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Wakelyn, N. T.

Publications and source records attributed to Wakelyn, N. T..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

X-ray diffraction studies of model compounds of thermoplastic polyimides

Several model compounds which represent aspects of the chemical structure of the Langley Research Center thermoplastic (LARC-TPI) have been synthesized for comparison studies using wide angle X-ray scattering (WAXS) as the discriminatory tool. The model compounds included N-phenylphthalimide, 3,3',4,4'-benzophenonetetracarboxylic diphthalimide, and N,N'-diphenyl-3,3',4,4'-benzophenonetetracarboxylic diphthalimide. X-ray diffraction studies of appropriate model compounds can yield information to aid in the understanding of polymeric crystallographic structure. Crystallinity and physical property changes can thus be induced into materials having complicated structures by chemical and thermal processes.

Wakelyn, N. T.↗
NASA NTRS1988

Graft copolymers from poly(2,6-dimethylphenylene oxide) and pivalolactone

The copolyether-polyester system resulting from the anionic graft polymerization of pivalolactone onto poly(2,6-dimethylphenylene oxide) has been formulated with differing graft densities and graft segment lengths. Wide angle X-ray scattering studies on these materials indicated an increased crystalline order with increased PVL segments/graft for similarly annealed specimens and a decrease in such order with increasing carboxylation.

Bell, Vernon L.↗
NASA NTRS1986

Solvent-Resistant, Thermally Stable Poly(Carbonate-Imides)

New polymers and copolymers based on polyimide backbone with carbonate moieties exhibit high temperature capability. Because of carbonate unit, many of these materials also exhibit high order or crystallinity. All of new imidecontaining polymers insensitive to acetone. New poly (carbonate-imide) exhibits significantly increased temperature resistance and shows less sensitivity to solvents than commercial polycarbonates.

St. Clair, T. L.↗
NASA NTRS1986

Estimation of crystallinity in a model thermoplastic composite

Crystallinities as low as 16 percent have been estimated by determination of the interplanar spacing on PET/carbonaceous filament composites with resin content of aobut 25 percent w/w using wide-angle X-ray scattering (WAXS) in the angular range 2 theta = 16-18 deg. The diffraction pattern of the carbonaceous reinforcements masks the major reflections of the resin, and the resin content and the crystallinity are kept low to make the simulation reasonable.

Wakelyn, N. T.↗
NASA NTRS1986

Resolution of wide-angle X-ray scattering from a thermoplastic composite

Wide-angle X-ray scattering from a polyetheretherketone/carbonaceous-fiber composite has been resolved using a curve-fit procedure. This resolution yielded under-curve areas for crystalline, amorphous, and fiber scatter which could be used as the basis for an estimation of crystallinity.

Wakelyn, N. T.↗
NASA NTRS1985

Characterization of a soluble polyimide

The solid phase thermal imidization of a soluble 4,4-prime-bis (3,4-dicarboxyphynoxy) diphenyl sulfide dianhydride plus 2,2-bis 4-(4-aminophenoxyl)phenyl hexafluoropropane (BDSDA-BDAF) polyimide precursor staged between 40 and 325 C was characterized by gel permeation chromatography, inherent viscosity, and number average molecular weight measurements. The information obtained indicated that this polyamic acid experienced an initial reduction in molecular weight during cure before achieving its ultimate molecular weight as a polyimide. The event was most likely related to the development of an anhydride band that appeared in the infrared spectrum around 1850/cm as the material cured. Correlation through infrared spectroscopy with a previous study dealing with several common, but insoluble, polyimide precursors, suggested that polyimides, in general, exhibit this trend in molecular weight behavior.

Young, Philip R.↗
NASA NTRS1985

Crystallinity determination by curvefit procedure for a semi-crystalline polymer

Wide angle X-ray scattering (WAXS) data from poly(etheretherketone) (PEEK) was resolved into a crystalline contribution represented as four reflections and an amorphous contribution represented as a broad, smoothly varying curve. The crystalline scatter is described as a linear combination of Cauchy and Gaussian functions while that of the amorphous halo is expressed as a cubic polynomial. Statistical analysis of the measured scattered intensity from an amorphous specimen with that calculated from the cubic polynomial, as a function of the combination parameter (fraction of Cauchy and Gaussian functions), suggests that the crystalline fraction of the polymer specimen studied is about 0.39.

Wakelyn, N. T.↗
NASA NTRS1985

Synthesis and properties of copoly(carbonate imides)

Copoly(carbonate imides) with varying amounts of carbonate in the backbone were prepared by reacting 4,4-prime-diaminodiphenyl carbonate and 4,4-prime diaminodiphenyl ether with benzophenonetetracarboxylic acid dianhydride in dimethylacetamide at room temeprature. Homopolymers of the two diamines as well as of 3,4-prime- and 3,3-prime-diaminodiphenyl carbonate were prepared in a similar procedure and their properties compared with those of the copolymers.

Maudgal, S.↗
NASA NTRS1984

On the structure of poly(etheretherketone) (PEEK)

Annealed, hot pressed, and melt-quenched PEEK specimens have been analyzed by wide-angle X-ray diffraction. The analysis suggests, in part, that structural studies based on the reported similarity between the structure of PEEK and that reported for poly(p-phenylene oxide) are valid and may be extended to a structure more in keeping with the chemical structure of the material.

Wakelyn, N. T.↗
NASA NTRS1984

Surface chloride salt formation on Space Shuttle exhaust alumina

Aluminum oxide samples from the exhaust of Space Shuttle launches STS-1, STS-4, STS-5, and STS-6 were collected from surfaces on or around the launch pad complex and chemically analyzed. The results indicate that the particulate solid-propellant rocket motor (SRM) alumina was heavily chlorided. Concentrations of water-soluble aluminum (III) ion were large, suggesting that the surface of the SRM alumina particles was rendered soluble by prior reactions with HCl and H2O in the SRM exhaust cloud. These results suggest that Space Shuttle exhaust alumina particles are good sites for nucleation and condensation of atmospheric water. Laboratory experiments conducted at 220 C suggest that partial surface chloriding of alumina may occur in hot Space Shuttle exhaust plumes.

Cofer, W. R., III↗
NASA NTRS1983

The application of forest classification from Landsat data as a basis for natural hydrocarbon emission estimation and photochemical oxidant model simulations in southeastern Virginia

The possible contribution by natural hydrocarbon emissions to the total ozone budget recorded in the Tidewater region of southeastern Virginia during the height of the summer period was examined. Natural sources investigated were limited to the primary HC emitters and most prevalent natural vegetation, the forests. Three types and their areal coverage were determined for Region VI of the Virginia State Air Pollution Control Board using remotely sensed data from Landsat, a NASA experimental earth resources satellite. Emission factors appropriate to the specific types (coniferous 0.24 x 10 to the 13th, mixed 0.63 x 10 to the 13th, deciduous 1.92 x 10 to the 13th, microgram/h), derived from contemporary procedures, were applied to produce an overall regional emission rate of 2.79 x 10 to the 13th microgram/h for natural non-methane hydrocarbons (NMHC). This rate was used with estimates of the anthropogenic NO(x) and NMHC loading, as input into a photochemical box model. Additional HC loading on the order of that estimated to be produced by the natural forest communities was required in order to reach certain measured summer peak ozone levels as the computer simulation was unable to account for the measured episodic levels on the basis of the anthropogenic inventory alone.

Salop, J.↗
NASA NTRS1980

Flashback-free combustor

All zirconia combustion chamber for testing fuels prevents "flashback" accidental extension of flame into fuel supply line. Chamber consists of hemispherical injector on base surrounded by hemispherical cap. Cap has two additional ports for thermocouple and gas sampling probes.

Anderson, S. G.↗
NASA NTRS1980

Comparison of measured ozone in southeastern Virginia with computer predictions from a photochemical model

Data for one day of the 1977 southeastern Virginia urban plume study are compared with computer predictions from a traveling air parcel model using a contemporary photochemical mechanism with a minimal description of nonmethane hydrocarbon (NMHC) constitution and chemistry. With measured initial NOx and O3 concentrations and a current separate estimate of urban source loading input to the model, and for a variation of initial NMHC over a reasonable range, an ozone increase over the day is predicted from the photochemical simulation which is consistent with the flight path averaged airborne data.

Wakelyn, N. T.↗
NASA NTRS1979

Computer predictions of photochemical oxidant levels for initial precursor concentrations characteristic of southeastern Virginia

A computer study was performed with a photochemical box model, using a contemporary chemical mechanism and procedure, and a range of initial input pollutant concentrations thought to encompass those characteristic of the Southeastern Virginia region before a photochemical oxidant episode. The model predictions are consistent with the expectation of high summer afternoon ozone levels when initial nonmethane hydrocarbon (NMHC) levels are in the range 0.30-0.40 ppmC and NOx levels are in the range 0.02-0.05 ppm. Calculations made with a Lagrangian model, for one of the previously calculated cases, which had produced intermediate afternoon ozone levels, suggest that urban source additions of NMHC and NOx exacerbate the photochemical oxidant condition.

Wakelyn, N. T.↗
NASA NTRS1978

Experimental and analytical study of nitric oxide formation during combustion of propane in a jet-stirred combustor

A jet-stirred combustor, constructed of castable zirconia and with an Inconel injector, was used to study nitric oxide formation in propane-air combustion with residence times in the range from 3.2 to 3.3 msec and equivalence ratios varying from 0.7 to 1.4. Measurements were made of combustor operating temperature and of nitric oxide concentration. Maximum nitric oxide concentrations of the order of 55 ppm were found in the range of equivalence ratio from 1.0 to 1.1. A finite-rate chemical kinetic mechanism for propane combustion and nitric oxide formation was assembled by coupling an existing propane oxidation mechanism with the Zeldovich reactions and reactions of molecular nitrogen with hydrocarbon fragments. Analytical studies using this mechanism in a computer simulation of the experimental conditions revealed that the hydrocarbon-fragment-nitrogen reactions play a significant role in nitric oxide formation during fuel-rich combustion.

Wakelyn, N. T.↗
NASA NTRS1976

Theoretical study of reactive and nonreactive turbulent coaxial jets

The hydrodynamic properties and the reaction kinetics of axisymmetric coaxial turbulent jets having steady mean quantities are investigated. From the analysis, limited to free turbulent boundary layer mixing of such jets, it is found that the two-equation model of turbulence is adequate for most nonreactive flows. For the reactive flows, where an allowance must be made for second order correlations of concentration fluctuations in the finite rate chemistry for initially inhomogeneous mixture, an equation similar to the concentration fluctuation equation of a related model is suggested. For diffusion limited reactions, the eddy breakup model based on concentration fluctuations is found satisfactory and simple to use. The theoretical results obtained from these various models are compared with some of the available experimental data.

Gupta, R. N.↗