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  • 1
    Electronic Resource
    Electronic Resource
    Nematic polymers: Excluded-volume effects (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2315-2322 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a theoretical model which describes a cooperative helix-coil liquid-crystal phase transition. We show that this model predicts a first-order phase transition where certain types of chainlike macromolecules in solution make a transition from a nearly coiled to a nearly rigid conformation accompanied by a simultaneous development of long-range nematic-type liquid crystalline orientational order. From this model, the phase boundaries between nematic and isotropic phases are obtained as functions of concentration of macromolecules and of other physical parameters.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360180918
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and mechanical properties of injection-molded specimens of two-phase polymer blends (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 353-370 
    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: An experimental study was carried out to investigate the moldability of polymer blends which form two phases in the molten state and the effect of mixing on the morphology and mechanical porperties of molded specimens. Blends of polystyrene with polypropylene and blends of polystyrene with high-density polyethylene were used for this study. A plunger-type injection molding machine (Van Dorn) was employed for molding specimens. To improve the mixing performance of the plunger machine, a Static Mixer (Kenics Corp., Super Nozzle) was installed between the heating cylinder and the sprue. A number of different molding conditions (injection pressure, temperature, injection time, cooling time) were varied, and molded specimens were collected under each molding condition. The specimens were used for studying the degree of dispersion in the blends and for determining the mechanical properties. A differential thermal analysis (DTA) experiment was also carried out to determine the degree of dispersion of the blends in molded specimens. It was found that a linear correlation exists between the blend composition and thermal spectra area of the blends tested.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210205
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  • 3
    Electronic Resource
    Electronic Resource
    Poly-3-Hydroxyalkanoates containing unsaturated repeating units produced by pseudomonas oleovorans (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1367-1374 
    Details
    ISSN: 0887-624X
    Keywords: poly-β-hydroxyalkanoates ; bacterial polyesters ; Pseudomonas oleovorans ; functional polyesters ; reserve polyesters ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly-3-hydroxyalkanoates (PHAs) containing repeating units with terminal alkene substituents at the 3-position were produced by Pseudomonas oleovorans grown with either 7-octeneoic acid [OA(=)] alone, or 10-undeceneoic acid [UND(=)] alone, or mixtures of UND(=) and either nonanoic acid (NA) or octanoic acid (OA). For the latter, the biomass and PHA yields decreased as the fraction of UND(=) increased in the mixed carbon substrates. Essentially all of the repeating units in the PHA obtained from cells grown with UND(=) alone contained terminal alkene groups, including 3-hydroxy-10-undeceneoate, 3-hydroxy-8-noneneoate, and 3-hydroxy-6-hepteneoate units, but less than half of the units in the PHA from OA(=) had alkene substituents. The PHAs obtained from cells grown with various mixtures of UND(=) and either OA or NA were random copolymers, and the fraction of units with alkene substituents in these polymers increased in proportion to the fraction of UND(=) in the mixed carbon substrates. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330819
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  • 4
    Electronic Resource
    Electronic Resource
    Production of recombinant proteins in high-density insect cell cultures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 235-239 
    Details
    ISSN: 0006-3592
    Keywords: insect cells ; high density culture ; recombinant protein production ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of the growth phase of Spodoptera frugiperda (Sf9) cells on the production of recombinant proteins (β-galactosidase and glucocerebrosidase) was investigated. Cells infected with the recombinant Autographa californica nuclear polyhedrosis virus at the late exponential and stationary phases yielded low quantities of expressed protein. Highest enzyme yields were obtained using Sf9 cells from the early exponential phase (0.9 mg β-galactosidase/106 cells and 1.7 μg glucocerebrosidase/106 cells). Infection of resuspension of cells collected from various phases of growth in fresh medium resulted in 75% restoration of maximal expression levels. This finding suggested either nutrient limitation or waste product accumulation as the cause of the decrease in productivity at the latter phases of growth. Further experiments revealed that the highest productivity levels could be obtained with cultures of Sf9 cells grown in a fermentor to a cell concentration of 4 × 106 mL-1. The medium needed to be replaced prior to infection with the recombinant virus and supplemented with a mixture of glucose, L-glutamine, and yeastolate ultrafiltrate. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420211
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of air supplement on the performance of continuous ethanol fermentation system (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 12-16 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the purpose of improving ethanol productivity, the effect of air supplement on the performance of continuous ethanol fermentation system was studied. The effect of oxygen supplement on yeast concentration, cell yield, cell viability, extracellular ethanol concentration, ethanol yield, maintenance coefficient, specific rates of glucose assimilation, ethanol production, and ethanol productivity have been evaluated, using a high alcohol tolerant Saccharomyces cerevisiae STV89 strain and employing a continuous fermentor equipped with an accurate air metering system in the flow rate range 0-11 mL air/L/h. It was found that, when a small amount of oxygen up to about 80μ mol oxygen/L/h was supplied, the ethanol productivity was significantly enhanced as compared to the productivity of the culture without any air supplement. It was also found that the oxygen supplement improved cell viability considerably as well as the ethanol tolerance level of yeast. As the air supply rate was increased, from 0 to 11 mL air/L/h while maintaining a constant dilution rate at about 0.06 h-1, the cell concentration increased from 2.3 to 8.2 g/L and the ethanol productivity increased from 1.7 to 4.1 g ethanol/L/h, although the specific ethanol production rate decreased slightly from 0.75 to 0.5 g ethanol/g cell/h. The ethanol yield was slightly improved also with an increase in air supply rate, from about 0.37 to 0.45 ethanol/g glucose. The maintenance coefficient increased by only a small amount with the air supplement. This kind of air supplement technique may very well prove to be of practical importance to a development of a highly productive ethanol fermentation process system especially as a combined system with a high density cell culture technique.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260260104
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of dispersion structure of fermentation media by dynamic gas disengagement method (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 288-291 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370312
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  • 7
    Electronic Resource
    Electronic Resource
    Reaction mechanisms of polyacrylonitrile on thermal treatment (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1452-1457 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: A high-temperature radical scavenger, 2,2-diphenyl-l-picryl hydrazyl (DPPH), has been used to study the reaction mechanisms of polyacrylonitrile (PAN) on thermal treatment. The effect of DPPH on the cyclization reaction of PAN in both air and nitrogen, investigated by differential scanning calorimetry (DSC), helped to verify the proposed reaction mechanisms, i.e., the free radical and the ionic ones. For PAN homopolymer, the peak temperature of the reaction exotherm shifted to higher temperatures and the heat of reaction was decreased with increasing DPPH concentration. For PAN copolymer with methylacrylate and itaconic acid, however, the effects of DPPH on DSC thermograms were insignificant. The effects of IPPH suggest that the reaction of the nitrile groups proceeds by free radicals for the homopolymer while by ions for the copolymer. The activation energies for the thermal reactions of PAN in both air and nitrogen were also estimated by the dynamic DSC method, and they proved to be highly dependent on reaction mechanism, environment of thermal treatment, and DPPH concentration.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760332203
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature dependence of the nucleation effect of sorbitol derivatives on polypropylene crystallization (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1445-1451 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 temperature dependence of the nucleation effect of three sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) was studied by means of isothermal crystallization kinetic analysis. Isothermal crystallization thermograms obtained by differential scanning calorimetry (DSC) were analyzed based on the Avrami equation. The Avrami analysis for the nucleated iPP was carried out with DSC data collected to 35% relative crystallinity, and the rate constants were corrected assuming the heterogeneous nucleation and three dimensional growth of iPP spherulites. A semi-empirical equation for the radial growth rate of iPP spherulites was given as a function of temperature and was used to determine the number of effective nuclei at different temperatures. The number of effective nuclei in the nucleated samples was estimated to be 3 × 102 ∽ 105 times larger than that in the neat iPP. The logarithmic numbers of the effective nuclei decreased linearly with decreasing degree of supercooling in the range of crystallization temperatures tested. The temperature dependence of the effect of the nucleating agents on iPP crystallization was given quantitatively in terms of the deactivation factor defined as a fraction of the particles that are active at a particular temperature but inert at the temperature one degree higher. The nucleation activity and its temperature dependence are considered to be cooperative effects of many factors, including the dispersion and the physical or chemical nature of the agent as well as the interaction between the agent and the polymer. It is suggested that the temperature dependence of the effect of a nucleating agent should be treated as a characteristic of a given polymer/ nucleating agent mixture.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760332202
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  • 9
    Electronic Resource
    Electronic Resource
    Evolution of structure and properties in fiber formation from a thermoplastic polyester-polyether segmented copolymer (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 205-228 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Process-structure-property relationships in the formation of an elastic fiber from a melt of segmented polyester-polyether copolymers are described. The “soft” segment, polyethylene oxide, is modified to prevent its crystallization at use temperatures. Features of the polymer related to phase separation of the soft segments and the crystallizable “hard” segments are discussed. An “ideal” morphology of such a thermoplastic elastomeric fiber that would maximize its recoverable extension is defined, and a path toward its realization in a melt spinning process is described.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250116
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  • 10
    Electronic Resource
    Electronic Resource
    Melt rheological and thermodynamic properties of polyethylene homopolymers and poly(ethylene/α-olefin) copolymers with respect to molecular composition and structure (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 125-137 
    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: Various types of polyethylene homopolymers and copolymers, including linear high-density polyethylene (HDPE), branched low-density polyethylene (BLDPE), poly(ethylene vinyl acetate) copolymer (EVA), heterogeneous linear poly(ethylene/α-olefin) copolymer (het-LEAO) or commonly known as linear low-density polyethylene, homogeneous linear poly(ethylene/α-olefin) copolymer (hom-LEAO), and homogeneous branched poly(ethylene/α-olefin) copolymer (hom-BEAO), were evaluated for their melt rheological and thermodynamic properties with emphasis on their molecular structure. Short-chain branching (SCB) mainly controls the density, but it has little effect on the melt rheological properties. Long-chain branching (LCB) has little effect on the density and thermodynamic properties, but it has drastic effects on the melt rheological properties. LCB increases the pseudo-plasticity and the flow activation energy for both the polyethylene homopolymer and copolymer. Compared at a same melt index and a similar density, hom-LEAO has the highest viscosity in processing among all polymers due to its linear molecular structure and very narrow molecular weight distribution. Small amounts of LCB in hom-BEAO very effectively reduce the average viscosity and also improve the flow stability. Both hom-LEAO and hom-BEAO, unlike het-LEAO, have thermodynamic properties similar to BLDPE. © 1996 John Wiley & Sons, Inc.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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