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  • 1985-1989  (2)
  • 1960-1964  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    CONTACT ANGLE RELATIONSHIPS ON SILICA AQUAGEL SURFACES (1962)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 66 (1962), S. 1790-1798 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100816a005
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  • 2
    Electronic Resource
    Electronic Resource
    MODIFICATION OF GROWTH RATE AND HABIT OF ADIPIC ACID CRYSTALS WITH SURFACTANTS (1961)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 65 (1961), S. 1730-1737 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100827a014
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  • 3
    Electronic Resource
    Electronic Resource
    POLYCATION-POLYANION COMPLEXES: PREPARATION AND PROPERTIES OF POLY-(VINYLBENZYLTRIMETHYLAMMONIUM) POLY-(STYRENESULFONATE) (1961)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 65 (1961), S. 1765-1773 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100827a020
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  • 4
    Electronic Resource
    Electronic Resource
    Ethanol production by nitrogen-deficient yeast cells immobilized in a hollow-fiber membrane bioreactor (1985)
    Springer
    Applied microbiology and biotechnology 23 (1985), S. 85-91 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Cells ofSaccharomyces cerevisiae ATCC 4126, immobilized within the macroporous walls of asymmetric hollow-fiber membranes, were alternately perfused with 10% glucose complex medium and with 10% glucose defined medium which was deficient in nitrogen. Using complex growth medium, ethanol productivities during the initial 10 h of culture attained a maximum level of 133 g/l-h based on the total fiber volume (3% ethanol). Productivities during nitrogen deficiency stabilized at 10 g/l-h (0.5 ethanol). In subsequent growth phases, ethanol production rates increased to levels 40–70% of initial growth-phase values, but the ability to regenerate the fermentation activity decreased with culture age. During nitrogen deficiency, the fermentation efficiency declined with a concomitant reduction in the total protein concentration of immobilized cells within the hollow-fiber membranes. The molar ratio of acetaldehyde to ethanol increased seven-fold during nitrogen deficiency, indicating that the overall decline in glycolytic activity was accompanied by preferential reduction in alcohol dehydrogenase activity. The molar ratio of glycerol to ethanol increased two-fold during nitrogen deficiency, and large lipid-like droplets accumulated within the nitrogen-deficient cells. In addition to these findings, we conclude that current hollow-fiber membrane reactors should be limited to cell cultures having low growth rates, low O2 requirements, and low CO2 production rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01982722
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  • 5
    Electronic Resource
    Electronic Resource
    Ethanol production by nitrogen-deficient yeast cells immobilized in a hollow-fiber membrane bioreactor (1985)
    Springer
    Applied microbiology and biotechnology 23 (1985), S. 85-91 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Cells ofSaccharomyces cerevisiae ATCC 4126, immobilized within the macroporous walls of asymmetric hollow-fiber membranes, were alternately perfused with 10% glucose complex medium and with 10% glucose defined medium which was deficient in nitrogen. Using complex growth medium, ethanol productivities during the initial 10 h of culture attained a maximum level of 133 g/l-h based on the total fiber volume (3% ethanol). Productivities during nitrogen deficiency stabilized at 10 g/l-h (0.5 ethanol). In subsequent growth phases, ethanol production rates increased to levels 40–70% of initial growth-phase values, but the ability to regenerate the fermentation activity decreased with culture age. During nitrogen deficiency, the fermentation efficiency declined with a concomitant reduction in the total protein concentration of immobilized cells within the hollow-fiber membranes. The molar ratio of acetaldehyde to ethanol increased seven-fold during nitrogen deficiency, indicating that the overall decline in glycolytic activity was accompanied by preferential reduction in alcohol dehydrogenase activity. The molar ratio of glycerol to ethanol increased two-fold during nitrogen deficiency, and large lipid-like droplets accumulated within the nitrogen-deficient cells. In addition to these findings, we conclude that current hollow-fiber membrane reactors should be limited to cell cultures having low growth rates, low O2 requirements, and low CO2 production rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938958
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  • 6
    Electronic Resource
    Electronic Resource
    Transport of liquids in structurally modified polyethylene (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 897-933 
    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: Cast linear polyethylene films subjected to dry and solvent annealing display markedly different sorption and difusion barrier properties than do untreated films. The subsequent sorption of liquid o- and p-xylene and cis- and trans-acetylene dichloride per unit volume of amorphous polymer increases as the annealing temperature and/or treating solvent concentration increases. Integral diffusivities calculated from sorption and steady-state permeation rates show a monotonic increase with sorption per unit volume of amorphous polymer. The concentration dependence, however, is less marked than observed in similar systems at low permeant activity. Apparently the above treatment reduces the effective crosslinking imposed by the crystallites on the amorphous polymer chains through disentangling and incorporating some of these chains into crystallites. Thus the polymer is capable of a greater degree of swelling when brought into contact with a compatible liquid in a spite of a higher degree of crystallinity. The low concentration dependence of the diffusivities is probably due to heterogeneous distribution of excess permeant in a treated film. If the excess permeant were preferentially sorbed in regions of low polymer concentration then the above observations could be explained. Long-duration, osmotic stress-induced swelling and recrystallization have been cited to account for time-dependent permeation rates in treated and untreated films.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080229
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  • 7
    Electronic Resource
    Electronic Resource
    Flow of gases through polyethylene (1961)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 50 (1961), S. 413-439 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion and permeability constants for twelve permanent gases have been measured in a linear and a branched polyethylene, hydrogenated polybutadiene, and natural rubber over the temperature range 5-55°C. The Barrer time lag apparatus has been used in these determinations. For all gas-polymer pairs investigated, a linear plot of the logarithm of the diffusion or permeability constants versus the reciprocal absolute temperature is observed, indicating activated diffusion is occurring. Arguments have been presented supporting the hypothesis that natural rubber is a completely amorphous analog of polyethylene with respect to the diffusion process. It has been possible, as a result, to quantitatively express the reduction in diffusion constants in going from natural rubber to hydrogenated polybutadiene (29% crystalline), to the branched polyethylene (43% crystalline), and to the linear polyethylene (77% crystalline). These reductions were strongly dependent on gas molecular size, increasing as the molecular size increases. A geometric impedance factor and a chain immobilization factor have been introduced to account for the effect of crystallinity. The former is assumed to be independent of molecular size and accounts for the necessity of the diffusing molecule to by-pass crystallites which have been shown to be impenetrable. The latter size-dependent factor reflects the reduction in amorphous chain segment mobility brought about through the proximity of crystallites. Analysis of the geometric impedance factor supports the existence of thin, highly anisometric sheets of crystalline polymer in polyethylene. The anisometry of the crystallites was observed to increase with increasing crystallinity consistent with the chain folding mechanism for crystal growth in polyethylene. Nucleation and growth kinetics also qualitatively accounted for the variation in crystal anisometry observed in polymers prepared by different methods of polymerization. The apparent activation energies for diffusion determined in polyethylene include not only the energy required for chain segment separation but also the effect of thermal expansion and crystalline melting. Correlations have been presented which permit the estimation of gas diffusion constants in a wide variety of polyethylenes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1961.1205015412
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  • 8
    Electronic Resource
    Electronic Resource
    Solubility of gases in polyethylene (1961)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 50 (1961), S. 393-412 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solubility constants for thirteen permanent gases were measured within the temperature range 5-55°C. in a linear and a branched polyethylene, hydrogenated polybutadiene, and natural rubber. Equilibrium and time lag solubility determinations were made, the latter being indirectly obtained as the ratio of the permeability to the diffusion constants. Within experimental precision, equilibrium and time lag measurements were in agreement. The solubility of each gas in polyethylene was found to be proportional to the volume fraction of amorphous material when the polymer was treated as a simple, two-phase mixture of crystalline and amorphous polymer, each with a characteristic specific volume. Even the small helium molecule exhibited no detectible solubility in the crystallites according to this model. Therefore, a solubility constant in completely amorphous polyethylene could be determined for each gas which, with the density of an arbitrary sample, would enable calculation of the solubility of each gas in that particular sample. A correlation of the solubility constants in completely amorphous polyethylene was obtained from a thermodynamic model of the disolution process. Comparison of this correlation with a similar one for normal hydrocarbon liquids emphasized the analogy between the amorphous phase in polyethylene and these low molecular weight substances. The solubility constants in natural rubber, a completely amorphous polymer under the experimental conditions, were approximately 50% higher than those in amorphous polyethylene. Higher intermolecular forces due to the unsaturation in natural rubber may account for this result. The apparent heats of solution of all gases in branched polyethylene were approximately 1.0 kcal./g. mole more positive than those in linear polyethylene. This behavior was shown quantitatively, by comparison with dilatometric data, to be simply the result of crystalline melt-out in branched polyethylene. In linear polyethylene the experimental solubility data yielded essentially true heats of solution, since negligible crystalline melt-out occurred between 5 and 55°C. These were correlated quite satisfactorily by further application of the thermodynamic model for the dissolution process. Available evidence, therefore, indicates that the crystallites in polyethylene are impenetrable, and are randomly distributed on a macroscopic scale with respect to the diffusion and dissolution processes. The amorphous phase behaves as a homogeneous liquid whose thermodynamic properties are independent of the mode of polymer preparation, thermal history of the sample, and level of crystallinity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1961.1205015411
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetics of precipitation polymerization of vinyl chloride (1962)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 60 (1962), S. 121-140 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of vinyl chloride in solution in tetrahydrofuran, and in cyclohexane, with AIBN initiator, has been studied over the monomer concentration range 3-14 mole/1. at 40 and 50°C., via a dilatometric technique. In tetrahydrofuran (a relatively good solvent for the polymer), polymerization rate is second order in monomer, and 0.7 order in initiator; DP is very low (∼100) at monomer concentrations below 10 mole/1. and relatively insensitive to monomer or initiator concentration. Below 10 mole/1. the reaction is either homogeneous, or the polymer separates as a solvated gel without evidence of autoacceleration. Above 10 mole/1., however, the polymer separates as a granular solid, autoacceleration is observed, and DP increases several fold. In cyclohexane (a poor solvent), polymer precipitates from the outset of the reaction, and autoacceleration is observed at all monomer concentrations. Polymerization rate is first order in monomer, half order in initiator, first order in polymer at low polymer concentration, and two-thirds order in polymer at high polymer concentrations. DP is high, and essentially linear in monomer concentration. Results in tetrahydrofuran are interpreted as indicating that the solvent functions as a retarder, forming (by transfer from monomer) relatively unreactive radicals. In cyclohexane (as in bulk monomer), normal homogeneous kinetics govern the reaction in solution, but precipitated polymer particles function as secondary loci for propagation. A simplified moving-boundary treatment of diffusion of radical activity into and out of a thin surface layer of a growing polymer particles satisfactorily accounts for the observed rate dependency on polymer concentration. Kinetic differences between the precipitation polymerization of vinyl chloride and acrylonitrile are believed attributable to the extremely high frequency of radical transfer to monomer in the former system.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1962.1206017006
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  • 10
    Electronic Resource
    Electronic Resource
    Gas transmission in irradiated polyethylenePresented at the XVIIIth International Congress of Pure and Applied Chemistry, Montreal, Canada, August 1961. (1963)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 1 (1963), S. 895-919 
    Details
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The transmission of helium, nitrogen, methane and propane was studied in samples of a high pressure, branched polyethylene (46% crystalline) irradiated to a dose in air of 108 roentgens from a Co60 source. By using a time-lag apparatus the permeability, diffusion, and solubility constants were measured in the temperature range 0-55°C. These data were compared with those obtained in samples of the above polymer beforeirradiation. Infrared analysis indicates that oxidation, unsaturation, and croaslinking had resulted from irradiation of the polymer. Because of a possible gradient in chemical composition through the irradiated films, the usual analysis of the time-lag data may not have been applicable to the present work. The apparent diffusion and solubility constants were, however, qualitatively consistent with the anticipated effects of the chemical and physical changes resulting from irradiation. The apparent solubility constants were uniformly higher by 40% in the irradiated film as compared to the values in the unirradiated films. No reduction in crystallinity was observed upon irradiation, so this increase was ascribed to the effect of chemical composition changes. A thermo-dynamically consistent increase in the apparent heats of solution was also observed. The apparent diffusion constants were lower in the irradiated samples with the fractional reduction increasing with gas molecular diameter. The reduction for helium was 30%, while that for propane was 54%. The apparent energies of activation for diffusion showed no significant change upon irradiation. Arguments are presented to indicate that the reduced apparent diffusion constants apparently arose from the mild cross-linking which had occurred in the amorphous phase. Comparisons are made between the gas transmission data obtained in the unirradiated samples with those for other high pressure, branched polyethylenes studied in this laboratory in light of a simple model for gas flow in the crystalline-amorphous matrix.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1963.100010306
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