending when tested to 75 N (p>0.05). Stiffness of constructs with 75° pin placement was greater for SK than epoxy resin constructs in compression (p=0.046), and was greater for KE than epoxy resin constructs in bending (p=0.033). The epoxy resin tested was found to be less exothermic than PMMA; bars made from the epoxy resin showed durability over an expected fracture healing timeframe and had mechanical strength characteristics comparable to metal bar and clamp ESF constructs. The epoxy resin ESF construct tested in this study can be considered a suitable replacement for SK or KE ESF constructs in the treatment of feline long-bone fractures, in terms of mechanical strength.

Effect on mechanical properties of glass reinforced epoxy (GRE) pipe filled with different geopolymer filler molarity for piping application

NASA Astrophysics Data System (ADS)

Hashim, M. F. Abu; Abdullah, M. M. A.; Ghazali, C. M. R.; Hussin, K.; Binhussain, M.

2017-04-01

This study investigated the use of a novel white clay geopolymer as a filler to produce high strength glass reinforced epoxy pipe. It was found that using white clay geopolymer as filler gives better compressive strength to the glass reinforced epoxy pipe. The disadvantages of current glass reinforced epoxy pipes such low compressive strength which can be replaced by the composite pipes. Geopolymerization is an innovative technology that can transform several aluminosilicate materials into useful products called geopolymers or inorganic polymers. A series of glass reinforced epoxy pipe and glass reinforced epoxy pipe filled with 10 - 40 weight percentages white clay geopolymer filler with 4 Molarity and 8 Molarity were prepared. Morphology of white clay geopolymer filler surface was indicates using scanning electron microscopy. The additions of white clay geopolymer filler for both 4 Molarity and 8 Molarity show higher compressive strength than glass reinforced epoxy pipe without any geopolymer filler. The compressive test of these epoxy geopolymer pipe samples was determined using Instron Universal Testing under compression mode. Nonetheless, the compressive strength of glass reinforced epoxy pipe with white clay geopolymer filler continues to drop when added to 40 wt% of the geopolymer filler loading for both 4 Molarity and 8 Molarity. These outcomes showed that the mixing of geopolymer materials in epoxy system can be attained in this research.

Effect of electron beam irradiation on thermal and mechanical properties of epoxy polymer

NASA Astrophysics Data System (ADS)

Nguyen, A. T.; Visakh, P. M.; Nazarenko, O. B.; Chandran, C. S.; Melnikova, T. V.

2017-01-01

This study investigates the thermal and mechanical properties of epoxy polymer after exposure to different doses of electron beam irradiation. The epoxy polymer was prepared using epoxy-diane resin ED-20 cured by polyethylenepolyamine. The irradiation of the samples was carried out with doses of 30, 100 and 300 kGy. The effects of doses on thermal and mechanical properties of the epoxy polymer were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The thermal properties of the epoxy polymer slightly increased after irradiation at the heating in air. The tensile strength and Young’s modulus of the epoxy polymer increased by the action of electron beam up to dose of 100 kGy and then decreased. The elongation at break decreased with increasing the irradiation dose.

Fracture behavior of nano-scale rubber-modified epoxies

NASA Astrophysics Data System (ADS)

Bacigalupo, Lauren N.

The primary focus of the first portion of this study is to compare physical and mechanical properties of a model epoxy that has been toughened with one of three different types of rubber-based modifier: a traditional telechelic oligomer (phase separates into micro-size particles), a core-shell latex particle (preformed nano-scale particles) and a triblock copolymer (self-assembles into nano-scale particles). The effect of modifier content on the physical properties of the matrix was determined using several thermal analysis methods, which provided insight into any inherent alterations of the epoxy matrix. Although the primary objective is to study the role of particle size on the fracture toughness, stiffness and strength were also determined since these properties are often reduced in rubber-toughened epoxies. It was found that since the CSR- and SBM-modified epoxies are composed of less rubber, thermal and mechanical properties of the epoxy were better maintained. In order to better understand the fracture behavior and mechanisms of the three types of rubber particles utilized in this study, extensive microscopy analysis was conducted. Scanning transmission electron microscopy (STEM) was used to quantify the volume fraction of particles, transmission optical microscopy (TOM) was used to determine plastic damage zone size, and scanning electron microscopy (SEM) was used to assess void growth in the plastic zone after fracture. By quantifying these characteristics, it was then possible to model the plastic damage zone size as well as the fracture toughness to elucidate the behavior of the rubber-modified epoxies. It was found that localized shear yielding and matrix void growth are the active toughening mechanisms in all rubber-modified epoxies in this study, however, matrix void growth was more prevalent. The second portion of this study investigated the use of three acrylate-based triblocks and four acrylate-based diblocks to modify a model epoxy system. By varying block lengths and the polarity of the epoxy-miscible blocks, a variety of morphologies were generated (such as spherical micelles, layer particles and worm-like micelles). It was found that in some cases, the epoxy-miscible block did not yield domains substantial enough to facilitate increases in toughness. Overall, the thermal and mechanical properties of the acrylate-based triblock- and diblock-modified epoxies were found to be similar to CTBN-modified epoxy, which was used as a control. However, there were properties that were improved with the acrylate-based diblock-modified epoxies when compared to the acrylate-based triblock modified epoxies. Specifically, the viscosity penalty of the diblock-modified epoxies was shown to be a marked improvement over the triblock-modified epoxies, especially given that the fracture toughness values are similar. This reduction in the viscosity penalty becomes an important criterion when considering processing procedures and applications. Additionally, comparing the morphology of the resulting modified-epoxies utilizing atomic force microscopy (AFM) and scanning electron microscopy (SEM) led to a better understanding of the relationship between the particle morphology obtained and the physical properties of the acrylate-based rubber-modified epoxy systems in this research.

21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

Code of Federal Regulations, 2014 CFR

2014-04-01

...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION...,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The resins identified in paragraph (a) of... condensation of xylene-formaldehyde resin and 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins, to...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.1850 - Toluene sulfonamide bis-phe-nol A epoxy adduct.

Code of Federal Regulations, 2014 CFR

2014-07-01

... epoxy adduct. 721.1850 Section 721.1850 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1850 Toluene sulfonamide bis-phe-nol A epoxy adduct. (a) Chemical... as toluene sulfonamide bisphenol A epoxy adduct (PMN P-90-113) is subject to reporting under this...

40 CFR 721.1850 - Toluene sulfonamide bis-phe-nol A epoxy adduct.

Code of Federal Regulations, 2012 CFR

2012-07-01

... epoxy adduct. 721.1850 Section 721.1850 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1850 Toluene sulfonamide bis-phe-nol A epoxy adduct. (a) Chemical... as toluene sulfonamide bisphenol A epoxy adduct (PMN P-90-113) is subject to reporting under this...

40 CFR 721.2752 - Epoxy resin containing phosphorus (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Epoxy resin containing phosphorus... Specific Chemical Substances § 721.2752 Epoxy resin containing phosphorus (generic). (a) Chemical substance... epoxy resin containing phosphorus (PMN P-00-912) is subject to reporting under this section for the...

40 CFR 721.10113 - Thioether epoxy (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Thioether epoxy (generic). 721.10113... Substances § 721.10113 Thioether epoxy (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as thioether epoxy (PMN P-04-547) is subject to...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.1850 - Toluene sulfonamide bis-phe-nol A epoxy adduct.

Code of Federal Regulations, 2013 CFR

2013-07-01

... epoxy adduct. 721.1850 Section 721.1850 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1850 Toluene sulfonamide bis-phe-nol A epoxy adduct. (a) Chemical... as toluene sulfonamide bisphenol A epoxy adduct (PMN P-90-113) is subject to reporting under this...

40 CFR 721.10113 - Thioether epoxy (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Thioether epoxy (generic). 721.10113... Substances § 721.10113 Thioether epoxy (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as thioether epoxy (PMN P-04-547) is subject to...

40 CFR 721.10113 - Thioether epoxy (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Thioether epoxy (generic). 721.10113... Substances § 721.10113 Thioether epoxy (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as thioether epoxy (PMN P-04-547) is subject to...

40 CFR 721.10113 - Thioether epoxy (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Thioether epoxy (generic). 721.10113... Substances § 721.10113 Thioether epoxy (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as thioether epoxy (PMN P-04-547) is subject to...

40 CFR 721.10603 - Epoxy modified alkyd resin, partially neutralized (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Epoxy modified alkyd resin, partially... Specific Chemical Substances § 721.10603 Epoxy modified alkyd resin, partially neutralized (generic). (a... generically as epoxy modified alkyd resin, partially neutralized (PMN P-11-280) is subject to reporting under...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.10113 - Thioether epoxy (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Thioether epoxy (generic). 721.10113... Substances § 721.10113 Thioether epoxy (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as thioether epoxy (PMN P-04-547) is subject to...

40 CFR 721.1850 - Toluene sulfonamide bis-phe-nol A epoxy adduct.

Code of Federal Regulations, 2011 CFR

2011-07-01

... epoxy adduct. 721.1850 Section 721.1850 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1850 Toluene sulfonamide bis-phe-nol A epoxy adduct. (a) Chemical... as toluene sulfonamide bisphenol A epoxy adduct (PMN P-90-113) is subject to reporting under this...

40 CFR 721.2752 - Epoxy resin containing phosphorus (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Epoxy resin containing phosphorus... Specific Chemical Substances § 721.2752 Epoxy resin containing phosphorus (generic). (a) Chemical substance... epoxy resin containing phosphorus (PMN P-00-912) is subject to reporting under this section for the...

40 CFR 721.2752 - Epoxy resin containing phosphorus (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Epoxy resin containing phosphorus... Specific Chemical Substances § 721.2752 Epoxy resin containing phosphorus (generic). (a) Chemical substance... epoxy resin containing phosphorus (PMN P-00-912) is subject to reporting under this section for the...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.10603 - Epoxy modified alkyd resin, partially neutralized (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Epoxy modified alkyd resin, partially... Specific Chemical Substances § 721.10603 Epoxy modified alkyd resin, partially neutralized (generic). (a... generically as epoxy modified alkyd resin, partially neutralized (PMN P-11-280) is subject to reporting under...

40 CFR 721.2752 - Epoxy resin containing phosphorus (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Epoxy resin containing phosphorus... Specific Chemical Substances § 721.2752 Epoxy resin containing phosphorus (generic). (a) Chemical substance... epoxy resin containing phosphorus (PMN P-00-912) is subject to reporting under this section for the...

40 CFR 721.2752 - Epoxy resin containing phosphorus (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Epoxy resin containing phosphorus... Specific Chemical Substances § 721.2752 Epoxy resin containing phosphorus (generic). (a) Chemical substance... epoxy resin containing phosphorus (PMN P-00-912) is subject to reporting under this section for the...

Chromium Ions Improve Moisure Resistance of Epoxy Resins

NASA Technical Reports Server (NTRS)

St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

1986-01-01

Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

Synthesis and Structure Property Studies of Toughened Epoxy Resins via Functionalized Polysiloxanes. Friction and Wear Studies.

DTIC Science & Technology

1987-03-30

TFP) siloxane and of ATBN and CTBN rubber modified epoxies were previously reported,,[1]. There was no significant evidence that the low surface energy...siloxane- modified epoxies reduced friction compared with the unmodified epoxy or the ATBN and CTBN modified epoxies. The reduction in wear noted for...is for the control, but their elastic moduli are lower. The CTBN samples from the previous work also had higher wear rates at the 5 percent level. It

Ex situ generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes.

PubMed

Kristensen, Steffan K; Eikeland, Espen Z; Taarning, Esben; Lindhardt, Anders T; Skrydstrup, Troels

2017-12-01

A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of ex situ generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts. Cyanation was achieved employing the Pd(0) precatalyst, P( t Bu) 3 -Pd-G3 and a weak base, potassium acetate, in a dioxane-water solvent mixture. The methodology was also suitable for the synthesis of 13 C-labelled benzonitriles with ex situ generated 13 C-hydrogen cyanide. Stoichiometric studies with the metal complexes were undertaken to delineate the mechanism for this catalytic transformation. Treatment of Pd(P( t Bu) 3 ) 2 with H 13 CN in THF provided two Pd-hydride complexes, (P( t Bu) 3 ) 2 Pd(H)( 13 CN), and [(P( t Bu) 3 )Pd(H)] 2 Pd( 13 CN) 4 , both of which were isolated and characterised by NMR spectroscopy and X-ray crystal structure analysis. When the same reaction was performed in a THF : water mixture in the presence of KOAc, only (P( t Bu) 3 ) 2 Pd(H)( 13 CN) was formed. Subjection of this cyano hydride metal complex with the oxidative addition complex (P( t Bu) 3 )Pd(Ph)(Br) in a 1 : 1 ratio in THF led to a transmetallation step with the formation of (P( t Bu) 3 ) 2 Pd(H)(Br) and 13 C-benzonitrile from a reductive elimination step. These experiments suggest the possibility of a catalytic cycle involving initially the formation of two Pd(ii)-species from the oxidative addition of L n Pd(0) into HCN and an aryl bromide followed by a transmetallation step to L n Pd(Ar)(CN) and L n Pd(H)(Br), which both reductively eliminate, the latter in the presence of KOAc, to generate the benzonitrile and L n Pd(0).

Effect of nanoparticles dispersion on viscoelastic properties of epoxy-zirconia polymer nanocomposites

NASA Astrophysics Data System (ADS)

Singh, Sushil Kumar; Kumar, Abhishek; Jain, Anuj

2018-03-01

In the present work zirconia-nanoparticles were dispersed in epoxy matrix to form epoxy-zirconia polymer nanocomposites using ultrasonication and viscoelastic properties of nanocomposites were investigated. For the same spherical zirconia-nanoparticles (45 nm) were dispersed in weight fraction of 2, 4, 6 and 8 % to reinforce the epoxy. DMA results show the significant enhancement in viscoelastic properties with the dispersion of zirconia nanoparticles in the epoxy matrix. The value of storage modulus and glass transition temperature increases from 179 MPa (pristine) to 225 MPa (6 wt.% ZrO2) and 61 °C (pristine) to 70 °C (6 wt.% ZrO2) respectively with the dispersion of zirconia nanoparticles in the epoxy.

Technology of civil usage of composites. [in commercial aircraft structures

NASA Technical Reports Server (NTRS)

Kemp, D. E.

1977-01-01

The paper deals with the use of advanced composites in structural components of commercial aircraft. The need for testing the response of a material system to service environment is discussed along with methods for evaluating design and manufacturing aspects of a built-up structure under environmental conditions and fail-safe (damage-tolerance) evaluation of structures. Crashworthiness aspects, the fire-hazard potential, and electrical damage of composite structures are considered. Practical operational experience with commercial aircraft is reviewed for boron/epoxy foreflaps, Kevlar/epoxy fillets and fairings, graphite/epoxy spoilers, graphite/polysulfone spoilers, graphite/epoxy floor posts, boron/aluminum aft pylon skin panels, graphite/epoxy engine nose cowl outer barrels, and graphite/epoxy upper aft rudder segments.

Adhesion at the interface in cured graphite fiber epoxy-amine resin composites

NASA Technical Reports Server (NTRS)

Needles, Howard L.; Alger, Kenneth W.; Okamoto, Robert

1987-01-01

The effect of high temperature curing on the interface between unsized or epoxy-sized graphite fiber tow and epoxy-amine resin was examined by scanning electron microscopy of compression and freeze fractured specimens. Little or no adhesion was found between the unsized graphite fiber tows and the epoxy-amine resin on curing at 165 C for 17 hrs. Epoxy-sized graphite fibers showed a similar lack of adhesion between the fiber tows and the epoxy-amine resin at 3 and 17 hr cures, although good penetration of the resin into the sized fiber tows had occurred. Interfacial bond strengths for the composites could not be effectively measured by compression fracture of specimens.

Epoxy based nanocomposites with fully exfoliated unmodified clay: mechanical and thermal properties.

PubMed

Li, Binghai; Zhang, Xiaohong; Gao, Jianming; Song, Zhihai; Qi, Guicun; Liu, Yiqun; Qiao, Jinliang

2010-09-01

The unmodified clay has been fully exfoliated in epoxy resin with the aid of a novel ultrafine full-vulcanized powdered rubber. Epoxy/rubber/clay nanocomposites with exfoliated morphology have been successfully prepared. The microstructures of the nanocomposites were characterized by means of X-ray diffraction and transmission electron microscopy. It was found that the unmodified clay was fully exfoliated and uniformly dispersed in the resulting nanocomposite. Characterizations of mechanical properties revealed that the impact strength of this special epoxy/rubber/clay nanocomposite increased up 107% over the neat epoxy resin. Thermal analyses showed that thermal stability of the nanocomposite was much better than that of epoxy nanocomposite based on organically modified clay.

A study of the effects of long-term exposure to fuels and fluids on the behavior of advanced composite materials

NASA Technical Reports Server (NTRS)

Tanimoto, E. Y.

1981-01-01

The periodic testing and evaluation of graphite/epoxy and Kevlar/epoxy material systems after subjecting test specimens to prolonged exposure to several laboratory-controlled environments deemed typical of normal aircraft operations is discussed. It is noted that specimen immersion in water or water-based fluids resulted in the greatest effect on the mechanical properties tested. Also, the environmental fluids showed a tendency to affect Kevlar/epoxy systems at an earlier exposure period than the graphite/epoxy systems. Results also indicate mechanical property strength retention generally being lower for the Kevlar/epoxy systems when compared to the corresponding graphite/epoxy systems in similar environments, after prolonged exposure.

Mechanical and thermal properties of MoS2 reinforced epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Madeshwaran, S. R.; Jayaganthan, R.; Velmurugan, R.; Gupta, N. K.; Manzhirov, A. V.

2018-04-01

The effects of molybdenum disulfide (MoS2) on thermal expansion and mechanical properties of epoxy composites were investigated. MoS2 nanosheets were exfoliated by ultra-sonication and reinforced into epoxy as nanofiller by mechanical stirring. Transmission electron microscopy observations demonstrated that MoS2 exhibited better dispersion in epoxy matrix. Thermal expansion measured by dilatometer has revealed that increasing MoS2 fractioninepoxy matrix significantly reduced the coefficient of thermal expansion (CTE). The 0.5wt% MoS2 incorporated epoxy composites shows 35.8% reduction in CTE as compared to neat epoxy. The addition of small fraction of MoS2(0.1wt%) in the composites increased the tensile and flexural strength 39.2% and 9.0% respectively. The glass transition temperature (Tg ) of 0.1wt% MoS2 incorporated epoxy composites shows 7.39% increase in Tg .

Enhancing Mechanical and Thermal Properties of Epoxy Nanocomposites via Alignment of Magnetized SiC Whiskers.

PubMed

Townsend, James; Burtovyy, Ruslan; Aprelev, Pavel; Kornev, Konstantin G; Luzinov, Igor

2017-07-12

This research is focused on the fabrication and properties of epoxy nanocomposites containing magnetized SiC whiskers (MSiCWs). To this end, we report an original strategy for fabrication of magnetically active SiCWs by decorating the whiskers with magnetic (iron oxide) nanoparticles via polymer-polymer (poly(acrylic acid)/poly(2-vinyl pyridine)) complexation. The obtained whiskers demonstrated a substantial magnetic response in the polymerizing epoxy resin, with application of only a 20 mT (200 G) magnetic field. We also found that the whiskers chemically reacted with the epoxy resin, causing formation of an extended interphase near the boundary of the whiskers. The SiC whiskers oriented with the magnetic field demonstrated positive effects on the behavior of epoxy-based nanocomposites. Namely, the aligned MSiCWs enhanced the thermomechanical properties of the materials significantly above that of the neat epoxy and epoxy nanocomposite, with randomly oriented whiskers.

High performance UV and thermal cure hybrid epoxy adhesive

NASA Astrophysics Data System (ADS)

Chen, C. F.; Iwasaki, S.; Kanari, M.; Li, B.; Wang, C.; Lu, D. Q.

2017-06-01

New type one component UV and thermal curable hybrid epoxy adhesive was successfully developed. The hybrid epoxy adhesive is complete initiator free composition. Neither photo-initiator nor thermal initiator is contained. The hybrid adhesive is mainly composed of special designed liquid bismaleimide, partially acrylated epoxy resin, acrylic monomer, epoxy resin and latent curing agent. Its UV light and thermal cure behavior was studied by FT-IR spectroscopy and FT-Raman spectroscopy. Adhesive samples cured at UV only, thermal only and UV + thermal cure conditions were investigated. By calculated conversion rate of double bond in both acrylic component and maleimide compound, satisfactory light curability of the hybrid epoxy adhesive was confirmed quantitatively. The investigation results also showed that its UV cure components, acrylic and bismalimide, possess good thermal curability too. The initiator free hybrid epoxy adhesive showed satisfactory UV curability, good thermal curability and high adhesion performance.

Physical aging and its influence on the reliability of network epoxies and epoxy-matrix composites

NASA Technical Reports Server (NTRS)

Heinemann, K.

1983-01-01

The matrix-dominated physical and mechanical properties of a carbon fiber reinforced epoxy composite and a neat epoxy resin were found to be affected by sub-Tg annealing in nitrogen and dark atmosphere. Postcured specimens of Thornel 300 carbon-fiber/Fiberite 934 epoxy as well as Fiberite 934 epoxy resin were quenched from above Tg and given annealing at 140 C, 110 C, or 80 C, for time up to one-hundred thousand minutes. No weight loss was observed during annealing at these temperatures. Significant variations were found in density, modulus, hardness, damping, moisture absorption ability, thermal expansivity. Moisture-epoxy interactious were also studied. The kinetics of aging as well as the molecular aggregation during this densification process were monitored by differential scanning calorimetry, dynamic mechanical analysis, density gradient column, microhardness tester, Instron, and solid-state nuclear magnetic resonance spectroscopy.

[The research of biodegradation of a composite material used in reconstructive and reparative surgery of maxillofacial area].

PubMed

Malanchuk, V O; Astapenko, O O; Halatenko, N A; Rozhnova, R A

2013-09-01

Dates about the research of biodegradation of epoxy-polyurethane composite material used in reconstructive and reparative surgery of maxillofacial area are reflected in the article. Was founded: 1) notable biodegradation of species from epoxy-polyurethane composition in the term of observation up to 6 months was not founded. That testifies their preservation of physical and mechanical properties. 2) founded, that in species from epoxy-polyurethane composition, which contain levamisole, processes of biodegradation are faster then in species from pure epoxy-polyurethane composition and in species from epoxy-polyurethane composition with hydroxyapatite; 3) material from epoxy-polyurethane composition, which contains levamisole and hydroxyapatite, stays in biological environment in small quantity of petty fragments during the incubation in term of 2 years. So, it biodegrades practically totally. Authors suggest on the basis of achieved information, that the use of epoxy-polyurethane constructions that biodegrade, is pertinently in reconstructive maxillofacial surgery.

21 CFR 177.2280 - 4,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins.

Code of Federal Regulations, 2013 CFR

2013-04-01

... thermo-setting epoxy resins. 177.2280 Section 177.2280 Food and Drugs FOOD AND DRUG ADMINISTRATION...,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins. 4,4′-Isopropylidenediphenol-epichlo-rohydrin thermosetting epoxy resins may be safely used as articles or components of...

21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

Code of Federal Regulations, 2010 CFR

2010-04-01

...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant substances...

21 CFR 177.2280 - 4,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins.

Code of Federal Regulations, 2012 CFR

2012-04-01

... thermo-setting epoxy resins. 177.2280 Section 177.2280 Food and Drugs FOOD AND DRUG ADMINISTRATION...,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins. 4,4′-Isopropylidenediphenol-epichlo-rohydrin thermosetting epoxy resins may be safely used as articles or components of...

21 CFR 177.2280 - 4,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins.

Code of Federal Regulations, 2014 CFR

2014-04-01

... thermo-setting epoxy resins. 177.2280 Section 177.2280 Food and Drugs FOOD AND DRUG ADMINISTRATION...-epichloro-hydrin thermo-setting epoxy resins. 4,4′-Isopropylidenediphenol-epichlo-rohydrin thermosetting epoxy resins may be safely used as articles or components of articles intended for repeated use in...

21 CFR 177.2280 - 4,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

... thermo-setting epoxy resins. 177.2280 Section 177.2280 Food and Drugs FOOD AND DRUG ADMINISTRATION...,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins. 4,4′-Isopropylidenediphenol-epichlo-rohydrin thermosetting epoxy resins may be safely used as articles or components of...

21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant substances...

21 CFR 177.2280 - 4,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins.

Code of Federal Regulations, 2010 CFR

2010-04-01

... thermo-setting epoxy resins. 177.2280 Section 177.2280 Food and Drugs FOOD AND DRUG ADMINISTRATION...,4′-Isopropyl-idenedi-phenol-epichloro-hydrin thermo-setting epoxy resins. 4,4′-Isopropylidenediphenol-epichlo-rohydrin thermosetting epoxy resins may be safely used as articles or components of...

21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

Code of Federal Regulations, 2012 CFR

2012-04-01

...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant substances...

21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

Code of Federal Regulations, 2013 CFR

2013-04-01

...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant substances...

Heat-Conducting Anchors for Thermocouples

NASA Technical Reports Server (NTRS)

Macdavid, Kenton S.

1987-01-01

Metal particles in adhesive aid heat transfer. Aluminum caps containing silver-filled epoxy used as high-thermal-conductance anchors for thermocouples, epoxy providing thermal path between mounting surfaces and thermocouple measuring junctions. Normally, epoxy-filled aluminum caps used when measuring steady-state temperatures. Silver-filled epoxy used when thermocouple not isolated electrically from surface measured.

Preparation of well-controlled three-dimensional skeletal hybrid monoliths via thiol-epoxy click polymerization for highly efficient separation of small molecules in capillary liquid chromatography.

PubMed

Lin, Hui; Chen, Lianfang; Ou, Junjie; Liu, Zhongshan; Wang, Hongwei; Dong, Jing; Zou, Hanfa

2015-10-16

Two kinds of hybrid monoliths were first prepared via thiol-epoxy click polymerization using a multi-epoxy monomer, octaglycidyldimethylsilyl POSS (POSS-epoxy), and two multi-thiols, trimethylolpropanetris(3-mercaptopropionate) (TPTM) and pentaerythritoltetrakis(3-mercaptopropionate) (PTM), respectively, as the precursors. The resulting two hybrid monoliths (assigned as POSS-epoxy-TPTM and POSS-epoxy-PTM) not only possessed high thermal, mechanical and chemical stabilities, but also exhibited well-controlled 3D skeletal microstructure and high efficiency in capillary liquid chromatography (cLC) separation of small molecules. The highest column efficiency reached 182,700N/m (for butylbenzene) on the monolith POSS-epoxy-PTM at the velocity of 0.75mm/s. Furthermore, the hybrid monolith POSS-epoxy-PTM was successfully applied for cLC separations of various samples, not only standard compounds such as alkylbenzenes, PAHs, phenols and dipeptides, as well as intact proteins, but also complex samples of EPA 610 and BSA digest. Copyright © 2015 Elsevier B.V. All rights reserved.

Carbon nanotube modification using gum arabic and its effect on the dispersion and tensile properties of carbon nanotubes/epoxy nanocomposites.

PubMed

Kim, Man Tae; Park, Ho Seok; Hui, David; Rhee, Kyong Yop

2011-08-01

In this study, the effects of a MWCNT treatment on the dispersion of MWCNTs in aqueous solution and the tensile properties of MWCNT/epoxy nanocomposites were investigated. MWCNTs were treated using acid and gum arabic, and MWCNT/epoxy nanocomposites were fabricated with 0.3 wt.% unmodified, oxidized and gum-treated MWCNTs. The dispersion states of the unmodified, oxidized, and Gum-treated MWCNTs were characterized in distilled water. The tensile strengths and elastic modulus of the three nanocomposites were determined and compared. The results indicated that the gum treatment produced better dispersion of the MWCNTs in distilled water and that gum-treated MWCNT/epoxy nanocomposites had a better tensile strength and elastic modulus than did the unmodified and acid-treated MWCNT/epoxy nanocomposites. Scanning electron microscope examination of the fracture surface showed that the improved tensile properties of the gum-treated MWCNT/epoxy nanocomposites were attributed to the improved dispersion of MWCNTs in the epoxy and to interfacial bonding between nanotubes and the epoxy matrix.

Incorporation of Fe3O4/CNTs nanocomposite in an epoxy coating for corrosion protection of carbon steel

NASA Astrophysics Data System (ADS)

Pham, Gia Vu; Truc Trinh, Anh; To, Thi Xuan Hang; Duong Nguyen, Thuy; Trang Nguyen, Thu; Hoan Nguyen, Xuan

2014-09-01

In this study Fe3O4/CNTs composite with magnetic property was prepared by attaching magnetic nanoparticles (Fe3O4) to carbon nanotubes (CNTs) by hydrothermal method. The obtained Fe3O4/CNTs composite was characterized by Fourier transform infrared (FTIR) spectroscopy, powder x-ray diffraction and transmission electron microscopy. The Fe3O4/CNTs composite was then incorporated into an epoxy coating at concentration of 3 wt%. Corrosion protection of epoxy coating containing Fe3O4/CNTs composite was evaluated by electrochemical impedance spectroscopy and adhesion measurement. The impedance measurements show that Fe3O4/CNTs composite enhanced the corrosion protection of epoxy coating. The corrosion resistance of the carbon steel coated by epoxy coating containing Fe3O4/CNTs composite was significantly higher than that of carbon steel coated by clear epoxy coating and epoxy coating containing CNTs. FE-SEM photographs of fracture surface of coatings showed good dispersion of Fe3O4/CNTs composite in the epoxy matrix.

Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids

PubMed Central

Yang, Cheng-Fu; Wang, Li-Fen; Wu, Song-Mao; Su, Chean-Cheng

2015-01-01

The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC), 29Si nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). To improve the compatibility between the organic and inorganic phases, a coupling agent was used to modify the diglycidyl ether of bisphenol A (DGEBA) epoxy. The sol-gel technique enables the silica to be successfully incorporated into the network of the hybrids, increasing the thermal stability and improving the mechanical properties of the prepared epoxy/silica nano-hybrids. An autocatalytic mechanism of the epoxy/SiO2 nanocomposites was observed. The low reaction rate of epoxy in the nanocomposites is caused by the steric hindrance in the network of hybrids that arises from the consuming of epoxide group in the network of hybrids by the silica. In the nanocomposites, the nano-scale silica particles had an average size of approximately 35 nm, and the particles were well dispersed in the epoxy matrix, according to the TEM images. PMID:28793616

Improvement of Mechanical and Dielectric Properties of Epoxy Resin Using CNTs/ZnO Nanocomposite.

PubMed

Vu, Pham Gia; Truc, Trinh Anh; Chinh, Nguyen Thuy; Tham, Do Quang; Trung, Tran Huu; Oanh, Vu Ke; Hang, To Thi Xuan; Olivier, Marjorie; Hoang, Thai

2018-04-01

In this study, carbon nanotubes (CNTs)/ZnO composites had been prepared using the sol-gel method and then incorporated into an epoxy resin for reinforcement of mechanical and electrical properties. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD) Field Emission Scanning Electron Microscope (FE-SEM) analyses show that the ZnO nanoparticles deposited on CNTs were crystallized in a hexagonal wurtzite structure. Average particle size of ZnO deposited on the CNT was about 8 nm. The mechanical and dielectric properties of epoxy containing CNTs/ZnO were investigated in comparison to epoxy resin and epoxy resin containing only CNT or ZnO nanoparticles. The results indicated that tensile strength and elongation at break of the nanocomposite were substantially improved with the presence of CNTs/ZnO at the equal volume. The DSC analysis associate with the dielectric results shows that the behavior of epoxy/CNTs/ZnO is identical to epoxy/ZnO composite, and the CNTs is essential to the distributed arrangement of ZnO in the epoxy resin.

Ultrasound aided smooth dispensing for high viscoelastic epoxy in microelectronic packaging.

PubMed

Chen, Yun; Li, Han-Xiong; Shan, Xiuyang; Gao, Jian; Chen, Xin; Wang, Fuliang

2016-01-01

Epoxy dispensing is one of the most critical processes in microelectronic packaging. However, due its high viscoelasticity, dispensing of epoxy is extremely difficult, and a lower viscoelasticity epoxy is desired to improve the process. In this paper, a novel method is proposed to achieve a lowered viscoelastic epoxy by using ultrasound. The viscoelasticity and molecular structures of the epoxies were compared and analyzed before and after experimentation. Different factors of the ultrasonic process, including power, processing time and ultrasonic energy, were studied in this study. It is found that elasticity is more sensitive to ultrasonic processing while viscosity is little affected. Further, large power and long processing time can minimize the viscoelasticity to ideal values. Due to the reduced loss modulus and storage modulus after ultrasonic processing, smooth dispensing is demonstrated for the processed epoxy. The subsequently color temperature experiments show that ultrasonic processing will not affect LED's lighting. It is clear that the ultrasonic processing will have good potential to aide smooth dispensing for high viscoelastic epoxy in electronic industry. Copyright © 2015 Elsevier B.V. All rights reserved.

Imide modified epoxy matrix resins

NASA Technical Reports Server (NTRS)

Scola, D. A.; Pater, R. H.

1981-01-01

High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.

Performance of 2G-HTS REBCO undulator coils impregnated epoxies mixed with different fillers

DOE PAGES

Kesgin, Ibrahim; Hasse, Quentin; Ivanyushenkov, Yury; ...

2016-12-12

The use of second-generation high-temperature superconducting-coated conductors enables an enhancement of the performance of undulator magnets. However, preventing the motion of the wire and providing sufficient conduction cooling to the winding stacks have remained challenges. In this study, we have evaluated epoxy impregnation techniques to address these issues. Epoxy resin was prepared with different nanopowders and the effect on the performance of the undulator coil pack was investigated. All epoxy impregnated coils showed smaller n values and some degree of deterioration of the critical current I c. The I c degradation was most pronounced for epoxy mixed with high aspectmore » ratio multiwalled carbon nanotubes (MWCNTs). It has been found that the crack formation in the epoxy results in plastic deformation of the copper stabilizer layer, which causes the underlying ceramic REBCO superconducting layer to crack resulting in degradation of the superconducting tape performance. As a result, careful adjustment of epoxy thickness surrounding the superconductor and the powder ratio in the epoxy eliminate the performance degradation.« less

Thermal properties of oil palm nano filler/kenaf reinforced epoxy hybrid nanocomposites

NASA Astrophysics Data System (ADS)

Saba, N.; Paridah, M. T.; Abdan, K.; Ibrahim, N. A.

2016-11-01

The aim of this research study was to fabricate nano oil palm empty fruit bunch (OPEFB)/kenaf/epoxy hybrid nanocomposites and to make comparative study on the thermal properties of nano OPEFB/kenaf/epoxy hybrid nanocomposites with the montmorillonite (MMT)/kenaf/epoxy hybrid nanocomposites and organically modified MMT (OMMT)/kenaf/epoxy hybrid nanocomposites. Epoxy based kenaf hybrid nanocomposites was prepared by dispersing the nano filler (nano OPEFB filler, MMT, OMMT) at 3% loading through high speed mechanical stirrer followed by hand lay-up technique. Thermal properties of hybrid nanocomposites were analyzed through thermogravimetry analyzer (TGA), and differential scanning calorimetry (DSC). Obtained results specified that addition of nano OPEFB filler improves the thermal stability and char yield of kenaf/epoxy composites. Furthermore, the increase in decomposition temperature by the nano OPEFB filler was quite comparable to the MMT/kenaf/epoxy but relatively less than OMMT/kenaf/epoxy hybrid nanocomposites. We concluded from overall consequences that the nano OPEFB filler can be used as the promising and innovative alternative of existing expensive nano filler, with relatively lesser impact on the environment having marked pronounced impact on the construction, automotive, aerospace, electronics and semiconducting sectors as future industries based on bio-wastes with satisfactory light weight and thermal stability on other side.

Preparation and optical properties of indium tin oxide/epoxy nanocomposites with polyglycidyl methacrylate grafted nanoparticles.

PubMed

Tao, Peng; Viswanath, Anand; Schadler, Linda S; Benicewicz, Brian C; Siegel, Richard W

2011-09-01

Visibly highly transparent indium tin oxide (ITO)/epoxy nanocomposites were prepared by dispersing polyglycidyl methacrylate (PGMA) grafted ITO nanoparticles into a commercial epoxy resin. The oleic acid stabilized, highly crystalline, and near monodisperse ITO nanoparticles were synthesized via a nonaqueous synthetic route with multigram batch quantities. An azido-phosphate ligand was synthesized and used to exchange with oleic acid on the ITO surface. The azide terminal group allows for the grafting of epoxy resin compatible PGMA polymer chains via Cu(I) catalyzed alkyne-azide "click" chemistry. Transmission electron microscopy (TEM) observation shows that PGMA grafted ITO particles were homogeneously dispersed within the epoxy matrix. Optical properties of ITO/epoxy nanocomposites with different ITO concentrations were studied with an ultraviolet-visible-near-infrared (UV-vis-NIR) spectrometer. All the ITO/epoxy nanocomposites show more than 90% optical transparency in the visible light range and absorption of UV light from 300 to 400 nm. In the near-infrared region, ITO/epoxy nanocomposites demonstrate low transmittance and the infrared (IR) transmission cutoff wavelength of the composites shifts toward the lower wavelength with increased ITO concentration. The ITO/epoxy nanocomposites were applied onto both glass and plastic substrates as visibly transparent and UV/IR opaque optical coatings.

Fabrication of tough epoxy with shape memory effects by UV-assisted direct-ink write printing.

PubMed

Chen, Kaijuan; Kuang, Xiao; Li, Vincent; Kang, Guozheng; Qi, H Jerry

2018-03-07

3D printing of epoxy-based shape memory polymers with high mechanical strength, excellent thermal stability and chemical resistance is highly desirable for practical applications. However, thermally cured epoxy in general is difficult to print directly. There have been limited numbers of successes in printing epoxy but they suffer from relatively poor mechanical properties. Here, we present an ultraviolet (UV)-assisted 3D printing of thermally cured epoxy composites with high tensile toughness via a two-stage curing approach. The ink containing UV curable resin and epoxy oligomer is used for UV-assisted direct-ink write (DIW)-based 3D printing followed by thermal curing of the part containing the epoxy oligomer. The UV curable resin forms a network by photo polymerization after the 1st stage of UV curing, which can maintain the printed architecture at an elevated temperature. The 2nd stage thermal curing of the epoxy oligomer yields an interpenetrating polymer network (IPN) composite with highly enhanced mechanical properties. It is found that the printed IPN epoxy composites enabled by the two-stage curing show isotropic mechanical properties and high tensile toughness. We demonstrated that the 3D-printed high-toughness epoxy composites show good shape memory properties. This UV-assisted DIW 3D printing via a two-stage curing method can broaden the application of 3D printing to fabricate thermoset materials with enhanced tensile toughness and tunable properties for high-performance and functional applications.

Green Preparation of Epoxy/Graphene Oxide Nanocomposites Using a Glycidylamine Epoxy Resin as the Surface Modifier and Phase Transfer Agent of Graphene Oxide.

PubMed

Tang, Xinlei; Zhou, Yang; Peng, Mao

2016-01-27

In studies of epoxy/graphene oxide (GO) nanocomposites, organic solvents are commonly used to disperse GO, and vigorous mechanical processes and complicated modification of GO are usually required, increasing the cost and hindering the development and application of epoxy nanocomposites. Here, we report a green, facile, and efficient method of preparing epoxy/GO nanocomposites. When triglycidyl para-aminophenol (TGPAP), a commercially available glycidyl amine epoxy resin with one tertiary amine group per molecule, is used as both the surface modifier and phase transfer agent of GO, GO can be directly and rapidly transferred from water to diglycidyl ether of bisphenol A and other types of epoxy resins by manual stirring under ambient conditions, whereas GO cannot be transferred to these epoxy resins in the absence of TGPAP. The interaction between TGPAP and GO and the effect of the TGPAP content on the dispersion of GO in the epoxy matrix were investigated systematically. Superior dispersion and exfoliation of GO nanosheets and remarkably improved mechanical properties, including tensile and flexural properties, toughness, storage modulus, and microhardness, of the epoxy/GO nanocomposites with a suitable amount of TGPAP were demonstrated. This method is organic-solvent-free and technically feasible for large-scale preparation of high-performance nanocomposites; it opens up new opportunities for exploiting the unique properties of graphene or even other nanofillers for a wide range of applications.

The effects of MWNT on thermal conductivity and thermal mechanical properties of epoxy

NASA Astrophysics Data System (ADS)

Ismadi, A. I.; Othman, R. N.

2017-12-01

Multiwall nanotube (MWNT) was used as filler in various studies to improve thermal conductivity and mechanical properties of epoxy. Present study varied different weight loading (0, 0.1 %, 0.5 %, 1 %, 1.5 %, 3 % and 5 %) of MWNT in order to observe the effects on the epoxy. Nanocomposite was analyzed by dynamic-mechanical thermal analyser (DMTA) and KD2 pro analyzer. DMTA measured storage modulus (E') and glass transition temperature (Tg) of the nanocomposite. Result showed that Tg value of neat epoxy is higher than all MWNT epoxy nanocomposite. Tg values drop from 81.55 °C (neat epoxy) to 65.03 °C (at 0.1 wt%). This may happen due to the agglomeration of MWNT in the epoxy. However, Tg values increases with the increase of MWNT wt%. Tg values increased from 65.03 °C to 78.53 °C at 1 wt%. Increment of storage modulus (E') at 3 °C (glassy region) was observed as the MWNT loading increases. Maximum value of E' during glassy region was observed to be at 5 wt% with (7.26±0.7) E+08 Pa compared to neat epoxy. On the contrary, there is slight increased and slight decreased with E' values at 100 °C (rubbery region) for all nanocomposite. Since epoxy exhibits low thermal conductivity properties, addition of MWNT has enhanced the properties. Optimum value of thermal conductivity was observed at 3 wt%. The values increased up to 9.03 % compared to neat epoxy. As expected, the result showed decrease value in thermal conductivity at 5 wt% as a result of agglomeration of MWNT in the epoxy.

Three-Dimensional Graphene Foam Induces Multifunctionality in Epoxy Nanocomposites by Simultaneous Improvement in Mechanical, Thermal, and Electrical Properties.

PubMed

Embrey, Leslie; Nautiyal, Pranjal; Loganathan, Archana; Idowu, Adeyinka; Boesl, Benjamin; Agarwal, Arvind

2017-11-15

Three-dimensional (3D) macroporous graphene foam based multifunctional epoxy composites are developed in this study. Facile dip-coating and mold-casting techniques are employed to engineer microstructures with tailorable thermal, mechanical, and electrical properties. These processing techniques allow capillarity-induced equilibrium filling of graphene foam branches, creating epoxy/graphene interfaces with minimal separation. Addition of 2 wt % graphene foam enhances the glass transition temperature of epoxy from 106 to 162 °C, improving the thermal stability of the polymer composite. Graphene foam aids in load-bearing, increasing the ultimate tensile strength by 12% by merely 0.13 wt % graphene foam in an epoxy matrix. Digital image correlation (DIC) analysis revealed that the graphene foam cells restrict and confine the deformation of the polymer matrix, thereby enhancing the load-bearing capability of the composite. Addition of 0.6 wt % graphene foam also enhances the flexural strength of the pure epoxy by 10%. A 3D network of graphene branches is found to suppress and deflect the cracks, arresting mechanical failure. Dynamic mechanical analysis (DMA) of the composites demonstrated their vibration damping capability, as the loss tangent (tan δ) jumps from 0.1 for the pure epoxy to 0.24 for ∼2 wt % graphene foam-epoxy composite. Graphene foam branches also provide seamless pathways for electron transfer, which induces electrical conductivity exceeding 450 S/m in an otherwise insulator epoxy matrix. The epoxy-graphene foam composite exhibits a gauge factor as high as 4.1, which is twice the typical gauge factor for the most common metals. Simultaneous improvement in thermal, mechanical, and electrical properties of epoxy due to 3D graphene foam makes epoxy-graphene foam composite a promising lightweight and multifunctional material for aiding load-bearing, electrical transport, and motion sensing in aerospace, automotive, robotics, and smart device structures.

On the biomarkers and mechanisms of konzo, a distinct upper motor neuron disease associated with food (cassava) cyanogenic exposure.

PubMed

Kassa, Roman M; Kasensa, Nyamabo L; Monterroso, Victor H; Kayton, Robert J; Klimek, John E; David, Larry L; Lunganza, Kalala R; Kayembe, Kazadi T; Bentivoglio, Marina; Juliano, Sharon L; Tshala-Katumbay, Desire D

2011-03-01

Konzo is a self-limiting central motor-system disease associated with food dependency on cassava and low dietary intake of sulfur amino acids (SAA). Under conditions of SAA-deficiency, ingested cassava cyanogens yield metabolites that include thiocyanate and cyanate, a protein-carbamoylating agent. We studied the physical and biochemical modifications of rat serum and spinal cord proteins arising from intoxication of young adult rats with 50-200mg/kg linamarin, or 200mg/kg sodium cyanate (NaOCN), or vehicle (saline) and fed either a normal amino acid- or SAA-deficient diet for up to 2 weeks. Animals under SAA-deficient diet and treatment with linamarin or NaOCN developed hind limb tremors or motor weakness, respectively. LC/MS-MS analysis revealed differential albumin carbamoylation in animals treated with NaOCN, vs. linamarin/SAA-deficient diet, or vehicle. 2D-DIGE and MALDI-TOF/MS-MS analysis of the spinal cord proteome showed differential expression of proteins involved in oxidative mechanisms (e.g. peroxiredoxin 6), endocytic vesicular trafficking (e.g. dynamin 1), protein folding (e.g. protein disulfide isomerase), and maintenance of the cytoskeleton integrity (e.g. α-spectrin). Studies are needed to elucidate the role of the aformentioned modifications in the pathogenesis of cassava-associated motor-system disease. Copyright © 2010 Elsevier Ltd. All rights reserved.

Cross-species and tissue variations in cyanide detoxification rates in rodents and non-human primates on protein-restricted diet.

PubMed

Kimani, S; Moterroso, V; Morales, P; Wagner, J; Kipruto, S; Bukachi, F; Maitai, C; Tshala-Katumbay, D

2014-04-01

We sought to elucidate the impact of diet, cyanide or cyanate exposure on mammalian cyanide detoxification capabilities (CDC). Male rats (~8 weeks old) (N=52) on 75% sulfur amino acid (SAA)-deficient diet were treated with NaCN (2.5mg/kg bw) or NaOCN (50mg/kg bw) for 6 weeks. Macaca fascicularis monkeys (~12 years old) (N=12) were exclusively fed cassava for 5 weeks. CDC was assessed in plasma, or spinal cord, or brain. In rats, NaCN induced seizures under SAA-restricted diet whereas NaOCN induced motor deficits. No deficits were observed in non-human primates. Under normal diet, the CDC were up to ~80× faster in the nervous system (14 ms to produce one μmol of thiocyanate from the detoxification of cyanide) relative to plasma. Spinal cord CDC was impaired by NaCN, NaOCN, or SAA deficiency. In M. fascicularis, plasma CDC changed proportionally to total proteins (r=0.43; p<0.001). The plasma CDC was ~2× relative to that of rodents. The nervous system susceptibility to cyanide may result from a "multiple hit" by the toxicity of cyanide or its cyanate metabolite, the influences of dietary deficiencies, and the tissue variations in CDC. Chronic dietary reliance on cassava may cause metabolic derangement including poor CDC. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cross-species and tissue variations in cyanide detoxification rates in rodents and non-human primates on protein-restricted diet

PubMed Central

Kimani, S.; Moterroso, V.; Morales, P.; Wagner, J.; Kipruto, S.; Bukachi, F.; Maitai, C.; Tshala-Katumbay, D.

2014-01-01

We sought to elucidate the impact of diet, cyanide or cyanate exposure on mammalian cyanide detoxification capabilities (CDC). Male rats (~8 weeks old) (N=52) on 75% sulfur amino acid (SAA)-deficient diet were treated with NaCN (2.5 mg/kg bw) or NaOCN (50 mg/kg bw) for 6 weeks. Macaca fascicularis monkeys (~12 years old) (N=12) were exclusively fed cassava for 5 weeks. CDC was assessed in plasma, or spinal cord, or brain. In rats, NaCN induced seizures under SAA-restricted diet whereas NaOCN induced motor deficits. No deficits were observed in non-human primates. Under normal diet, the CDC were up to ~ 80X faster in the nervous system (14 milliseconds to produce one μmol of thiocyanate from the detoxification of cyanide) relative to plasma. Spinal cord CDC was impaired by NaCN, NaOCN, or SAA deficiency. In macaca fascicularis, plasma CDC changed proportionally to total proteins (r=0.43; p<0.001). The plasma CDC was ~ 2X relative to that of rodents. The nervous system susceptibility to cyanide may result from a “multiple hit” by the toxicity of cyanide or its cyanate metabolite, the influences of dietary deficiencies, and the tissue variations in CDC. Chronic dietary reliance on cassava may cause metabolic derangement including poor CDC. PMID:24500607

Chromatographic determination of nanomolar cyanate concentrations in estuarine and sea waters by precolumn fluorescence derivatization.

PubMed

Widner, Brittany; Mulholland, Margaret R; Mopper, Kenneth

2013-07-16

Recent studies suggest that cyanate (OCN(-)) is a potentially important source of reduced nitrogen (N) available to support the growth of aquatic microbes and, thus, may play a role in aquatic N cycling. However, aquatic OCN(-) distributions have not been previously described because of the lack of a suitable assay for measuring OCN(-) concentrations in natural waters. Previous methods were designed to quantify OCN(-) in aqueous samples with much higher reduced N concentrations (micromolar levels) than those likely to be found in natural waters (nanomolar levels). We have developed a method to quantify OCN(-) in dilute, saline environments. In the method described here, OCN(-) in aqueous solution reacts with 2-aminobenzoic acid to produce a highly fluorescent derivative, 2,4-quinazolinedione, which is then quantified using high performance liquid chromatography. Derivatization conditions were optimized to simultaneously minimize the reagent blank and maximize 2,4-quinazolinedione formation (>90% reaction yield) in estuarine and seawater matrices. A limit of detection (LOD) of 0.4 nM was achieved with only minor matrix effects. We applied this method to measure OCN(-) concentrations in estuarine and seawater samples from the Chesapeake Bay and coastal waters from the mid-Atlantic region. OCN(-) concentrations ranged from 0.9 to 41 nM. We determined that OCN(-) concentrations were stable in 0.2 μm filtered seawater samples stored at -80 °C for up to nine months.

Ferrate(VI) oxidation of zinc-cyanide complex.

PubMed

Yngard, Ria; Damrongsiri, Seelawut; Osathaphan, Khemarath; Sharma, Virender K

2007-10-01

Zinc-cyanide complexes are found in gold mining effluents and in metal finishing rinse water. The effect of Zn(II) on the oxidation of cyanide by ferrate(VI) (Fe(VI)O(4)(2-), Fe(VI)) was thus investigated by studying the kinetics of the reaction of Fe(VI) with cyanide present in a potassium salt of a zinc cyanide complex (K(2)Zn(CN)(4)) and in a mixture of Zn(II) and cyanide solutions as a function of pH (9.0-11.0). The rate-law for the oxidation of Zn(CN)(4)(2-) by Fe(VI) was found to be -d[Fe(VI)]/dt=k[Fe(VI)][Zn(CN)(4)(2-)](0.5). The rate constant, k, decreased with an increase in pH. The effect of temperature (15-45 degrees C) on the oxidation was studied at pH 9.0, which gave an activation energy of 45.7+/-1.5kJmol(-1). The cyanide oxidation rate decreased in the presence of the Zn(II) ions. However, Zn(II) ions had no effect on the cyanide removal efficiency by Fe(VI) and the stoichiometry of Fe(VI) to cyanide was approximately 1:1; similar to the stoichiometry in absence of Zn(II) ions. The destruction of cyanide by Fe(VI) resulted in cyanate. The experiments on removal of cyanide from rinse water using Fe(VI) demonstrated complete conversion of cyanide to cyanate.

40 CFR 721.9270 - Reaction product of epoxy with anhydride and glycerol and glycol.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Reaction product of epoxy with... Significant New Uses for Specific Chemical Substances § 721.9270 Reaction product of epoxy with anhydride and... substance identified generically as reaction product of epoxy with anhydride and glycerol and glycol (PMN P...

40 CFR 721.9270 - Reaction product of epoxy with anhydride and glycerol and glycol.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Reaction product of epoxy with... Significant New Uses for Specific Chemical Substances § 721.9270 Reaction product of epoxy with anhydride and... substance identified generically as reaction product of epoxy with anhydride and glycerol and glycol (PMN P...

40 CFR 721.9270 - Reaction product of epoxy with anhydride and glycerol and glycol.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Reaction product of epoxy with... Significant New Uses for Specific Chemical Substances § 721.9270 Reaction product of epoxy with anhydride and... substance identified generically as reaction product of epoxy with anhydride and glycerol and glycol (PMN P...

40 CFR 721.9270 - Reaction product of epoxy with anhydride and glycerol and glycol.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Reaction product of epoxy with... Significant New Uses for Specific Chemical Substances § 721.9270 Reaction product of epoxy with anhydride and... substance identified generically as reaction product of epoxy with anhydride and glycerol and glycol (PMN P...

40 CFR 721.9270 - Reaction product of epoxy with anhydride and glycerol and glycol.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Reaction product of epoxy with... Significant New Uses for Specific Chemical Substances § 721.9270 Reaction product of epoxy with anhydride and... substance identified generically as reaction product of epoxy with anhydride and glycerol and glycol (PMN P...

Are epoxy-wood bonds durable enough?

Treesearch

Charles R. Frihart

2005-01-01

An important aspect of any adhesive bond is that the bond maintains its integrity during its end use. Epoxies form highly durable bonds with many substrates but are usually not considered capable of forming completely durable bonds with wood by standard accelerated tests. However, epoxies are sold for wood boat construction, and some data have indicated that epoxies...

Toughened epoxy resin system and a method thereof

DOEpatents

Janke, C.J.; Dorsey, G.F.; Havens, S.J.; Lopata, V.J.

1998-03-10

Mixtures of epoxy resins with cationic initiators are curable under high energy ionizing radiation such as electron beam radiation, X-ray radiation, and gamma radiation. The composition of this process consists of an epoxy resin, a cationic initiator such as a diaryliodonium or triarylsulfonium salt of specific anions, and a toughening agent such as a thermoplastic, hydroxy-containing thermoplastic oligomer, epoxy-containing thermoplastic oligomer, reactive flexibilizer, rubber, elastomer, or mixture thereof. Cured compositions have high glass transition temperatures, good mechanical properties, and good toughness. These properties are comparable to those of similar thermally cured epoxies.

Toughened epoxy resin system and a method thereof

DOEpatents

Janke, Christopher J.; Dorsey, George F.; Havens, Stephen J.; Lopata, Vincent J.

1998-01-01

Mixtures of epoxy resins with cationic initiators are curable under high energy ionizing radiation such as electron beam radiation, X-ray radiation, and gamma radiation. The composition of this process consists of an epoxy resin, a cationic initiator such as a diaryliodonium or triarylsulfonium salt of specific anions, and a toughening agent such as a thermoplastic, hydroxy-containing thermoplastic oligomer, epoxy-containing thermoplastic oligomer, reactive flexibilizer, rubber, elastomer, or mixture thereof. Cured compositions have high glass transition temperatures, good mechanical properties, and good toughness. These properties are comparable to those of similar thermally cured epoxies.

Mechanical Reinforcement of Epoxy Composites with Carbon Fibers and HDPE

NASA Astrophysics Data System (ADS)

He, R.; Chang, Q.; Huang, X.; Li, J.

2018-01-01

Silanized carbon fibers (CFs) and a high-density polyethylene with amino terminal groups (HDPE) were introduced into epoxy resins to fabricate high-performance composites. A. mechanical characterization of the composites was performed to investigate the effect of CFs in cured epoxy/HDPE systems. The composites revealed a noticeable improvement in the tensile strength, elongation at break, flexural strength, and impact strength in comparison with those of neat epoxy and cured epoxy/HDPE systems. SEM micrographs showed that the toughening effect could be explained by yield deformations, phase separation, and microcracking.

Antibacterial activities effectuated by co-continuous epoxy-based polymer materials.

PubMed

Kubo, Takuya; Yasuda, Koji; Tominaga, Yuichi; Otsuka, Koji; Hosoya, Ken

2013-07-01

We report antibacterial activities of the epoxy-resin-based monolithic media (epoxy monoliths) having macroporous co-continuous structure as well as hydrophobic and/or hydrophilic surface. Utilizing epoxy monoliths containing ammonium groups, the antibacterial experiments were examined using Escherichia coli. As the results, the monolithic media prepared with an epoxy monomer having nitrogen atoms clearly showed antibacterial activities, while those prepared using the monomer without nitrogen atom showed less antibacterial activities. Additionally, the quaternization of the epoxy polymers were expressed significant antibacterial activities. Further studies elucidated that the observed antibacterial activities involved the steep effect based on pH changing of solution and hydrophobic interactions by the quaternary ammonium. Copyright © 2013 Elsevier B.V. All rights reserved.

Fiber-optic epoxy composite cure sensor. II. Performance characteristics

NASA Astrophysics Data System (ADS)

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

The performance of a fiber-optic epoxy composite cure sensor, as previously proposed, depends on the optical properties and the reaction kinetics of the epoxy. The reaction kinetics of a typical epoxy system are presented. It is a third-order autocatalytic reaction with a peak observed in each isothermal reaction-rate curve. A model is derived to describe the performance characteristics of the epoxy cure sensor. If a composite coupon is cured at an isothermal temperature, the sensor signal can be used to predict the time when the gel point occurs and to monitor the cure process. The sensor is also shown to perform well in nonstoichiometric epoxy matrices. In addition the sensor can detect the end of the cure without calibration.

Mechanical and Thermal Properties of Epoxy Composites Containing Zirconia-Impregnated Halloysite Nanotubes with Different Loadings.

PubMed

Kim, Suhyun; Kim, Moon Il; Shon, Minyoung; Seo, Bongkuk; Lim, Choongsun

2018-09-01

Epoxy resins are widely used in various industrial fields due to their low cost, good workability, heat resistance, and good mechanical strength. However, they suffer from brittleness, an issue that must be addressed for further applications. To solve this problem, additional fillers are needed to improve the mechanical and thermal properties of the resins; zirconia is one such filler. However, it has been reported that aggregation may occur in the epoxy composites as the amount of zirconia increases, preventing enhancement of the mechanical strength of the epoxy composites. Herein, to reduce the aggregation, zirconia was well dispersed on halloysite nanotubes (HNTs), which have high thermal and mechanical strength, by a conventional wet impregnation method. The HNTs were impregnated with zirconia at different loadings using zirconyl chloride octahydrate as a precursor. The mechanical and thermal strengths of the epoxy composites with these fillers were investigated. The zirconia-impregnated HNTs (Zr/HNT) were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and tunneling electron microscopy (TEM). The hardening conditions of the epoxy composites were analyzed by differential scanning calorimetry (DSC). The thermal strength of the epoxy composites was studied by thermomechanical analysis (TMA) and micro-calorimetry and the mechanical strength of the epoxy composites (flexural strength and tensile strength) was studied by using a universal testing machine (UTM). The mechanical and thermal strengths of the epoxy composites with Zr/HNT were improved compared to those of the epoxy composite with HNT, and also increased as the zirconia loading on HNT increased.

Epoxy composites coating with Fe3O4 decorated graphene oxide: Modified bio-inspired surface chemistry, synergistic effect and improved anti-corrosion performance

NASA Astrophysics Data System (ADS)

Zhan, Yingqing; Zhang, Jieming; Wan, Xinyi; Long, Zhihang; He, Shuangjiang; He, Yi

2018-04-01

To obtain graphene or graphene derivatives based epoxy composite coatings with high anti-corrosion performance, the morphology of nanostructures, dispersion, and interfacial adhesion are key factors that need to be considered. We here demonstrated the bio-inspired co-modification of graphene oxide/Fe3O4 hybrid (GO-Fe3O4@ poly (DA+KH550)) and its synergistic effect on the anti-corrosion performance of epoxy coating. For this purpose, graphene oxide/Fe3O4 hybrid obtained from hydrothermal route was modified by self-polymerization between dopamine and secondary functional monomer (KH550), which led to the modified bio-inspired surface functionalization. This novel modified bio-inspired functionalization was quite distinct from conventional surface modification or decoration. Namely, abundant amino groups were introduced by modified bio-inspired functionalization, which allowed the graphene oxide/Fe3O4 hybrid to disperse well in epoxy resin and enhanced the interfacial adhesion between modified nanofiller and epoxy resin through chemical crosslinking reaction. The electrochemical impedance spectroscopy (EIS) test revealed that anti-corrosive performance of epoxy coatings was significantly enhanced by addition of 0.5 wt% modified bio-inspired functionalized GO-Fe3O4 hybrid compared with neat epoxy and other nanofillers/epoxy composite coatings. Moreover, the micro-hardness of epoxy coating was enhanced by 71.8% compared with pure epoxy coating at the same loading content. In addition, the anticorrosion mechanism of GO-Fe3O4@poly (DA+KH550) was tentatively discussed.

Effect of Hygrothermal Aging on the Mechanical Properties of Fluorinated and Nonfluorinated Clay-Epoxy Nanocomposites

PubMed Central

Hamim, Salah U.; Singh, Raman P.

2014-01-01

Hydrophilic nature of epoxy polymers can lead to both reversible and irreversible/permanent changes in epoxy upon moisture absorption. The permanent changes leading to the degradation of mechanical properties due to combined effect of moisture and elevated temperature on EPON 862, Nanomer I.28E, and Somasif MAE clay-epoxy nanocomposites are investigated in this study. The extent of permanent degradation on fracture and flexural properties due to the hygrothermal aging is determined by drying the epoxy and their clay-epoxy nanocomposites after moisture absorption. Significant permanent damage is observed for fracture toughness and flexural modulus, while the extent of permanent damage is less significant for flexural strength. It is also observed that permanent degradation in Somasif MAE clay-epoxy nanocomposites is higher compared to Nanomer I.28E clay-epoxy nanocomposites. Fourier transform infrared (FTIR) spectroscopy revealed that both clays retained their original chemical structure after the absorption-desorption cycle without undergoing significant changes. Scanning electron microscopy (SEM) images of the fracture surfaces provide evidence that Somasif MAE clay particles offered very little resistance to crack propagation in case of redried specimens when compared to Nanomer I.28E counterpart. The reason for the observed higher extent of permanent degradation in Somasif MAE clay-epoxy system has been attributed to the weakening of the filler-matrix interface. PMID:27379285

Effect of Hygrothermal Aging on the Mechanical Properties of Fluorinated and Nonfluorinated Clay-Epoxy Nanocomposites.

PubMed

Hamim, Salah U; Singh, Raman P

2014-01-01

Hydrophilic nature of epoxy polymers can lead to both reversible and irreversible/permanent changes in epoxy upon moisture absorption. The permanent changes leading to the degradation of mechanical properties due to combined effect of moisture and elevated temperature on EPON 862, Nanomer I.28E, and Somasif MAE clay-epoxy nanocomposites are investigated in this study. The extent of permanent degradation on fracture and flexural properties due to the hygrothermal aging is determined by drying the epoxy and their clay-epoxy nanocomposites after moisture absorption. Significant permanent damage is observed for fracture toughness and flexural modulus, while the extent of permanent damage is less significant for flexural strength. It is also observed that permanent degradation in Somasif MAE clay-epoxy nanocomposites is higher compared to Nanomer I.28E clay-epoxy nanocomposites. Fourier transform infrared (FTIR) spectroscopy revealed that both clays retained their original chemical structure after the absorption-desorption cycle without undergoing significant changes. Scanning electron microscopy (SEM) images of the fracture surfaces provide evidence that Somasif MAE clay particles offered very little resistance to crack propagation in case of redried specimens when compared to Nanomer I.28E counterpart. The reason for the observed higher extent of permanent degradation in Somasif MAE clay-epoxy system has been attributed to the weakening of the filler-matrix interface.

Comparative study on Ti/Zr/V and chromate conversion treated aluminum alloys: Anti-corrosion performance and epoxy coating adhesion properties

NASA Astrophysics Data System (ADS)

Zhu, Wen; Li, Wenfang; Mu, Songlin; Fu, Nianqing; Liao, Zhongmiao

2017-05-01

In this study, a Ti/Zr/V conversion coating (TZVCC) was deposited on the surface of aluminum alloy 6063 (AA6063) as an alternative of the chromate conversion coating (CCC). Both the TZVCC treated AA6063 (TZVCC/AA6063) and CCC treated AA6063 (CCC/AA6063) were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and contact angle measuring device. The anti-corrosion performance of the TZVCC/AA6063 and CCC/AA6063 was evaluated by electrochemical measurements and neutral salt spray tests. It showed that both the surface roughness and surface free energy of the AA6063 were significantly increased after TZVCC treatment. The anti-corrosion performance of TZVCC/AA6063 was superior to that of CCC/AA6063. In addition, the effects of the TZVCC and CCC on the adhesion properties and anti-corrosion performance of epoxy coating applied on samples were examined by pull-off tests and electrochemical impedance spectroscopy (EIS). The dry, wet and recovery adhesive strengths of the epoxy coating on TZVCC treated samples (epoxy coated TZVCC/AA6063) were very close to those of epoxy coating on CCC treated ones (epoxy coated CCC/AA6063). The epoxy coated TZVCC/AA6063 showed better corrosion resistance than the epoxy coated CCC/AA6063 and epoxy coated AA6063.

Method for Improving Acoustic Impedance of Epoxy Resins

DTIC Science & Technology

2010-06-11

neoprene, ethylene propylene diene monomer ( EPDM ) and polyurethane rubbers . Typical applications of these materials encapsulate and protect acoustic...different material (e.g., rubber ) cannot be used. Thus, a hard, strong and acoustically transparent material is needed. Suitable high modulus...epoxy resin. In this method, an epoxy resin component is mixed with a rubber component. The epoxy resin component is preferably a bisphenol A

Dynamic Loading Characteristics in Metals and Composites

DTIC Science & Technology

2009-12-01

Armenakas and Sciammarella [6] reported experimental findings on the mechanical properties of glass fiber reinforced epoxy plates subjected to high rates... Sciammarella [6] Glass/epoxy Decrease Increase Decrease - Lifshitz [7] Angle ply glass/epoxy Increase Independent Independent - Daniel et al...Armenakas, and C. A. Sciammarella , “Response of glass-fiber-reinforced epoxy specimens to high rates of tensile loading,” Experimental Mechanics, vol

A new approach to raising heat resistance of epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Korobko, Anatoliy P.; Levakova, Irina V.; Krasheninnikov, Sergey V.

2012-07-01

A new approach to enhancing heat resistance of epoxy nanocomposites is offered. Complete exfoliation of montmorillonite particles into individual platelets (nanoparticles) is not sufficient condition for increasing the glass transition temperature of the epoxy nanocomposite. A much higher contribution to the increase in the heat resistance is ensured by grafting of epoxy molecular chains onto the surface of aluminosilicate platelets.

Curing Effects on Interfacial Adhesion between Recycled Carbon Fiber and Epoxy Resin Heated by Microwave Irradiation

PubMed Central

Shimamoto, Daisuke; Hotta, Yuji

2018-01-01

The interfacial adhesion of recycled carbon fiber (CF) reinforced epoxy composite heated by microwave (MW) irradiation were investigated by changing the curing state of the epoxy resin. The recycled CF was recovered from the composite, which was prepared by vacuum-assisted resin transfer molding, by thermal degradation at 500 or 600 °C. Thermogravimetric analysis showed that the heating at 600 °C caused rough damage to the CF surface, whereas recycled CF recovered at 500 °C have few defects. The interfacial shear strength (IFSS) between recycled CF and epoxy resin was measured by a single-fiber fragmentation test. The test specimen was heated by MW after mixing the epoxy resin with a curing agent or pre-curing, in order to investigate the curing effects on the matrix resin. The IFSSs of the MW-irradiated samples were significantly varied by the curing state of the epoxy resin and the surface condition of recycled CF, resulting that they were 99.5 to 131.7% of oven heated samples Furthermore, rheological measurements showed that the viscosity and shrinking behaviors of epoxy resin were affected based on the curing state of epoxy resin before MW irradiation. PMID:29587422

[Contact allergy to epoxy resins plastics based on materials collected by the Nofer Institute of Occupational Medicine].

PubMed

Kieć-Swierczyńska, Marta; Krecisz, Beata

2003-01-01

Of the 5604 patients examined in 1984-2001 for suspected occupational dermatitis, 160 persons (2.8%) showed allergy to epoxy resins plastics. Allergy was more frequent in men (4.9%) than in women (1.2%); in 154 persons, allergy was of occupational etiology (in a group of 160 patients with allergy to epoxy resins, the following proportions were observed: bricklayers, platelayers--17.5%; fitters, turners, machinist millers--13.8%; plastics molders--13.1%; laminators--11.3%; electrical equipment assemblers--10.6%; painters--10.0%). Having compared the frequency of allergy to components of epoxy resins in the years 1984-1993 and 1994-2001, it was found that allergy to resin, reactive diluents and plasticizers was on increase, whereas allergy to amines and acid anhydrides hardeners was on decrease. In a group of 13 chemical compounds entering into the composition of epoxy resins, epoxy resin contributed to the largest number of positive patch tests (77.5% of epoxy-allergic persons). This was followed by triethylenetetramine (23.1%), ethylenediamine (13.1%), phthalic anhydride (8.1%), diethylenetetramine (6.9%) and phenylglycidylether (6.2%). In addition, three patients reacted to both epoxy resin and cycloaliphatic resin.

Progress toward Making Epoxy/Carbon-Nanotube Composites

NASA Technical Reports Server (NTRS)

Tiano, Thomas; Roylance, Margaret; Gassner, John; Kyle, William

2008-01-01

A modicum of progress has been made in an effort to exploit single-walled carbon nanotubes as fibers in epoxy-matrix/fiber composite materials. Two main obstacles to such use of carbon nanotubes are the following: (1) bare nanotubes are not soluble in epoxy resins and so they tend to agglomerate instead of becoming dispersed as desired; and (2) because of lack of affinity between nanotubes and epoxy matrices, there is insufficient transfer of mechanical loads between the nanotubes and the matrices. Part of the effort reported here was oriented toward (1) functionalization of single-walled carbon nanotubes with methyl methacrylate (MMA) to increase their dispersability in epoxy resins and increase transfer of mechanical loads and (2) ultrasonic dispersion of the functionalized nanotubes in tetrahydrofuran, which was used as an auxiliary solvent to aid in dispersing the functionalized nanotubes into a epoxy resin. In another part of this effort, poly(styrene sulfonic acid) was used as the dispersant and water as the auxiliary solvent. In one experiment, the strength of composite of epoxy with MMA-functionalized-nanotubes was found to be 29 percent greater than that of a similar composite of epoxy with the same proportion of untreated nanotubes.

Curing Effects on Interfacial Adhesion between Recycled Carbon Fiber and Epoxy Resin Heated by Microwave Irradiation.

PubMed

Tominaga, Yuichi; Shimamoto, Daisuke; Hotta, Yuji

2018-03-26

The interfacial adhesion of recycled carbon fiber (CF) reinforced epoxy composite heated by microwave (MW) irradiation were investigated by changing the curing state of the epoxy resin. The recycled CF was recovered from the composite, which was prepared by vacuum-assisted resin transfer molding, by thermal degradation at 500 or 600 °C. Thermogravimetric analysis showed that the heating at 600 °C caused rough damage to the CF surface, whereas recycled CF recovered at 500 °C have few defects. The interfacial shear strength (IFSS) between recycled CF and epoxy resin was measured by a single-fiber fragmentation test. The test specimen was heated by MW after mixing the epoxy resin with a curing agent or pre-curing, in order to investigate the curing effects on the matrix resin. The IFSSs of the MW-irradiated samples were significantly varied by the curing state of the epoxy resin and the surface condition of recycled CF, resulting that they were 99.5 to 131.7% of oven heated samples Furthermore, rheological measurements showed that the viscosity and shrinking behaviors of epoxy resin were affected based on the curing state of epoxy resin before MW irradiation.

Enhancement of mechanical properties of epoxy/graphene nanocomposite

NASA Astrophysics Data System (ADS)

Berhanuddin, N. I. C.; Zaman, I.; Rozlan, S. A. M.; Karim, M. A. A.; Manshoor, B.; Khalid, A.; Chan, S. W.; Meng, Q.

2017-10-01

Graphene is a novel class of nanofillers possessing outstanding characteristics including most compatible with most polymers, high absolute strength, high aspect ratio and cost effectiveness. In this study, graphene was used to reinforce epoxy as a matrix, to enhance its mechanical properties. Two types of epoxy composite were developed which are epoxy/graphene nanocomposite and epoxy/modified graphene nanocomposite. The fabrication of graphene was going through thermal expansion and sonication process. Chemical modification was only done for modified graphene where 4,4’-Methylene diphenyl diisocyanate (MDI) is used. The mechanical properties of both nanocomposite, such as Young’s modulus and maximum stress were investigated. Three weight percentage were used for this study which are 0.5 wt%, 1.0 wt% and 1.5 wt%. At 0.5 wt%, modified and unmodified shows the highest value compared to neat epoxy, where the value were 8 GPa, 6 GPa and 0.675 GPa, respectively. For maximum stress, neat epoxy showed the best result compared to both nanocomposite due to the changes of material properties when adding the filler into the matrix. Therefore, both nanocomposite increase the mechanical properties of the epoxy, however modification surface of graphene gives better improvement.

Thermal-mechanical properties of a graphitic-nanofibers reinforced epoxy.

PubMed

Salehi-Khojin, Amin; Jana, Soumen; Zhong, Wei-Hong

2007-03-01

We previously developed a series of reactive graphitic nanofibers (r-GNFs) reinforced epoxy (nano-epoxy) as composite matrices, which have shown good wetting and adhesion properties with continuous fiber. In this work, the thermal-mechanical properties of the nano-epoxy system containing EponTM Resin 828 and Epi-cure Curing Agent W were characterized. Results from three-point bending tests showed that the flexural strength and flexural modulus of this system with 0.30 wt% of reactive nanofibers were increased by 16%, and 21% respectively, over pure epoxy. Fracture toughness increased by ca. 40% for specimens with 0.50 wt% of r-GNFs. By dynamic mechanical analysis (DMA) test, specimens with 0.30 wt% of r-GNFs showed a significant increase in storage modulus E' (by ca. 122%) and loss modulus E" (by ca. 111%) with respect to that of pure epoxy. Also thermo-dilatometry analysis (TDA) was used to measure dimensional change of specimens as a function of temperature, and then, coefficients of thermal expansion (CTE) before and after glass transition temperature (Tg) were obtained. Results implied that nano-epoxy materials had good dimensional stability and reduced CTE values when compared to those of pure epoxy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kesgin, Ibrahim; Hasse, Quentin; Ivanyushenkov, Yury

The use of second-generation high-temperature superconducting-coated conductors enables an enhancement of the performance of undulator magnets. However, preventing the motion of the wire and providing sufficient conduction cooling to the winding stacks have remained challenges. In this study, we have evaluated epoxy impregnation techniques to address these issues. Epoxy resin was prepared with different nanopowders and the effect on the performance of the undulator coil pack was investigated. All epoxy impregnated coils showed smaller n values and some degree of deterioration of the critical current I c. The I c degradation was most pronounced for epoxy mixed with high aspectmore » ratio multiwalled carbon nanotubes (MWCNTs). It has been found that the crack formation in the epoxy results in plastic deformation of the copper stabilizer layer, which causes the underlying ceramic REBCO superconducting layer to crack resulting in degradation of the superconducting tape performance. As a result, careful adjustment of epoxy thickness surrounding the superconductor and the powder ratio in the epoxy eliminate the performance degradation.« less

Mechanical and anticorrosive properties of graphene/epoxy resin composites coating prepared by in-situ method.

PubMed

Zhang, Zhiyi; Zhang, Wenhui; Li, Diansen; Sun, Youyi; Wang, Zhuo; Hou, Chunling; Chen, Lu; Cao, Yang; Liu, Yaqing

2015-01-20

The graphene nanosheets-based epoxy resin coating (0, 0.1, 0.4 and 0.7 wt %) was prepared by a situ-synthesis method. The effect of polyvinylpyrrolidone/reduced graphene oxide (PVP-rGO) on mechanical and thermal properties of epoxy resin coating was investigated using nanoindentation technique and thermogravimetric analysis, respectively. A significant enhancement (ca. 213% and 73 °C) in the Young modulus and thermal stability of epoxy resin coating was obtained at a loading of 0.7 wt %, respectively. Furthermore, the erosion resistance of graphene nanosheets-based epoxy resin coating was investigated by electrochemical measurement. The results showed also that the Rrcco (ca. 0.3 mm/year) of graphene nanosheets-based epoxy resin coating was far lower than neat epoxy resin (1.3 mm/year). Thus, this approach provides a novel route for improving erosion resistance and mechanical-thermal stability of polymers coating, which is expected to be used in mechanical-thermal-corrosion coupling environments.

Contact allergy to an epoxy reactive diluent: 1,4-butanediol diglycidyl ether.

PubMed

Jolanki, R; Estlander, T; Kanerva, L

1987-02-01

3 female workers in a brush factory developed contact allergy from a 2-component epoxy glue containing epoxy resin (37% w/w), reactive diluents: i.e., 1,4-butanediol diglycidyl ether (BDDGE) 3%, glycidyl ethers of aliphatic alcohols (Epoxide 8) 0.03% and phenyl glycidyl ether (PGE) 0.01%; and inert fillers. All 3 patients were positive to the resin component of the glue and to BDDGE, indicating that BDDGE was the main allergen. 2 of the patients reacted to PGE, but none to the 3rd reactive diluent (Epoxide 8) in the glue. 2 of the patients did not react to epoxy resin, indicating that BDDGE may be an even stronger sensitizer in humans than epoxy resin, and that it does not cross-react with epoxy resins. Permeation studies revealed that BDDGE penetrates disposable PVC and rubber gloves in less than 30 min; thus, contaminated gloves should be replaced immediately. Reactive diluents should be included in patch test series if contact allergy to epoxy products is suspected.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keeratitham, Waralee, E-mail: waralee.ke@student.chula.ac.th; Somwangthanaroj, Anongnat, E-mail: anongnat.s@chula.ac.th

Herein, our main objective is to prepare the fast curing epoxy system with high glass transition temperature (T{sub g}) by incorporating the multifunctional epoxy resin into the mixture of diglycidyl ether of bisphenol A (DGEBA) as a major epoxy component and aromatic diamine as a hardener. Furthermore, the curing behavior as well as thermal and thermomechanical properties were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). It was found that T{sub g} obtained from tan δ of DGEBA/aromatic diamine system increased from 100 °C to 205 °C with the presence of 30 percentage bymore » weight of multifunctional epoxy resin. Additionally, the isothermal DSC results showed that the multifunctional epoxy resin can accelerate the curing reaction of DGEBA/aromatic diamine system. Namely, a high degree of curing (∼90%) was achieved after a few minutes of curing at low temperature of 130 °C, owing to a large number of epoxy ring of multifunctional epoxy resin towards the active hydrogen atoms of aromatic diamine.« less

Mechanical and Anticorrosive Properties of Graphene/Epoxy Resin Composites Coating Prepared by in-Situ Method

PubMed Central

Zhang, Zhiyi; Zhang, Wenhui; Li, Diansen; Sun, Youyi; Wang, Zhuo; Hou, Chunling; Chen, Lu; Cao, Yang; Liu, Yaqing

2015-01-01

The graphene nanosheets-based epoxy resin coating (0, 0.1, 0.4 and 0.7 wt %) was prepared by a situ-synthesis method. The effect of polyvinylpyrrolidone/reduced graphene oxide (PVP-rGO) on mechanical and thermal properties of epoxy resin coating was investigated using nanoindentation technique and thermogravimetric analysis, respectively. A significant enhancement (ca. 213% and 73 °C) in the Young modulus and thermal stability of epoxy resin coating was obtained at a loading of 0.7 wt %, respectively. Furthermore, the erosion resistance of graphene nanosheets-based epoxy resin coating was investigated by electrochemical measurement. The results showed also that the Rrcco (ca. 0.3 mm/year) of graphene nanosheets-based epoxy resin coating was far lower than neat epoxy resin (1.3 mm/year). Thus, this approach provides a novel route for improving erosion resistance and mechanical-thermal stability of polymers coating, which is expected to be used in mechanical-thermal-corrosion coupling environments. PMID:25608656

Modification of the Interfacial Interaction between Carbon Fiber and Epoxy with Carbon Hybrid Materials

PubMed Central

Yu, Kejing; Wang, Menglei; Wu, Junqing; Qian, Kun; Sun, Jie; Lu, Xuefeng

2016-01-01

The mechanical properties of the hybrid materials and epoxy and carbon fiber (CF) composites were improved significantly as compared to the CF composites made from unmodified epoxy. The reasons could be attributed to the strong interfacial interaction between the CF and the epoxy composites for the existence of carbon nanomaterials. The microstructure and dispersion of carbon nanomaterials were characterized by transmission electron microscopy (TEM) and optical microscopy (OM). The results showed that the dispersion of the hybrid materials in the polymer was superior to other carbon nanomaterials. The high viscosity and shear stress characterized by a rheometer and the high interfacial friction and damping behavior characterized by dynamic mechanical analysis (DMA) indicated that the strong interfacial interaction was greatly improved between fibers and epoxy composites. Remarkably, the tensile tests presented that the CF composites with hybrid materials and epoxy composites have a better reinforcing and toughening effect on CF, which further verified the strong interfacial interaction between epoxy and CF for special structural hybrid materials. PMID:28335217

Method for epoxy foam production using a liquid anhydride

DOEpatents

Celina, Mathias [Albuquerque, NM

2012-06-05

An epoxy resin mixture with at least one epoxy resin of between approximately 50 wt % and 100 wt %, an anhydride cure agent of between approximately 0 wt % and approximately 50 wt %, a tert-butoxycarbonyl anhydride foaming agent of between proximately 0.1-20 wt %, a surfactant and an imidazole or similar catalyst of less than approximately 2 wt %, where the resin mixture is formed from at least one epoxy resin with a 1-10 wt % tert-butoxycarbonyl anhydride compound and an imidazole catalyst at a temperature sufficient to keep the resin in a suitable viscosity range, the resin mixture reacting to form a foaming resin which in the presence of an epoxy curative can then be cured at a temperature greater than 50.degree. C. to form an epoxy foam.

Electrical and Mechanical Properties of 3D-Printed Graphene-Reinforced Epoxy

NASA Astrophysics Data System (ADS)

Compton, Brett G.; Hmeidat, Nadim S.; Pack, Robert C.; Heres, Maximilian F.; Sangoro, Joshua R.

2018-03-01

Recent developments in additive manufacturing have demonstrated the potential for thermoset polymer feedstock materials to achieve high strength, stiffness, and functionality through incorporation of structural and functional filler materials. In this work, graphene was investigated as a potential filler material to provide rheological properties necessary for direct-write three-dimensional (3D) printing and electrostatic discharge properties to the printed component. The rheological properties of epoxy/graphene mixtures were characterized, and printable epoxy/graphene inks formulated. Sheet resistance values for printed epoxy/graphene composites ranged from 0.67 × 102 Ω/sq to 8.2 × 103 Ω/sq. The flexural strength of printed epoxy/graphene composites was comparable to that of cast neat epoxy ( 80 MPa), suggesting great potential for these new materials in multifunctional 3D-printed devices.

The Effect of Water on the Work of Adhesion at Epoxy Interfaces by Molecular Dynamics Simulation

NASA Technical Reports Server (NTRS)

Hinkley, J.A.; Frankland, S.J.V.; Clancy, T.C.

2009-01-01

Molecular dynamics simulation can be used to explore the detailed effects of chemistry on properties of materials. In this paper, two different epoxies found in aerospace resins are modeled using molecular dynamics. The first material, an amine-cured tetrafunctional epoxy, represents a composite matrix resin, while the second represents a 177 C-cured adhesive. Surface energies are derived for both epoxies and the work of adhesion values calculated for the epoxy/epoxy interfaces agree with experiment. Adding water -- to simulate the effect of moisture exposure -- reduced the work of adhesion in one case, and increased it in the other. To explore the difference, the various energy terms that make up the net work of adhesion were compared and the location of the added water was examined.

Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure

NASA Astrophysics Data System (ADS)

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

Colorless triphenylamine-based aliphatic thermoset epoxy for multicolored and near-infrared electrochromic applications.

PubMed

Chuang, Ya-Wen; Yen, Hung-Ju; Wu, Jia-Hao; Liou, Guey-Sheng

2014-03-12

In this study, two novel colorless thermoset epoxy resins with anodically electrochromism were prepared from the thermal curing of two triphenylamine-based diamine monomers, 4,4'-diamino-4″-methoxytriphenylamine (1) and N,N'-bis(4-aminophenyl)-N,N'-di(4-methoxylphenyl)-1,4-phenylenediamine (2) with aliphatic epoxy triglycidyl isocyanurate, respectively. The resulting thermoset epoxy resins showed excellent softening temperature (Ts, 270 and 280 °C) due to the rigid structure and highly crosslinking density. In addition, novel colorless epoxy resin films revealed good reversible electrochemical oxidation and interesting multi-electrochromic behavior with high contrast ratio both in visible and near-infrared regions. The aliphatic thermoset epoxy resins also exhibited high transparency in visible region as colorless and great potential for practical electrochromic applications.

Process for epoxy foam production

DOEpatents

Celina, Mathias C [Albuquerque, NM

2011-08-23

An epoxy resin mixture with at least one epoxy resin of between approximately 60 wt % and 90 wt %, a maleic anhydride of between approximately 1 wt % and approximately 30 wt %, and an imidazole catalyst of less than approximately 2 wt % where the resin mixture is formed from at least one epoxy resin with a 1-30 wt % maleic anhydride compound and an imidazole catalyst at a temperature sufficient to keep the maleic anhydride compound molten, the resin mixture reacting to form a foaming resin which can then be cured at a temperature greater than 50.degree. C. to form an epoxy foam.

Lightweight Forms for Epoxy/Aramid Ducts

NASA Technical Reports Server (NTRS)

Mix, E. W.; Anderson, A. N.; Bedford, Donald L., Sr.

1986-01-01

Aluminum mandrels easy to remove. Lightweight aluminum mandrel for shaping epoxy/aramid ducts simplifies and speeds production. In new process, glass-reinforced epoxy/aramid cloth wrapped on aluminum mandrel. Stainless-steel flanges and other hardware fitted on duct and held by simple tooling. Entire assembly placed in oven to cure epoxy. After curing, assembly placed in alkaline bath dissolves aluminum mandrel in about 4 hours. Epoxy/aramid shell ready for use as duct. Aluminum mandrel used to make ducts of various inside diameters up to 6 in. Standard aluminum forms used. Conventional tube-bending equipment produces requisite curves in mandrels.

An investigation of chemically-induced improvement in saturation moisture characteristics of epoxies

NASA Technical Reports Server (NTRS)

Singh, J. J.; St.clair, T. L.; Stoakley, D. M.

1984-01-01

MY-720/DDS epoxy samples were treated with three selected chemical compounds to render the active H-sites inactive for moisture absorption. Treating the epoxy castings with acetyl chloride and dichlorodimethyl silane leads only to surface changes indicating that these molecules are too large to penetrate the epoxy castings. Boron trifluoride, on the other hand, does penetrate the epoxy chain as is indicated by the formation of green domains in the interior of the castings. However, the process of saturating the specimens with moisture appears to leach out the chemical additives--thereby nullifying their possible ameliorative effects.

Enhanced protective properties of epoxy/polyaniline-camphorsulfonate nanocomposite coating on an ultrafine-grained metallic surface

NASA Astrophysics Data System (ADS)

Pour-Ali, Sadegh; Kiani-Rashid, Alireza; Babakhani, Abolfazl; Davoodi, Ali

2016-07-01

An ultrafine-grained surface layer on mild steel substrate with average grain size of 77 nm was produced through wire brushing process. Surface grain size was determined through transmission electron microscopy and X-ray diffraction methods. This substrate was coated with epoxy and an in situ synthesized epoxy/polyaniline-camphorsulfonate (epoxy/PANI-CSA) nanocomposite. The corrosion behavior was studied by open circuit potential, potentiodynamic polarization and impedance measurements. Results of electrochemical tests evidenced the enhanced protective properties of epoxy/PANI-CSA coating on the substrate with ultrafine-grained surface.

Evaluation of interlaminar shear of laminate by 3D digital holography

NASA Astrophysics Data System (ADS)

Mayssa, Karray; Christophe, Poilane; Mohamed, Gargouri; Pascal, Picart

2017-05-01

In this paper, we propose a three-color holographic interferometer devoted to the 3D displacement field analysis of a composite material. The method in applied to analyze cracks during a short beam shear test. The tested materials are a glass/epoxy composite, a flax/carbon/epoxy composite and a flax/epoxy composite. Such an evaluation provides a pertinent parameter to detect premature cracks in the structure, long before it becomes visible on the real time stress/strain curve, or with a classical microscope. Moreover, the mechanical proprieties of flax/carbon/epoxy composite and flax/epoxy composite are compared.

Molecular Modeling of Aerospace Polymer Matrices Including Carbon Nanotube-Enhanced Epoxy

NASA Astrophysics Data System (ADS)

Radue, Matthew S.

Carbon fiber (CF) composites are increasingly replacing metals used in major structural parts of aircraft, spacecraft, and automobiles. The current limitations of carbon fiber composites are addressed through computational material design by modeling the salient aerospace matrix materials. Molecular Dynamics (MD) models of epoxies with and without carbon nanotube (CNT) reinforcement and models of pure bismaleimides (BMIs) were developed to elucidate structure-property relationships for improved selection and tailoring of matrices. The influence of monomer functionality on the mechanical properties of epoxies is studied using the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. The results demonstrate an increase in stiffness and yield strength with increasing resin functionality. Comparison between the network structures of distinct epoxies is further advanced by the Monomeric Degree Index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli for all epoxies modeled. Therefore, the ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. While epoxies have been well-studied using MD, there has been no concerted effort to model cured BMI polymers due to the complexity of the network-forming reactions. A novel, adaptable crosslinking framework is developed for implementing 5 distinct cure reactions of Matrimid-5292 (a BMI resin) and investigating the network structure using MD simulations. The influence of different cure reactions and extent of curing are analyzed on the several thermo-mechanical properties such as mass density, glass transition temperature, coefficient of thermal expansion, elastic moduli, and thermal conductivity. The developed crosslinked models correctly predict experimentally observed trends for various properties. Finally, the epoxies modeled (di-, tri-, and tetra-functionalresins) are simulated with embedded CNT to understand how the affinity to nanoparticles affects the mechanical response. Multiscale modeling techniques are then employed to translate the molecular phenomena observed to predict the behavior of realistic composites. The effective stiffness of hybrid composites are predicted for CNT/epoxy composites with randomly oriented CNTs, for CF/CNT/epoxy systems with aligned CFs and randomly oriented CNTs, and for woven CF/CNT/epoxy fabric with randomly oriented CNTs. The results indicate that in the CNT/epoxy systems the epoxy type has a significant influence on the elastic properties. For the CF/CNT/epoxy hybrid composites, the axial modulus is highly influenced by CF concentration, while the transverse modulus is primarily affected by the CNT weight fraction.

Electrical properties of epoxies used in hybrid microelectronics

NASA Technical Reports Server (NTRS)

Stout, C. W.

1976-01-01

The electrical properties and basic characteristics of the structure of conductive epoxies were studied. The results of the experimental work performed to measure the electrical properties of epoxies are presented.

Method for Improving Acoustic Impedance of Epoxy Resins

DTIC Science & Technology

2010-06-21

include neoprene, ethylene propylene diene monomer ( EPDM ) and polyurethane rubbers . Typical applications of these materials encapsulate and protect...a different material (e.g., rubber ) cannot be used. Thus, a hard, strong and acoustically transparent material is needed. Suitable high modulus...an epoxy resin. In this method, an epoxy resin component is mixed with a rubber component. The epoxy resin component is preferably a bisphenol A

40 CFR 180.1283 - (Z)-7,8-epoxy-2-methyloctadecane (Disparlure); exemption from the requirement of a tolerance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 25 2013-07-01 2013-07-01 false (Z)-7,8-epoxy-2-methyloctadecane... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1283 (Z)-7,8-epoxy-2-methyloctadecane... is established for residues of (Z)-7,8-epoxy-2-methyloctadecane on all food and feed crops that occur...

40 CFR 180.1283 - (Z)-7,8-epoxy-2-methyloctadecane (Disparlure); exemption from the requirement of a tolerance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 24 2011-07-01 2011-07-01 false (Z)-7,8-epoxy-2-methyloctadecane... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1283 (Z)-7,8-epoxy-2-methyloctadecane... is established for residues of (Z)-7,8-epoxy-2-methyloctadecane on all food and feed crops that occur...

40 CFR 180.1283 - (Z)-7,8-epoxy-2-methyloctadecane (Disparlure); exemption from the requirement of a tolerance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false (Z)-7,8-epoxy-2-methyloctadecane... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1283 (Z)-7,8-epoxy-2-methyloctadecane... is established for residues of (Z)-7,8-epoxy-2-methyloctadecane on all food and feed crops that occur...

40 CFR 180.1283 - (Z)-7,8-epoxy-2-methyloctadecane (Disparlure); exemption from the requirement of a tolerance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 25 2012-07-01 2012-07-01 false (Z)-7,8-epoxy-2-methyloctadecane... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1283 (Z)-7,8-epoxy-2-methyloctadecane... is established for residues of (Z)-7,8-epoxy-2-methyloctadecane on all food and feed crops that occur...

40 CFR 180.1283 - (Z)-7,8-epoxy-2-methyloctadecane (Disparlure); exemption from the requirement of a tolerance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 24 2014-07-01 2014-07-01 false (Z)-7,8-epoxy-2-methyloctadecane... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1283 (Z)-7,8-epoxy-2-methyloctadecane... is established for residues of (Z)-7,8-epoxy-2-methyloctadecane on all food and feed crops that occur...

Siloxane Modifiers for Epoxy Resins.

DTIC Science & Technology

1983-12-01

similarly prepared ATBN- and CTBN -modified epoxies. Wear rate was quite dramatically reduced with some of the modifiers. Wear results are discussed in...similarly prepared ATBN- and CTBN -modified epoxies. Wear rate was quite dramatically reduced with some of the modifiers. Wear results are discussed...acrylonitrile copolymers having both carboxyl ( CTBN ) and amine (ATBN) end groups have been widely used as epoxy modifiers (4-11). During the curing process, the

Air Quality Management Using Pollution Prevention: A Joint Service Approach

DTIC Science & Technology

1998-03-01

sites to promote polymerization. High solids coatings may be one or two component systems based on acrylic , alkyd , epoxy, polyester, or urethane...formulation to form high molecular weight polymers. Examples include acrylic , epoxy/polyester hybrid , functional epoxy, thin film epoxy, and urethane...Air Human System Center (HSC/OEBQ) Naval Facilities Engineering Service Center (NFESC) 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 9

Uranium and thorium complexes of the phosphaethynolate ion

DOE PAGES

Camp, Clément; Settineri, Nicholas; Lefèvre, Julia; ...

2015-06-20

New tris-amidinate actinide (Th, U) complexes containing a rare O-bound terminal phosphaethynolate (OCP⁻) ligand were synthesized and fully characterized. The cyanate (OCN⁻) and thiocyanate (SCN⁻) analogs were prepared for comparison and feature a preferential N-coordination to the actinide metals. The Th(amid) 3(OCP) complex reacts with Ni(COD) 2 to yield the heterobimetallic adduct (amid) 3Th(μ-η 1(O):η 2(C,P)-OCP)Ni(COD) featuring an unprecedented reduced (OCP⁻) bent fragment bridging the two metals.

Syntheses of organic compounds in the presence of the fused iron catalyst and their mechanisms and kinetics

NASA Astrophysics Data System (ADS)

Glebov, L. S.; Kliger, G. A.

1989-10-01

New synthetic possibilities of the reduced promoted fused iron catalyst in intermolecular and intramolecular amination, cyanation, hydrogenation-dehydrogenation, and hydrodeoxygenation reactions and intermolecular and intramolecular dehydration, polymerisation, and isotope exchange are examined. The mechanisms and kinetics of the reactions leading to the synthesis of amines, alcohols, hydrocarbons, and other organic compunds are discussed. A laser Raman spectroscopic method is described for the investigation of heterogeneous organic catalysis in situ. The bibliography includes 148 references.

Multifunctional Macromolecules

DTIC Science & Technology

1993-10-01

wash bottles. This converts the highly toxic HCN into relatively harmless sodium cyanate . Draege tube "sniffers" were used inside the hood to detect...thickness of 4 pm and metallized with a 100 nm thick gold electrode. Using a dc power supply and a picoammeter, steady state photoconduction...analyze the data obtained using P2ANS in this work. I An 8 pm sample of 50/50 P2ANS/MMA was metallized and poled at 100 V/pm for 5 minutes at 140*C. The

Virtually Instantaneous, Room-temperature [11C]-Cyanation Using Biaryl Phosphine Pd(0) Complexes

PubMed Central

Lee, Hong Geun; Milner, Phillip J.; Placzek, Michael S.; Buchwald, Stephen L.; Hooker, Jacob M.

2015-01-01

A new radiosynthetic protocol for the preparation of [11C]aryl nitriles has been developed. This process is based on the direct reaction of in situ prepared L•Pd(Ar)X complexes (L=biaryl phosphine) with [11C]HCN. The strategy is operationally simple, exhibits a remarkably wide substrate scope with short reaction times, and demonstrates superior reactivity compared to previously reported systems. With this procedure, a variety of [11C]nitrile-containing pharmaceuticals were prepared with high radiochemical efficiency. PMID:25565277

Cooperative dual catalysis: application to the highly enantioselective conjugate cyanation of unsaturated imides.

PubMed

Sammis, Glenn M; Danjo, Hiroshi; Jacobsen, Eric N

2004-08-18

Cooperative heterobimetallic catalysis was used as a design principle to achieve a highly reactive system for the enantioselective conjugate addition of cyanide to alpha,beta-unsaturated imides. A dual-catalyst pathway involving chiral (salen)Al complex 1b and chiral (pybox)Er complex 4b provides measurable improvements in rates and enantioselectivities relative to single-catalyst systems. Mechanistic studies point to a cooperative bimetallic mechanism involving activation of the imide by the Al complex and activation of cyanide by the Er complex.

Filled and Unfilled Temperature-Dependent Epoxy Resin Blends for Lossy Transducer Substrates

PubMed Central

Eames, Matthew D.C.; Hossack, John A.

2016-01-01

In the context of our ongoing investigation of low-cost 2-dimensional (2-D) arrays, we studied the temperature-dependent acoustic properties of epoxy blends that could serve as an acoustically lossy backing material in compact 2-D array-based devices. This material should be capable of being machined during array manufacture, while also providing adequate signal attenuation to mitigate backing block reverberation artifacts. The acoustic impedance and attenuation of 5 unfilled epoxy blends and 2 filled epoxy blends—tungsten and fiberglass fillers—were analyzed across a 35°C temperature range in 5°C increments. Unfilled epoxy materials possessed an approximately linear variation of impedance and sigmoidal variation of attenuation properties over the range of temperatures of interest. An intermediate epoxy blend was fitted to a quadratic trend line with R2 values of 0.94 and 0.99 for attenuation and impedance, respectively. It was observed that a fiberglass filler induces a strong quadratic trend in the impedance data with temperature, which results in increased error in the characterization of attenuation and impedance. The tungsten-filled epoxy was not susceptible to such problems because a different method of fabrication was required. At body temperature, the tungsten-filled epoxy could provide a 44 dB attenuation of the round-trip backing block echo in our application, in which the center frequency is 5 MHz and the backing material is 1.1 mm thick. This is an 11 dB increase in attenuation compared with the fiberglass-filled epoxy in the context of our application. This work provides motivation for exploring the use of custom-made tungsten-filled epoxy materials as a substitute PCB-based substrate to provide electrical signal interconnect. PMID:19406716

Tandem Reactions for Streamlining Synthesis

PubMed Central

HUSSAIN, MAHMUD M.; WALSH, PATRICK J.

2009-01-01

CONSPECTUS In 1980 Sharpless and Katsuki introduced the asymmetric epoxidation of prochiral allylic alcohols (the Sharpless-Katsuki Asymmetric Epoxidation), which enabled the rapid synthesis of highly enantioenriched epoxy alcohols. This reaction was a milestone in the development of asymmetric catalysis because it was the first highly enantioselective oxidation reaction. Furthermore, it provided access to enantioenriched allylic alcohols that are now standard starting materials in natural product synthesis. In 1981 Sharpless and coworkers made another seminal contribution by describing the kinetic resolution (KR) of racemic allylic alcohols. This work demonstrated that small-molecule catalysts could compete with enzymatic catalysts in KRs. For these pioneering works, Sharpless was awarded the 2001 Nobel Prize with Knowles and Noyori. Despite these achievements, the Sharpless KR is not an efficient method to prepare epoxy alcohols with high enantiomeric excess (ee). First, the racemic allylic alcohol must be prepared and purified. KR of the racemic allylic alcohol must be stopped at low conversion, because the ee of the product epoxy alcohol decreases as the KR progresses. Thus, better methods to prepare epoxy alcohols containing stereogenic carbinol carbons are needed. This Account summarizes our efforts to develop one-pot methods for the synthesis of various epoxy alcohols and allylic epoxy alcohols with high enantio-, diastereo-, and chemoselectivity. Our laboratory developed titanium-based catalysts for use in the synthesis of epoxy alcohols with tertiary carbinols. The catalysts are involved in the first step, which is an asymmetric alkyl or allyl addition to enones. The resulting intermediates are then subjected to a titanium-directed diastereoselective epoxidation to provide tertiary epoxy alcohols. Similarly, the synthesis of acyclic epoxy alcohols begins with asymmetric additions to enals and subsequent epoxidation. The methods described here enable the synthesis of skeletally diverse epoxy alcohols. PMID:18710197

Hearing loss in workers exposed to epoxy adhesives and noise: a cross-sectional study

PubMed Central

Yang, Hsiao-Yu; Shie, Ruei-Hao; Chen, Pau-Chung

2016-01-01

Objectives Epoxy adhesives contain organic solvents and are widely used in industry. The hazardous effects of epoxy adhesives remain unclear. The objective of this study was to investigate the risk of hearing loss among workers exposed to epoxy adhesives and noise. Design Cross-sectional study. Methods For this cross-sectional study, we recruited 182 stone workers who were exposed to both epoxy adhesives and noise, 89 stone workers who were exposed to noise only, and 43 workers from the administrative staff who had not been exposed to adhesives or noise. We obtained demographic data, occupational history and medical history through face-to-face interviews and arranged physical examinations and pure-tone audiometric tests. We also conducted walk-through surveys in the stone industry. A total of 40 representative noise assessments were conducted in 15 workplaces. Air sampling was conducted at 40 workplaces, and volatile organic compounds were analysed using the Environmental Protection Agency (EPA) TO-15 method. Results The mean sound pressure level was 87.7 dBA (SD 9.9). The prevalence of noise-induced hearing loss was considerably increased in the stone workers exposed to epoxy adhesives (42%) compared with the stone workers who were not exposed to epoxy adhesives (21%) and the administrative staff group (9.3%). A multivariate logistic regression analysis revealed that exposure to epoxy adhesives significantly increased the risk of hearing loss between 2 and 6 kHz after adjusting for age. Significant interactions between epoxy adhesives and noise and hearing impairment were observed at 3, 4 and 6 kHz. Conclusions Epoxy adhesives exacerbate hearing impairment in noisy environments, with the main impacts occurring in the middle and high frequencies. PMID:26892792

Silane coupling agent for attaching fusion-bonded epoxy to steel.

PubMed

Tchoquessi Diodjo, Madeleine R; Belec, Lénaïk; Aragon, Emmanuel; Joliff, Yoann; Lanarde, Lise; Perrin, François-Xavier

2013-07-24

We describe the possibility of using γ-aminopropyltriethoxysilane (γ-APS) to increase the durability of epoxy powder coating/steel joints. The curing temperature of epoxy powder coatings is frequently above 200 °C, which is seen so far as a major limitation for the use of the heat-sensitive aminosilane coupling agent. Despite this limitation, we demonstrate that aminosilane is a competitive alternative to traditional chromate conversion to enhance the durability of epoxy powder coatings/steel joints. Fourier-transform reflection-absorption infrared spectroscopy (FT-RAIRS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were used to identify the silane deposition conditions that influence the adhesion of epoxy powder coatings on steel. We show that AFM analysis provides highly sensitive measurements of mechanical property development and, as such, the degree of condensation of the silane. The joint durability in water at 60 °C was lower when the pH of the γ-APS solution was controlled at 4.6 using formic acid, rather than that at natural pH (10.6). At the curing temperature of 220 °C, oxidation of the carbon adjacent to the amine headgroup of γ-APS gives amide species by a pseudofirst-order kinetics. However, a few amino functionalities remain to react with oxirane groups of epoxy resin and, thus, strengthen the epoxy/silane interphase. The formation of ammonium formate in the acidic silane inhibits the reaction between silane and epoxy, which consequently decreases the epoxy/silane interphase cohesion. We find that the nanoroughness of silane deposits increases with the cure temperature which is beneficial to the wet stability of the epoxy/steel joints, due to increased mechanical interlocking.

Liquid-Crystal Thermosets, a New Generation of High-Performance Liquid-Crystal Polymers

NASA Technical Reports Server (NTRS)

Dingemans, Theo; Weiser, Erik; Hou, Tan; Jensen, Brian; St. Clair, Terry

2004-01-01

One of the major challenges for NASA's next-generation reusable-launch-vehicle (RLV) program is the design of a cryogenic lightweight composite fuel tank. Potential matrix resin systems need to exhibit a low coefficient of thermal expansion (CTE), good mechanical strength, and excellent barrier properties at cryogenic temperatures under load. In addition, the resin system needs to be processable by a variety of non-autoclavable techniques, such as vacuum-bag curing, resin-transfer molding (RTM), vacuum-assisted resin-transfer molding (VaRTM), resin-film infusion (RFI), pultrusion, and advanced tow placement (ATP). To meet these requirements, the Advanced Materials and Processing Branch (AMPB) at NASA Langley Research Center developed a new family of wholly aromatic liquid-crystal oligomers that can be processed and thermally cross-linked while maintaining their liquid-crystal order. All the monomers were polymerized in the presence of a cross-linkable unit by use of an environmentally benign melt-condensation technique. This method does not require hazardous solvents, and the only side product is acetic acid. The final product can be obtained as a powder or granulate and has an infinite shelf life. The obtained oligomers melt into a nematic phase and do not exhibit isotropization temperatures greater than the temperatures of decomposition (Ti > T(sub dec)). Three aromatic formulations were designed and tested and included esters, ester-amides, and ester-imides. One of the major advantages of this invention, named LaRC-LCR or Langley Research Center-Liquid Crystal Resin, is the ability to control a variety of resin characteristics, such as melting temperature, viscosity, and the cross-link density of the final part. Depending on the formulation, oligomers can be prepared with melt viscosities in the range of 10-10,000 poise (100 rad/s), which can easily be melt-processed using a variety of composite-processing techniques. This capability provides NASA with custom-made matrix resins that meet the required processing conditions for the fabrication of textile composites. Once the resin is in place, the temperature is raised to 375 C and the oligomers are cross-linked into a high-glass-transition-temperature (Tg) nematic network without releasing volatiles. The mechanical properties of the fully crosslinked, composite articles are comparable to typical composites based on commercially available epoxy resins.

Fluorinated Alkyl Ether Epoxy Resin Compositions and Applications Thereof

NASA Technical Reports Server (NTRS)

Connell, John W. (Inventor); Wohl, Christopher J. (Inventor); Siochi, Emilie J. (Inventor); Gardner, John M. (Inventor); Smith, Joseph G. (Inventor); Palmieri, Frank M. (Inventor)

2017-01-01

Epoxy resin compositions prepared using amino terminated fluoro alkyl ethers. The epoxy resin compositions exhibit low surface adhesion properties making them useful as coatings, paints, moldings, adhesives, and fiber reinforced composites.

Physical aging of linear and network epoxy resins

NASA Technical Reports Server (NTRS)

Kong, E. S.-W.; Wilkes, G. L.; Mcgrath, J. E.; Banthia, A. K.; Mohajer, Y.; Tant, M. R.

1981-01-01

Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers are prepared and studied using diamine and anhydride crosslinking agents. Rubber modified epoxies and a carbon fiber reinforced composite are also investigated. All materials display time-dependent changes when stored at temperatures below the glass transition temperature after quenching (sub-T/g/ annealing). Solvent sorption experiments initiated after different sub-T(g) annealing times demonstrate that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. Residual thermal stresses and water are found to have little effect on the physical aging process, which affects the sub-T(g) properties of uniaxial carbon fiber reinforced epoxy material. Finally, the importance of the recovery phenomenon which affects the durability of epoxy glasses is considered.

Effect of Epoxy on Mechanical Property of SAC305 Solder Joint with Various Surface Finishes Under 3-Point Bend Test.

PubMed

Jeong, Haksan; Myung, Woo-Ram; Sung, Yong-Gue; Kim, Kyung-Yeol; Jung, Seung-Boo

2018-09-01

Microstructures and mechanical property of Sn-3.0Ag-0.5Cu (SAC305) and epoxy Sn-3.0Ag-0.5Cu (epoxy SAC) solder joints were investigated with various surface finishes; organic solderability preservative (OSP), electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). Bending property of solder joints was evaluated by 3-point bend test method. Microstructure and chemical composition of solder joints was characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. Epoxy did not effect on intermetallic compound (IMC) morphology. Scalloped shaped Cu6Sn5 IMC was observed at OSP surface finish. Chunky-like shaped and needle-like shaped (Ni,Cu)6Sn5 IMC were observed at the solder/ENIG joint and solder/ENEPIG joint, respectively. The bending cycles of SAC305/OSP joint, SAC305/ENIG joints and SAC305/ENEPIG joints were 720, 440 and 481 cycle numbers. The bending cycles of epoxy SAC and three types surface finished solder joints were over 1000 bending cycles. Under OSP surface finish, bending cycles of epoxy SAC solder was approximately 1.5 times higher than those of SAC305 solder joint. Bending cycles of epoxy SAC solder was over twice times higher than those of SAC305 solder with ENIG and ENEPIG surface finishes. The bending property of epoxy solder joint was enhanced due to epoxy fillet held the solder joint.

EPOXI Mission Press Conference

NASA Image and Video Library

2010-11-18

Jessica Sunshine, EPOXI Deputy Principal Investigator, University of Maryland, far right, discusses imagery sent back from the EPOXI Mission spacecraft during a press conference, Thursday, Nov. 18, 2010, at NASA Headquarters in Washington. The press conference was held to discuss the Nov. 4 successful flyby of Comet Hartley 2 by NASA's EPOXI Mission Spacecraft. Images from the flyby provided scientists the most extensive observations of a comet in history. Photo Credit: (NASA/Paul E. Alers)

Fracture Mechanics of Transverse Cracks and Edge Delamination in Graphite-Epoxy Composite Laminates.

DTIC Science & Technology

1982-03-01

Fracture failure in multi-layer epoxy-based composite laminates seldom begins with breaking of the load-carrying reinforcing fibers. Rather, smeall...often observed sub-laminate fracture mudes in, e.g., glass-epoxy and graph- ite-epoxy composite laminates. Although these matrix-dominated crackings...the uicrostructures of any given fibrous composite , fracture analysis of sub-laminate cracks based on micro leanie [I Is almost Impossible If not

Investigation of the effect of resin material on impact damage to graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Palmer, R. J.

1981-01-01

The results of an experimental program are described which establishes the feasibility and guide lines for resin development. The objective was to identify the basic epoxy neat resin properties that improve low velocity impact resistance and toughness to graphite-epoxy laminates and at the same time maintain useful structural laminate mechanical properties. Materials tests from twenty-three toughened epoxy resin matrix systems are included.

Rubber-Modified Epoxy and Glass Laminates for Application to Naval Ship Structures.

DTIC Science & Technology

1983-09-01

more information. Two generic carboxy terminated butadiene acrylonitrile ( CTBN )-modified epoxy/glass cloth material systems have been characterized...versus Normal Impact Energy of 7781-Z6040/Fl55 .......... .................... 8 4 - Front Surface of CTBN -Modified Epoxy GRP Panel After 60 Impacts at...15 6 - Back Surface of CTBN -Modified Epoxy GRP Panel After 60 Impacts at 206 Foot-Pounds ..... .................. ... 16 7 - Back Surface of

Epoxy/Fluoroether Composites

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Taylor, M. S.

1986-01-01

Composite materials made from unfilled and glass-fiber-reinforced epoxy toughened by copolymerization with elastomeric prepolymers of perfluoroalkyl ether diacyl fluoride (EDAF). Improved properties due to hydrogen bonding between rubber phase and epoxy matrix, plus formation of rubberlike phase domains that molecularly interpenetrate with epoxy matrix. With optimum rubber content, particle size, and particle shape, entire molecular structure reinforced and toughened. Improved composites also show increased failure strength, stiffness, glass-transition temperature, and resistance to water.

A novel hydroxyl epoxy phosphate monomer enhancing the anticorrosive performance of waterborne Graphene/Epoxy coatings

NASA Astrophysics Data System (ADS)

Ding, Jiheng; Rahman, Obaid ur; Peng, Wanjun; Dou, Huimin; Yu, Haibin

2018-01-01

Herein, we report the synthesis of a novel hydroxyl epoxy phosphate monomer (PGHEP) as an efficient dispersant for graphene to enhance the compatibility of the graphene in epoxy resin. Raman spectroscopy, Ultraviolet-visible spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS) studies were confirmed the π-π interactions between PGHEP and graphene. Well-dispersed states of PGHEP functionalized graphene (G) sheets in water were analyzed by transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Further, microstructure of prepared G/waterborne epoxy coatings containing 0.5-1.0 wt.% of PGHEP functionalized G sheets were also observed with the help of SEM and TEM. The PGHEP functionalized G sheets dispersed composite coatings displayed enhanced corrosion resistance compared with pure epoxy resin, these coatings have higher contact angle, lower water absorption as evident from the results of electrochemical impedance spectroscopy (EIS) and salt spray tests. The superior corrosion protection performances of G/epoxy coatings were mainly attributed to the formed passive film from uniformly dispersed PGHEP functionalized G sheets which act as physical barrier on the steel surface. Therefore, this work provides a novel bio-based efficient dispersant for G sheets and an important method for preparing G/waterborne epoxy coatings with superior corrosion resistance properties.

Superior Mechanical Properties of Epoxy Composites Reinforced by 3D Interconnected Graphene Skeleton.

PubMed

Ni, Ya; Chen, Lei; Teng, Kunyue; Shi, Jie; Qian, Xiaoming; Xu, Zhiwei; Tian, Xu; Hu, Chuansheng; Ma, Meijun

2015-06-03

Epoxy-based composites reinforced by three-dimensional graphene skeleton (3DGS) were fabricated in resin transfer molding method with respect to the difficulty in good dispersion and arrangement of graphene sheets in composites by directly mixing graphene and epoxy. 3DGS was synthesized in the process of self-assembly and reduction with poly(amidoamine) dendrimers. In the formation of 3DGS, graphene sheets were in good dispersion and ordered state, which resulted in exceptional mechanical properties and thermal stability for epoxy composites. For 3DGS/epoxy composites, the tensile and compressive strengths significantly increased by 120.9% and 148.3%, respectively, as well as the glass transition temperature, which increased by a notable 19 °C, unlike the thermal exfoliation graphene/epoxy composites via direct-mixing route, which increased by only 0.20 wt % content of fillers. Relative to the graphene/epoxy composites in direct-mixing method mentioned in literature, the increase in tensile and compressive strengths of 3DGS/epoxy composites was at least twofold and sevenfold, respectively. It can be expected that 3DGS, which comes from preforming graphene sheets orderly and dispersedly, would replace graphene nanosheets in polymer nanocomposite reinforcement and endow composites with unique structure and some unexpected performance.

Effect of carbon nanotube dispersion on glass transition in cross-linked epoxy-carbon nanotube nanocomposites: role of interfacial interactions.

PubMed

Khare, Ketan S; Khare, Rajesh

2013-06-20

We have used atomistic molecular simulations to study the effect of nanofiller dispersion on the glass transition behavior of cross-linked epoxy-carbon nanotube (CNT) nanocomposites. Specific chemical interactions at the interface of CNTs and cross-linked epoxy create an interphase region, whose impact on the properties of their nanocomposites increases with an increasing extent of dispersion. To investigate this aspect, we have compared the volumetric, structural, and dynamical properties of three systems: neat cross-linked epoxy, cross-linked epoxy nanocomposite containing dispersed CNTs, and cross-linked epoxy nanocomposite containing aggregated CNTs. We find that the nanocomposite containing dispersed CNTs shows a depression in the glass transition temperature (Tg) by ~66 K as compared to the neat cross-linked epoxy, whereas such a large depression is absent in the nanocomposite containing aggregated CNTs. Our results suggest that the poor interfacial interactions between the CNTs and the cross-linked epoxy matrix lead to a more compressible interphase region between the CNTs and the bulk matrix. An analysis of the resulting dynamic heterogeneity shows that the probability of percolation of immobile domains becomes unity near the Tg calculated from volumetric properties. Our observations also lend support to the conceptual analogy between polymer nanocomposites and the nanoconfinement of polymer thin films.

Development of silane grafted ZnO core shell nanoparticles loaded diglycidyl epoxy nanocomposites film for antimicrobial applications.

PubMed

Suresh, S; Saravanan, P; Jayamoorthy, K; Ananda Kumar, S; Karthikeyan, S

2016-07-01

In this article a series of epoxy nanocomposites film were developed using amine functionalized (ZnO-APTES) core shell nanoparticles as the dispersed phase and a commercially available epoxy resin as the matrix phase. The functional group of the samples was characterized using FT-IR spectra. The most prominent peaks of epoxy resin were found in bare epoxy and in all the functionalized ZnO dispersed epoxy nanocomposites (ZnO-APTES-DGEBA). The XRD analysis of all the samples exhibits considerable shift in 2θ, intensity and d-spacing values but the best and optimum concentration is found to be 3% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposites supported by FT-IR results. From TGA measurements, 100wt% residue is obtained in bare ZnO nanoparticles whereas in ZnO core shell nanoparticles grafted DGEBA residue percentages are 37, 41, 45, 46 and 52% for 0, 1, 3, 5 and 7% ZnO-APTES-DGEBA respectively, which is confirmed with ICP-OES analysis. From antimicrobial activity test, it was notable that antimicrobial activity of 7% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposite film has best inhibition zone effect against all pathogens under study. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of epoxy resin sealing on corrosion resistance of arc spraying aluminium coating using cathode electrophoresis method

NASA Astrophysics Data System (ADS)

Pang, Xuming; Wang, Runqiu; Wei, Qian; Zhou, Jianxin

2018-01-01

Arc-sprayed Al coating was sealed with epoxy resin using the cathode electrophoresis method. The anti-corrosion performance of the coatings sealed with epoxy resin was studied by means of a 3.5 wt.% NaCl solution test at 40 °C. For comparison, the anti-corrosion performance of Al coating sealed with boiling water was also performed under the same conditions. The results show that epoxy resin with a thickness of about 20 microns can entirely cover open pores and decreases the surface roughness of the as-sprayed Al coating, and the epoxy resin even permeates into the gaps among lamellar splats from open pores. After corrosion, the thickness of the epoxy resin layer is unchanged and can still cover the as-sprayed Al coating entirely. However, the thickness of Al coating sealed with boiling water decreases from 100 to 40 microns, which indicates that the arc-sprayed Al coating has much better corrosion resistance than the Al coating sealed with boiling water. Meanwhile, the content of substituted benzene ring in the epoxy resin increases, but aromatic ring decreases according to the fourier transform infrared spectra, which will cause the rigidity of the epoxy resin to increase, but the toughness slightly decreases after corrosion.

A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts.

PubMed

Wang, Yiru; Liu, Wanshuang; Qiu, Yiping; Wei, Yi

2018-04-27

Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high T g parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles.

A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts

PubMed Central

Wang, Yiru; Qiu, Yiping; Wei, Yi

2018-01-01

Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high Tg parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles. PMID:29702575

Effects of colloidal nanosilica on the rheological properties of epoxy resins filled with organoclay.

PubMed

Nguyen, Dinh Huong; Song, Gwang Seok; Lee, Dai Soo

2011-05-01

The rheological properties of epoxy resins filled with organoclay and colloidal nanosilica were investigated by employing a parallel plate rheometer in flow mode at 25 degrees C. Shear thickening and shear thinning behaviors were observed in the epoxy resins filled with a mixture of organoclay and colloidal nanosilica. Minima were observed in the relaxation time of the systems consisting of epoxy resins filled with organoclay and colloidal silica as the content of colloidal nanosilica was increased. It seems that the colloidal nanosilica increased the mobility of the filled epoxy resins and reduced the interactions between the silicate layers in the systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gantayat, S., E-mail: subhra-gantayat@rediffmail.com; Rout, D.; Swain, S. K.

The effect of the functionalization of multiwalled carbon nanotube on the structure and electrical properties of composites was investigated. Samples based on epoxy resin with different weight percentage of MWCNTs were prepared and characterized. The interaction between MWCNT & epoxy resin was noticed by Fourier transform infrared spectroscopy (FTIR). The structure of functionalized multiwalled carbon nanotube (f-MWCNT) reinforced epoxy composite was studied by field emission scanning electron microscope (FESEM). The dispersion of f-MWCNT in epoxy resin was evidenced by high resolution transmission electron microscope (HRTEM). Electrical properties of epoxy/f-MWCNT nanocomposites were measured & the result indicated that the conductivity increasedmore » with increasing concentration of f-MWCNTs.« less

Postbuckling behavior of graphite-epoxy panels

NASA Technical Reports Server (NTRS)

Starnes, J. H., Jr.; Dickson, J. N.; Rouse, M.

1984-01-01

Structurally efficient fuselage panels are often designed to allow buckling to occur at applied loads below ultimate. Interest in applying graphite-epoxy materials to fuselage primary structure led to several studies of the post-buckling behavior of graphite-epoxy structural components. Studies of the postbuckling behavior of flat and curved, unstiffened and stiffened graphite-epoxy panels loaded in compression and shear were summarized. The response and failure characteristics of specimens studied experimentally were described, and analytical and experimental results were compared. The specimens tested in the studies described were fabricated from commercially available 0.005-inch-thick unidirectional graphite-fiber tapes preimpregnated with 350 F cure thermosetting epoxy resins.

Electron and proton absorption calculations for a graphite/epoxy composite model. [large space structures

NASA Technical Reports Server (NTRS)

Long, E. R., Jr.

1979-01-01

The Bethe-Bloch stopping power relations for inelastic collisions were used to determine the absorption of electron and proton energy in cured neat epoxy resin and the absorption of electron energy in a graphite/epoxy composite. Absorption of electron energy due to bremsstrahlung was determined. Electron energies from 0.2 to 4.0 MeV and proton energies from 0.3 to 1.75 MeV were used. Monoenergetic electron energy absorption profiles for models of pure graphite, cured neat epoxy resin, and graphite/epoxy composites are reported. A relation is determined for depth of uniform energy absorption in a composite as a function of fiber volume fraction and initial electron energy. Monoenergetic proton energy absorption profiles are reported for the neat resin model. A relation for total proton penetration in the epoxy resin as a function of initial proton energy is determined. Electron energy absorption in the composite due to bremsstrahlung is reported. Electron and proton energy absorption profiles in cured neat epoxy resin are reported for environments approximating geosynchronous earth orbit.

Fast Fourier Transform IR Characterization of Epoxy GY Systems Crosslinked with Aliphatic and Cycloaliphatic EH Polyamine Adducts

PubMed Central

Nikolic, Goran; Zlatkovic, Sasa; Cakic, Milorad; Cakic, Suzana; Lacnjevac, Caslav; Rajic, Zoran

2010-01-01

The use of fast FT-IR spectroscopy as a sensitive method to estimate a change of the crosslinking kinetics of epoxy resin with polyamine adducts is described in this study. A new epoxy formulation based on the use of polyamine adducts as the hardeners was analyzed. Crosslinking reactions of the different stoichiometric mixtures of the unmodified GY250 epoxy resin with the aliphatic EH606 and the cycloaliphatic EH637 polyamine adducts were studied using mid FT-IR spectroscopic techniques. As the crosslinking proceeded, the primary amine groups in polyamine adduct are converted to secondary and the tertiary amines. The decrease in the IR band intensity of epoxy groups at about 915 cm−1, as well as at about 3,056 cm−1, was observed due to process. Mid IR spectral analysis was used to calculate the content of the epoxy groups as a function of crosslinking time and the crosslinking degree of resin. The amount of all the epoxy species was estimated from IR spectra to changes during the crosslinking kinetics of epichlorhydrin. PMID:22315562

Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites

PubMed Central

Alajmi, Mahdi; Shalwan, Abdullah

2015-01-01

The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR) and coefficient of friction (COF) of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs), as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites. PMID:28793431

Exploratory Study on the Effects of Novel Diamine Curing Agents and Isocyanate Precursors on the Properties of New Epoxy and Urethane Adhesives

NASA Technical Reports Server (NTRS)

Glasgow, D. Gerald; Garthwait, Clayborn

1977-01-01

This report covers the results of investigations directed toward studying the effects of novel aromatic diamine structures on epoxy adhesive properties and includes work done under a modification to the original contract. Three aromatic diamines based on diphenylsulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m'-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m'-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p'-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m'-methylene dianiline-cured epoxy appeared to be equivalent to the p,p'-methylene dianiline-cured epoxy as judged by short beam shear tests.

AC electrical breakdown phenomena of epoxy/layered silicate nanocomposite in needle-plate electrodes.

PubMed

Park, Jae-Jun; Lee, Jae-Young

2013-05-01

Epoxy/layered silicate nanocomposite for the insulation of heavy electric equipments were prepared by dispersing 1 wt% of a layered silicate into an epoxy matrix with a homogenizing mixer and then AC electrical treeing and breakdown tests were carried out. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that nano-sized monolayers were exfoliated from a multilayered silicate in the epoxy matrix. When the nano-sized silicate layers were incorporated into the epoxy matrix, the breakdown rate in needle-plate electrode geometry was 10.6 times lowered than that of the neat epoxy resin under the applied electrical field of 520.9 kV/mm at 30 degrees C, and electrical tree propagated with much more branches in the epoxy/layered silicate nanocomposite. These results showed that well-dispersed nano-sized silicate layers retarded the electrical tree growth rate. The effects of applied voltage and ambient temperature on the tree initiation, growth, and breakdown rate were also studied, and it was found that the breakdown rate was largely increased, as the applied voltage and ambient temperature increased.

Correlation between Mechanical Properties with Specific Wear Rate and the Coefficient of Friction of Graphite/Epoxy Composites.

PubMed

Alajmi, Mahdi; Shalwan, Abdullah

2015-07-08

The correlation between the mechanical properties of Fillers/Epoxy composites and their tribological behavior was investigated. Tensile, hardness, wear, and friction tests were conducted for Neat Epoxy (NE), Graphite/Epoxy composites (GE), and Data Palm Fiber/Epoxy with or without Graphite composites (GFE and FE). The correlation was made between the tensile strength, the modulus of elasticity, elongation at the break, and the hardness, as an individual or a combined factor, with the specific wear rate (SWR) and coefficient of friction (COF) of composites. In general, graphite as an additive to polymeric composite has had an eclectic effect on mechanical properties, whereas it has led to a positive effect on tribological properties, whilst date palm fibers (DPFs), as reinforcement for polymeric composite, promoted a mechanical performance with a slight improvement to the tribological performance. Statistically, this study reveals that there is no strong confirmation of any marked correlation between the mechanical and the specific wear rate of filler/Epoxy composites. There is, however, a remarkable correlation between the mechanical properties and the friction coefficient of filler/Epoxy composites.

Deposition of SiC x H y O z thin film on epoxy resin by nanosecond pulsed APPJ for improving the surface insulating performance

NASA Astrophysics Data System (ADS)

Qing, XIE; Haofan, LIN; Shuai, ZHANG; Ruixue, WANG; Fei, KONG; Tao, SHAO

2018-02-01

Non-thermal plasma surface modification for epoxy resin (EP) to improve the insulation properties has wide application prospects in gas insulated switchgear and gas insulated transmission line. In this paper, a pulsed Ar dual dielectrics atmospheric-pressure plasma jet (APPJ) was used for SiC x H y O z thin film deposition on EP samples. The film deposition was optimized by varying the treatment time while other parameters were kept at constants (treatment distance: 10 mm, precursor flow rate: 0.6 l min-1, maximum instantaneous power: 3.08 kW and single pulse energy: 0.18 mJ). It was found that the maximum value of flashover voltages for negative and positive voltage were improved by 18% and 13% when the deposition time was 3 min, respectively. The flashover voltage reduced as treatment time increased. Moreover, all the surface conductivity, surface charge dissipation rate and surface trap level distribution reached an optimal value when thin film deposition time was 3 min. Other measurements, such as atomic force microscopy and scanning electron microscope for EP surface morphology, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy for EP surface compositions, optical emission spectra for APPJ deposition process were carried out to better understand the deposition processes and mechanisms. The results indicated that the original organic groups (C-H, C-C, C=O, C=C) were gradually replaced by the Si containing inorganic groups (Si-O-Si and Si-OH). The reduction of C=O in ester group and C=C in p-substituted benzene of the EP samples might be responsible for shallowing the trap level and then enhancing the flashover voltage. However, when the plasma treatment time was longer than 3 min, the significant increase of the surface roughness might increase the trap level depth and then deteriorate the flashover performance.

Epoxy coated reinforcement study : final report.

DOT National Transportation Integrated Search

1999-06-01

This report evaluates the use of Scotchlite 213 epoxy coated reinforcement in Oregon coastal environments. There is an extensive body of knowledge documenting epoxy coated reinforcement research in North America in the last 20 years. The research has...

High Strain Rate Mechanical Properties of Epoxy and Epoxy-Based Particulate Composites

DTIC Science & Technology

2007-08-01

and titanium alloy (Ti- 6Al - 4V ) bar materials available. For all bar systems, the properties of the sample are determined by measuring the...polished, carbon-coated specimens provided adequate contrast between the aluminum particles, the epoxy matrix and any porosity present after curing...difference between the two measures of particle size can be explained by the higher levels of porosity observed in the Epoxy-65H2 specimen, which

Compression of Composite Materials: A Review,

DTIC Science & Technology

1987-11-01

epoxy tension face, . and a plexiglass core under the specimen gage-section. A Kevlar /glass phenolic hybrid composite system was evaluated in the...epoxy [0116 specimens, S2/SP-250 7 glass/epoxy [0/±45/9012s specimens, Kevlar 285 weave/Cycom 4143 Aramid/epoxy specimens, unidirectional FP alumina...bundles tested erc- E-glass, T300 graphite, T700 graphite, P75 graphite, Kevlar 49, and FP alumina. " -1. They observed that bundle failure

Use of 2,5-dimethyl-2,5-hexane diamine as a curing agent for epoxy resins. [Patent application

DOEpatents

Rinde, J.A.; Newey, H.A.

Primary diamines are prepared for use as a curing agent for epoxy resins. These curing agents can be used to form epoxy resin mixtures useful in filament winding and preimpregnated fiber molding and in formulating film adhesives, powder coatings and molding powders. The epoxy mixtures form for such uses a room temperature non-reacting, intermediate stable state which has a latent cross-linking capability.

Synthesis and Structure Property Studies of Toughened Epoxy Resins Via Functionalized Polysiloxanes.

DTIC Science & Technology

1987-09-30

34 87S N4 SYNTHESIS RNO STRUCTURE PROPERTY STUDIES OF OP NDD mEPOXY RESINS YIN FU.. (U) VIROINIR POLYTECHNIC INST OM STNTE UNIY RCKSBURG DEPT OF C.. J...Classification) Synthesis and Structure Property Studies of Toughened Epoxy Resins Via Functionalized Polysiloxanes 12. PERSONALAUTHOR(S) J. 5. HitTIe... Resins , Toughening 19. ABSTRACT (Continue on reverse if necessary and identify by block number) Epoxy resins chemically modified with functionally

Microencapsulation of Polyfunctional Amines for Self-Healing of Epoxy-Based Composites

DTIC Science & Technology

2008-01-01

MICROENCAPSULATION OF POLYFUNCTIONAL AMINES FOR SELF-HEALING OF EPOXY-BASED COMPOSITES David A. McIlroy*§, Ben J. Blaiszik,¥ Paul V. Braun... microcapsules containing an amine hardener (DEH-52, Dow Chemical) for use as the hardener in a 2-part epoxy healing system consisting of epoxy...microscope. Scanning electron microscopy was performed on a Philips XL30 ESEM-FEG instrument. Microencapsulation Procedure. 10 g of a 2:1 v/v

Evaluation of the Epoxy/Antimony Trioxide Nanocomposites as Flame Retardant

NASA Astrophysics Data System (ADS)

Dheyaa, Balqees M.; Jassim, Widad H.; Hameed, Noor A.

2018-05-01

Antimony trioxide nanopowder was added for epoxy resin in various amount weight percentages (0, 2, 4, 6, 8, and 10) wt% to increase the combustion resistance and decrease the flammability for it. The study included three standard tests used to measure: limiting oxygen index (LOI), rate of burning (R.B), burning extent (E.B), burning time (T.B), maximum flame height (H) and residue percentage after burning in order to determine the effectiveness of the used additives to decrease the flammability of epoxy resin and increase the combustion resistance. Thermal test was done by using Lee’s disk to measure the thermal conductivity coefficient. The thermal stability and degradation kinetics of epoxy resin without reinforcement and with reinforcement by (10 wt%) were studied by using thermogravimetric analysis (TGA). The recorded results indicated that epoxy reinforced by (10 wt%) has a good effect as flame retardants for epoxy resin and active to inhibit burning and reduce the flammability.

Biobased Epoxy Resins from Deconstructed Native Softwood Lignin.

PubMed

van de Pas, Daniel J; Torr, Kirk M

2017-08-14

The synthesis of novel epoxy resins from lignin hydrogenolysis products is reported. Native lignin in pine wood was depolymerized by mild hydrogenolysis to give an oil product that was reacted with epichlorohydrin to give epoxy prepolymers. These were blended with bisphenol A diglycidyl ether or glycerol diglycidyl ether and cured with diethylenetriamine or isophorone diamine. The key novelty of this work lies in using the inherent properties of the native lignin in preparing new biobased epoxy resins. The lignin-derived epoxy prepolymers could be used to replace 25-75% of the bisphenol A diglycidyl ether equivalent, leading to increases of up to 52% in the flexural modulus and up to 38% in the flexural strength. Improvements in the flexural strength were attributed to the oligomeric products present in the lignin hydrogenolysis oil. These results indicate lignin hydrogenolysis products have potential as sustainable biobased polyols in the synthesis of high performance epoxy resins.

Quantitative characterization of solid epoxy resins using comprehensive two dimensional liquid chromatography coupled with electrospray ionization-time of flight mass spectrometry.

PubMed

Julka, Samir; Cortes, Hernan; Harfmann, Robert; Bell, Bruce; Schweizer-Theobaldt, Andreas; Pursch, Matthias; Mondello, Luigi; Maynard, Shawn; West, David

2009-06-01

A comprehensive multidimensional liquid chromatography system coupled to Electrospray Ionization-Mass Spectrometry (LCxLC-ESI-MS) was developed for detailed characterization and quantitation of solid epoxy resin components. The two orthogonal modes of separation selected were size exclusion chromatography (SEC) in the first dimension and liquid chromatography at critical conditions (LCCC) in the second dimension. Different components present in the solid epoxy resins were separated and quantitated for the first time based on the functional groups and molecular weight heterogeneity. Coupling LCxLC separations with mass spectrometry enabled the identification of components resolved in the two-dimensional space. Several different functional group families of compounds were separated and identified, including epoxy-epoxy and epoxy-alpha-glycol functional oligomers, and their individual molecular weight ranges were determined. Repeatability obtained ranged from 0.5% for the main product to 21% for oligomers at the 0.4% concentration level.

Characterization of Epoxy Functionalized Graphite Nanoparticles and the Physical Properties of Epoxy Matrix Nanocomposites

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Bauer, Jonathan L.; Maryanski, Michael J.; Heimann, Paula J.; Barlow, Jeremy P.; Gosau, Jan-Michael; Allred, Ronald E.

2010-01-01

This work presents a novel approach to the functionalization of graphite nanoparticles. The technique provides a mechanism for covalent bonding between the filler and matrix, with minimal disruption to the sp2 hybridization of the pristine graphene sheet. Functionalization proceeded by covalently bonding an epoxy monomer to the surface of expanded graphite, via a coupling agent, such that the epoxy concentration was measured as approximately 4 wt.%. The impact of dispersing this material into an epoxy resin was evaluated with respect to the mechanical properties and electrical conductivity of the graphite-epoxy nanocomposite. At a loading as low as 0.5 wt.%, the electrical conductivity was increased by five orders of magnitude relative to the base resin. The material yield strength was increased by 30% and Young s modulus by 50%. These results were realized without compromise to the resin toughness.

Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

NASA Astrophysics Data System (ADS)

Adak, Nitai Chandra; Chhetri, Suman; Kim, Nam Hoon; Murmu, Naresh Chandra; Samanta, Pranab; Kuila, Tapas

2018-03-01

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young's modulus, toughness, flexural strength and flexural modulus by 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tan δ), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis.

Friction and Wear Behavior of Carbon Fabric-Reinforced Epoxy Composites

NASA Astrophysics Data System (ADS)

Şahin, Y.; De Baets, Patrick

2017-12-01

Besides intrinsic material properties, weight/energy savings and wear performance play an important role in the selection of materials for any engineering application. The tribological behavior of carbon fabric-reinforced epoxy composites produced by molding technique was investigated using a reciprocating pin-on-plate configuration. It was shown that the wear rate considerably decreased (by a factor of approx. 8) with the introduction of the reinforcing carbon fabric into the epoxy matrix. It was observed that the wear rate of the tested composites increased with an increase in normal load. Moreover, the coefficient of friction for epoxy/steel and composites/steel tribo-pairs was also determined and decreased with increasing load. By means of scanning electron microscopy of the wear tracks, different wear mechanisms such as matrix wear, matrix fatigue and cracking, matrix debris formation for neat epoxy together with fabric/fiber thinning, fabric breakage and fabric/matrix debonding for the reinforced epoxy could be distinguished.

Nanoindentation study of interphases in epoxy/amine thermosetting systems modified with thermoplastics.

PubMed

Ramos, Jose Angel; Blanco, Miren; Zalakain, Iñaki; Mondragon, Iñaki

2009-08-15

The characterization of a mixture of epoxy/amine with different stoichiometric ratios was carried out by means of nanoindentation. The epoxy system was composed by diglycidyl ether of bisphenol-A and 4,4'-methylene bis-(3-chloro 2,6-diethylaniline). Diffusion through interface formed by epoxy/amine system in stoichiometric ratio and several thermoplastic polymers was also analyzed by means of stiffness analysis, as studied by atomic force microscopy (AFM) and coupled nanoindentation tests. Used thermoplastics were an amorphous, atactic polystyrene, and two semicrystalline, syndiotactic polystyrene and poly(phenylene sulfide). Larger range diffusion was obtained in epoxy/amine systems modified with atactic polystyrene while the study of the influence of stoichiometric ratio suggests that the excess of epoxy generated stiffer material. In addition, larger indentation loads resulted in higher apparent stiffness because of the more number of polymer chains that had to re-accommodate owing to the increase in contact area.

Dynamic stress analysis of smooth and notched fiber composite flexural specimens

NASA Technical Reports Server (NTRS)

Murthy, P. L. N.; Chamis, C. C.

1984-01-01

A detailed analysis of the dynamic stress field in smooth and notched fiber composite (Charpy-type) specimens is reported in this paper. The analysis is performed with the aid of the direct transient response analysis solution sequence of MSC/NASTRAN. Three unidirectional composites were chosen for the study. They are S-Glass/Epoxy, Kevlar/Epoxy and T-300/Epoxy composite systems. The specimens are subjected to an impact load which is modeled as a triangular impulse with a maximum of 2000 lb and a duration of 1 ms. The results are compared with those of static analysis of the specimens subjected to a peak load of 2000 lb. For the geometry and type of materials studied, the static analysis results gave close conservative estimates for the dynamic stresses. Another interesting inference from the study is that the impact induced effects are felt by S-Glass/Epoxy specimens sooner than Kevlar/Epoxy or T-300/Epoxy specimens.

Modified Epoxy Composites

NASA Technical Reports Server (NTRS)

Gilwee, W. J.

1984-01-01

The properties of a rubber-modified experimental epoxy resin and a standard epoxy as composite matrices were studied. In addition, a brominated epoxy resin was used in varying quantities to improve the fire resistance of the composite. The experimental resin was tris-(hydroxyphenyl)methane triglycidyl ether, known as tris epoxy novolac (TEN). The standard epoxy resin used was tetraglycidyl 4,4'-diaminodiphenyl methane (TGDDM). The above resins were modified with carboxyl-terminated butadiene acrylonitrile (CTBN) rubber. It is concluded that: (1) modification of TEN resin with bromine gives better impact resistance than rubber modification alone; (2) 25% rubber addition is necessary to obtain significant improvement in impact resistance; (3) impact resistance increases with bromine content; (4) impact velocity does not significantly affect the energy absorbed by the test sample; (5) Tg did not decline with rubber modification; and (6) TEN resin had better hot/wet properties than TGDDM resin.

Cationic cure kinetics of a polyoxometalate loaded epoxy nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Benjamin J.

2012-08-06

The reaction cure kinetics of a novel polyoxometalate (POM) loaded epoxy nanocomposite is described. The POM is dispersed in the epoxy resin up to volume fractions of 0.1. Differential scanning calorimetry measurements show the cure of the epoxy resin to be sensitive to the POM loading. A kinetics study of the cure exotherm confirms that POM acts as a catalyst promoting cationic homopolymerization of the epoxy resin. The cure reaction is shown to propagate through two cure regimes. A fast cure at short time is shown to be propagation by the activated chain end (ACE) mechanism. A slow cure atmore » long time is shown to be propagation by the activated monomer (AM) mechanism. The activation energies for the fast and slow cure regimes agree well with other epoxy based systems that have been confirmed to propagate by the ACE and AM mechanisms.« less

Fiber-Reinforced Reactive Nano-Epoxy Composites

NASA Technical Reports Server (NTRS)

Zhong, Wei-Hong

2011-01-01

An ultra-high-molecular-weight polyethylene/ matrix interface based on the fabrication of a reactive nano-epoxy matrix with lower surface energy has been improved. Enhanced mechanical properties versus pure epoxy on a three-point bend test include: strength (25 percent), modulus (20 percent), and toughness (30 percent). Increased thermal properties include higher Tg (glass transition temperature) and stable CTE (coefficient of thermal expansion). Improved processability for manufacturing composites includes faster wetting rates on macro-fiber surfaces, lower viscosity, better resin infusion rates, and improved rheological properties. Improved interfacial adhesion properties with Spectra fibers by pullout tests include initial debonding force of 35 percent, a maximum pullout force of 25 percent, and energy to debond at 65 percent. Improved mechanical properties of Spectra fiber composites (tensile) aging resistance properties include hygrothermal effects. With this innovation, high-performance composites have been created, including carbon fibers/nano-epoxy, glass fibers/nano-epoxy, aramid fibers/ nano-epoxy, and ultra-high-molecularweight polyethylene fiber (UHMWPE).

Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties on new epoxy and urethane adhesives

NASA Technical Reports Server (NTRS)

Glasgow, D. G.; Garthwait, C.

1977-01-01

Aromatic diamines based on diphenyl sulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m prime-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m prime-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p prime-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m prime-methylene dianiline-cured epoxy appeared to be equivalent to the p,p prime-methylene dianiline-cured epoxy as judged by short beam shear tests.