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  • FLUID MECHANICS AND HEAT TRANSFER  (11)
  • Polymer and Materials Science  (6)
  • AEROSPACE MEDICINE  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Miniemulsion polymerization of styrene: Evolution of the particle size distribution (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1381-1389 
    Details
    ISSN: 0887-624X
    Keywords: particle size distribution ; evolution of latex particles ; miniemulsion polymerization; evolution of particle size ; mechanism of miniemulsion polymerization ; particle nucleation in miniemulsion polymerization ; calorimetry, miniemulsion polymerization of styrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of the miniemulsion polymerization of styrene was investiaged through a combination of calorimetry to monitor the polymerization rate and transmission electron microscopy (TEM) to follow the evolution of the particle size distribution. These techniques proved to be a powerful combination for gaining detailed mechanistic information regarding these polymerizations. Particle size analysis of the latexes withdrawn during the course of the reaction revealed that most of the polymer particles were formed by a relatively low conversion (i.e., 10% conversion). However, nucleation continued well past this point (to 40-60% conversion). In fact, it was observed that nucleation in miniemulsion polymerizations using cetyl alcohol continued past the maximum in the rate of polymerization. As a result of these long nucleation periods, the latex particle size distributions produced from these miniemulsion polymerizations were broader than their conventional emulsion polymerization counterparts, and were negatively skewed with a tail of small particles. The amount of negative skewing of the particle size distributions was found to decrease with increasing initiator (potassium persulfate) concentration. Finally, a correlation was observed between the length of time to the maximum polymerization rate and the breadth of the particle size distribution as reflected in the standard deviation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330822
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of the presence of polymer in miniemulsion droplets on the kinetics of polymerization (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2365-2376 
    Details
    ISSN: 0887-624X
    Keywords: miniemulsion polymerization, kinetics ; styrene/polystyrene, miniemulsion polymerization ; reactor calorimeter, miniemulsion polymerization ; latex particles via nucleation in droplets ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution of polystyrene in styrene were dispersed in an aqueous gel phase comprising sodium lauryl sulfate, cetyl alcohol, and water using an emulsification process known to produce monomer droplet sizes inthe submicron size range (referred to as miniemulsion droplets). The shelf-life stabilities of these miniemulsions were studied to determine their relative droplet sizes, and the emulsions were concommitantly polymerized in an isothermal batch reaction calorimeter. The polymerization kinetics and final particle sizes produced were compared with miniemulsion and conventional emulsion polymerizations prepared using equivalent recipes without the addition of polystyrene. The results indicate that polymerization of miniemulsions prepared from polymer solutions produce significantly different kinetics than both miniemulsion and conventional emulsion polymerizations. In general, a small amount of polymer greatly increases the rate of polymerization and the final number of particles produced in the polymerization to the extent where even conventional polymerizations carried out above the critical micelle concentration of the surfactant polymerize more slowly. The results are explained by considering the system to be comprised of small, stable pre-formed monomer-swollen polymer particles which are able to efficiently capture aqueous phase radicals. This enables the system to produce a large final number of particles, similar to the initial number of pre-formed polymer particles, as opposed to miniemulsions and micelles in which only a relatively small fraction of the initial number of species (droplets or micelles) become polymer particles. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321217
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  • 3
    Electronic Resource
    Electronic Resource
    Tack in urethane elastomers (1965)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 9 (1965), S. 523-533 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The phenomenon of tack has been studied in urethane-urea elastomers prepared from polyether or polyester prepolymers and 4,4′-methylenebis(2-chloroaniline). It is shown that tack at zero elongation is attained only in polymers in which the flexible chains, i.e., polyesters or polyethers, contain 50 chain links or more. This coincides with the requirements for the Gaussian vector function in elastomers. The results suggest that, in the absence of flexible chain ends in these polymers, tack is solely contributed by the flexible segments along the polymer chains, while the rigid blocks in the chains do not participate in the formation of tack.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1965.070090214
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of photolyzed elastomersProd. No. 1453 (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 245-249 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The extent of photolysis of the surface of an elastomer may be characterized semiquantitatively by utilizing the physical model of a two-ply stressed beam. A brief mathematical exposition is given. This permits a numerical estimate of the degree of chain scission and crosslinking occurring in the surface during photolysis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110207
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of average molecular weight of cellulose acetate by dielectric dispersion in solutionThis research was carried out under contracts with the Office of Ordnance Research, U.S.A., No. 36-034-ORD-1240 and No. 36-034-ORD-1943. (1957)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 24 (1957), S. 19-26 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The capacity of cells containing solutions of 5% cellulose acetate in dioxane was measured from 50 cycles to as high as 5 megacycles by a bridge method. A dispersion region was found between zero and approximately 40 kc. The frequency where the dielectric dispersion was 0.50 was taken as the critical frequency which was found to be related to the viscosity determined degree of polymerization. An empirical correlation enabled the calculation of degrees of polymerization from dielectric dispersion which could be readily duplicated and which agreed reasonably well with those found by the viscosity method. It is suggested that this procedure may develop into a very convenient and rapid method for molecular weights pending the accumulation of further experimental evidence.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1957.1202410503
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  • 6
    Electronic Resource
    Electronic Resource
    A new technique for studying photooxidative erosion of polymer films (1957)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 24 (1957), S. 311-314 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1957.1202410618
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  • 7
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    Experimental and predicted heating distributions for biconics at incidence in air at Mach 10 (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Heating distributions were measured on a 1.9-percent-scale model of a generic aeroassisted vehicle proposed for missions to a number of planets and for use as a moderate lift-drag ratio Earth orbital transfer vehicle. This vehicle is spherically blunted, 12.84 deg/7 deg biconic with the fore-cone bent upward 7 deg to provide self-trim capability. A straight biconic with the same nose radius and the same half-angles was also tested. The free-stream Reynolds numbers based on model length were equal to about 2 x 10(5) or 9 x 10 (5). The angle of attack, referenced to the aft-cone, was varied from 0 deg to 20 deg. Heating distributions predicted with a parabolized Navier-Stokes (PNS) code are compared with the measurements for the present Reynolds numbers and range of angles of attack. Leeward heating was greatly affected by Reynolds number, with the heating increasing with decreasing Reynolds number for attached flow (low incidence). The opposite was true for separated flow, which occurred when the fore-cone angle of attack exceeded 0.8 times the fore-cone half-angle. Windward heating distributions were predicted to within 10 percent with the PNS code. Leeward heating distributions were predicted qualitatively for both Reynolds numbers, but quantitative agreement was poorer than on the windward side.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-2334 , L-15785 , NAS 1.60:2334
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Laminar heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity flows (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Laminar heating distributions were measured at hypersonic-hypervelocity flow conditions on a 1.9-percent-scale model of an aeroassisted vehiclee proposed for missions to a number of planets. This vehicle is a spherically blunted, 12.84/7deg biconic with the fore-cone axis bent upward 7 deg relative to the aft-cone axis to provide selftrim capability. Also tested was a straight biconic (i.e., without nose bend) with the same nose radius and half-angles as the bent-nose biconic. These measurements were made in the Langley Expansion Tube at free-stream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6.0 to 9.0 with helium, nitrogen, air, and carbon dioxide test gases. The range of calculated thermochemical equilibrium normal-shock density ratios for these four test gases was 4 to 19. Angles of attack, referenced to the aft-cone, varied from 0 to 20 deg. Heating distributions predicted with a parabolized Navier-Stokes (PNS) code were compared with measurement for helium and air test gases. Measured windward and leeward heating levels were generally underpredicted by the PNS code for both test gases, and agreement was poorer on the leeward side than on the windward side.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-2213 , L-15645 , NAS 1.60:2213
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Transcutaneous measurement of volume blood flow (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-155233
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Program and charts for determining shock tube, and expansion tunnel flow quantities for real air (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program in FORTRAN 4 language was written to determine shock tube, expansion tube, and expansion tunnel flow quantities for real-air test gas. This program permits, as input data, a number of possible combinations of flow quantities generally measured during a test. The versatility of the program is enhanced by the inclusion of such effects as a standing or totally reflected shock at the secondary diaphragm, thermochemical-equilibrium flow expansion and frozen flow expansion for the expansion tube and expansion tunnel, attenuation of the flow in traversing the acceleration section of the expansion tube, real air as the acceleration gas, and the effect of wall boundary layer on the acceleration section air flow. Charts which provide a rapid estimation of expansion tube performance prior to a test are included.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TN-D-7752 , L-9700
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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