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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Application of In Situ Fiberization for fabrication of improved strain isolation pads and graphite epoxy composites

The feasibility of applying the in situ fiberization process to the fabrication of strain isolation pads (SIP) for the Space Shuttle and to the fabrication of graphite-epoxy composites was evaluated. The ISF process involves the formation of interconnected polymer fiber networks by agitation of dilute polymer solutions under controlled conditions. High temperature polymers suitable for SIP use were fiberized and a successful fiberization of polychloro trifluoroethylene, a relatively high melting polymer, was achieved. Attempts to fiberize polymers with greater thermal stability were unsuccessful, apparently due to characteristics caused by the presence of aromaticity in the backbone of such materials. Graphite-epoxy composites were fabricated by interconnecting two dimensional arrays of graphite fiber with polypropylene IS fibers with subsequent epoxy resin impregnation. Mechanical property tests were performed on laminated panels of this material to evaluate intralaminar and interlaminar shear strength, and thus fracture toughness. Test results were generally unpromising.

Rosser, R. W.↗
NASA NTRS1981

Infrared spectroscopic analysis of the effects of simulated space radiation on a polyimide

Infrared spectroscopic techniques have been used to study the effects of electron radiation on the polyimide PMDA-p,p-prime- ODA. The radiation exposures were made at various dose rates, for a total dose approximately equal to that for 30 years of exposure to electron radiation in geosynchronous earth orbit. At high dose rates the major effect was probably the formation of a polyisoimide or a charged quaternary amine, and at the low dose rates the effect was a reduction in the amount or aromatic ether linkage. In addition, the effects of dose rate for a small total dose were studied. Elevated temperatures occurred at high dose rates and were, in part, probably the cause of the radiation product. The data suggest that dose rates for accelerated simulations of the space environment should not exceed 100,000 rads/sec.

Ferl, J. E.↗
NASA NTRS1981

Mutagens and carcinogens - Occurrence and role during chemical and biological evolution

The roles of mutagenic and carcinogenic substances in early biologic evolution is examined, along with terrestrial and extraterrestrial sources of mutagens and carcinogens. UV solar radiation is noted to have served to stimulate prebiotic life while also causing harmful effects in plants and animals. Aromatic compounds have been found in meteorites, and comprise leukemogens, polycyclic hydrocarbons, and nitrasamine precursors. Other mutagenic sources are volcanoes, and the beginning of evolution with mutagenic substances is complicated by the appearance of malignancies due to the presence of carcinogens. The atmosphere of the Precambrian period contained both mutagens and early carcinogens and, combined with volcanic activity discharges, formed an atmospheric chemical background analogous to the background ionizing radiation. Carcinogenesis is concluded to be intrinsic to nature, having initiated evolution and, eventually, cancer cells.

Giner-Sorolla, A.↗
NASA NTRS1981

Gravity, lignification, and land plant evolution

Vascular plants began their occupation of the wetlands interfacing both terrestrial and marine environments at some point in early Paleozoic time. Chemical differences between green algae and vascular land plants are mainly related to an abundance of lignins in the land plants. Answers to questions relating to the phylogeny and adaptive significance of the lignins must depend on experiments and observations using contemporary plant material. A summary is provided of a series of such observations. It is found that the differences between modern Chlorophyta and vascular land plants cannot be explained in full on the basis of lignification alone. Nevertheless, the data point to the emergence of the primitive land populations into an oxygen-rich terrestrial world where the need for mechanical support and water conservation could be met by a single aerobic biochemical process connected to essential aromatic amino acids likely to be found in every cell

Siegel, S. M.↗
NASA NTRS1982

Pyrolysis of Precambrian kerogens - Constraints and capabilities

Precambrian kerogens are currently considered to be the primary candidates for the search of biochemical fossils. Degradation of kerogens by relatively 'mild' pyrolysis techniques, such as under high vacuum, can liberate indicative structural moieties which were incorporated in, and perhaps shielded by, these solid and highly condensed, basically aromatic substances. It is necessary to observe analytical constraints (sample size and shape, temperature, pressure, time, etc.) in order to prevent an overabundant yield of secondary pyrolyzates (inter- and intramolecular rearrangements) which can prevent kerogen characterization. Potential biochemical fossils have been found in Precambrian kerogens. Demonstratable syngenetic biochemical fossils are expected after kerogen diagenesis and catagenesis is understood in sufficient detail, and when pyrolysis is augmented by multiple, improved analytical techniques.

Nagy, B.↗
NASA NTRS1982

Polymer research at NASA Langley Research Center

Polymer synthesis programs involve the development of Novel thermoplastics, pseudothermoplastics, and thermosets. These systems are prepared to elucidate structure-property relationships involving thermal capabilities, toughness, processability and environmental stability. Easily processable polyimides, solvent-resistant polysulfones and polyphenylquinoxalines, and tougher high and intermediate temperature polymers were developed. Characterization efforts included high pressure liquid chromatography methodology, the development of toughness tests for fiber reinforced composites, a study of electrical properties of metal ion filled polyimides, and a study of the mutagenicity of aromatic diamines. Also the mechanism of cure/degradation of experimental polymers was studied by rheology, mechanical behavior, separation techniques and spectroscopy. The degradative crosslinking of alkyl-containing polyimides, the separation and identification of crosslinked phenylquinoxalines, the rheological behavior of hot-melt polyimides, and the elucidation of the cure of norbornene endcapped imides were also studied.

Terry L. St. Clair↗
NASA NTRS1983

The development of aerospace polyimide adhesives

Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.

St.clair, A. K.↗
NASA NTRS1983

Mutagenic screening of diamine monomers

The effects of phenyl ring coupling moieties, of isomeric amine positions relative to the coupling groups, and of insertion of other coupling groups on the mutagenic response of a series of dianilines were investigated using the Ames Salmonella assay. Generally, S-9 metabolic activation from Aroclor-induced rat liver was required for mutagenic expression. The range of mutagenicity of steric isomers of several dianiline series was also investigated. No mutagenicity was found for purified samples of o,o' and m,p' isomers of methylene dianiline (MDA) and diaminobenzophenone, while varying degrees of mutagenicity were found for other isomers. The mutagenicity of "benzylogs" of MDA decreased as the degree of linear separation of the m,m' anilino groups by aromatic rings increased. Methylation and two-year storage increased mutagenic response in certain isomers of MDA. However, high performance liquid chromatography indicated there was no discernible change in m,p'-MDA samples aged under varied conditions over four months. Likewise, no change in mutagenicity was found.

Ross, W. D.↗
NASA NTRS1983

Analytical fuel property effects, small combustors, phase 1

The effects of nonstandard aviation fuels on a typical small gas turbine combustor was analyzed. The T700/CT7 engine family was chosen as being representative of the class of aircraft power plants desired. Fuel properties, as specified by NASA, are characterized by low hydrogen content and high aromatics levels. Higher than normal smoke output and flame radiation intensity for the current T700 combustor which serves as a baseline were anticipated. It is, therefore, predicted that out of specification smoke visibility and higher than normal shell temperatures will exist when using NASA ERBS fuels with a consequence of severe reduction in cyclic life. Three new designs are proposed to compensate for the deficiencies expected with the existing design. They have emerged as the best of the eight originally proposed redesigns or combinations thereof. After the five choices that were originally made by NASA on the basis of competing performance factors, General Electric narrowed the field to the three proposed.

Cohen, J. D.↗
NASA NTRS1983

Ultrasonic mixing of epoxy curing agents

A new technique for mixing solid curing agents into liquid epoxy resins using ultrasonic energy was developed. This procedure allows standard curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents with very high melt temperatures such as 4,4 prime-diaminobenzophenone (4,4 prime-DABP) (242 C) to be mixed without premature curing. Four aromatic diamines were ultrasonically blended into MY-720 epoxy resin. These were 4,4 prime-DDS; 3,3 prime-DDA; 4,4 prime-DABP and 3,3 prime-DABP. Unfilled moldings were cast and cured for each system and their physical and mechanical properties compared.

Hodges, W. T.↗
NASA NTRS1980

Method for milling and drilling glass

A process for machining glass by placing a rotating carbide working surface under minimum pressure against an area of glass to be worked is described. Concurrently the region between the working surface and the area of glass is wet with a lubricant consisting essentially of a petroleum carrier, a complex mixture of esters and a complex mixture of naturally occurring aromatic oils.

Rice, S. H.↗
NASA NTRS1983

Development of phosphorylated adhesives

The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame.

Bilow, N.↗
NASA NTRS1982

Method of neutralizing the corrosive surface of amine-cured epoxy resins

The corrosive alkaline surface layer of an epoxy resin product formed by the curing of the epoxy with an aliphatic amine is eliminated by first applying a non-solvent to remove most or all of the free unreacted amine and then applying a layer of a chemical reagent to neutralize the unused amine or amine functional groups by forming a substituted urea. The surface then may be rinsed with acetone and then with alcohol. The non-solvent may be an alcohol. The neutralizing chemical reagent is a mono-isocyanate or a mono-isothiocyanate. Preferred is an aromatic mono-isocyanate such as phenyl isocyanate, nitrophenyl isocyanate and naplthyl isocyanate.

Lee, S. Y.↗
NASA NTRS1983

Polyaryl ethers and related polysiloxane copolymer molecular coatings preparation and radiation degrdation

Poly(arylene ether sulfones) comprise a class of materials known as engineering thermoplastics which have a variety of important applications. These polymers are tough, rigid materials with good mechanical properties over a wide temperature range, and they are processed by conventional methods into products typically having excellent hydrolytic, thermal, oxidative and dimensional stability. Wholly aromatic random copolymers of hydroquinone and biphenol with 4.4 prime dichlorodiphenyl sulfone were synthesized via mechanical nucleophilic displacement. Their structures were characterized and mechanical behavior studied. These tough, ductile copolymers show excellent radiation resistance to electron beam treatment and retain much of the mechanical properties up to at least 700 Mrads under argon.

Mcgrath, J. E.↗
NASA NTRS1982

Tests of blending and correlation of distillate fuel properties

The development of a fuel test matrix, results from tests of several blends of distillate aircraft fuels, and the use of correlations in formulation determination during a NASA-sponsored program to identify new aircraft fuels are described. The program was initiated in order to characterize fuel blends which are appropriate for different types of combustors in use and under development. The fuels were required to feature a specified range of properties. Attention is given to fuel volatility, hydrogen content, aromatic content, freezing point, kinematic viscosity, and naphthalene content. Paraffinic and naphtenic base stocks were employed, using alkyl benzene, naphthene benzenes, and naphthalenes to adjust the blend properties. Categories for the test fuels comprised source-controlled and composition controlled fuels. Test results and compositions of various fuels are provided.

Erwin, J.↗
NASA NTRS1982

The outer satellites of Jupiter

Photometry and spectrophotometry of the Jovian outer satellites are used to throw light on the problem of their formation. The main plausible mechanisms for the formation of these satellites are discussd, including capture and breakup in the proto-Jovian nebula, collision within Jupiter's gravitational sphere of influence, and capture through the Jovian Lagrangian points after dissipation of the proto-Jovian nebula. UBV, VRI, and JHK color diagrams for various asteroids are used to show their similarity to the outer Jovian satellites. The evidence suggests that at least two outer Jovian satellites are comparable to C-type asteroids, and that two others are more nearly comparable to RD-type bodies. The apparent C-type satellites are both in the prograde cluster and the apparent RD-types are in the retrograde cluster. The Gradie and Veverka (1980) hypothesis that the reflectances and albedo characteristics of RD bodies may be due to aromatic kerogenlike compounds is discussed.

Cruikshank, D. P.↗
NASA NTRS1982

Synthesis and characteristics of poly/bisdichloromaleimides/

The characteristics of six bisdichloromaleimides with different aromatic structures are investigated. The compounds are prepared by reacting 2,3-dichloromaleic anhydride with 1,5-diaminonaphthaline; bis (m-aminophenyl)methylphosphine oxide; 2,5-bis (p-aminophenyl) 1,3,4-oxadiazole; 3,3-bis (p-aminophenyl)phthalide; 9,9-bis (p-aminophenyl) fluorene; 10,10-bis (p-aminophenyl)anthrone. Dynamic thermogravity is used to determine the effect of structural differences on the thermal characteristics of these compounds. These compounds are polymerized by nucleophilic displacement of chlorine with 9,9-bis (p-aminophenyl)fluorene. The polymers are then characterized by IR spectroscopy and reduced viscosity measurements. The anaerobic char yields of these polymers at 800 C are found to range from 55-60%. A complete loss of weight is observed between 600-650 C in the presence of air. In addition, the thermal cross-linking of these polymers is investigated.

Varma, I. K.↗