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  • Articles: DFG German National Licenses  (30)
  • Chemistry  (30)
  • Chemical Engineering  (4)
  • 11
    Electronic Resource
    Electronic Resource
    Drag reduction by polymer-polymer mixtures (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 837-858 
    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 extensive study on the turbulent drag reduction caused by the various mixtures of polyacrylamide, purified guargum, xanthangum, and their graft copolymers has been conducted at low concentrations and Re = 14,000 using a turbulent flow rheometer. It has been found in most of the cases that the drag reduction caused by mixtures shows a positive deviation from the linearly additive straight line. This effect is more prominent when the drag reduction caused by both the constituents differ appreciably. In most of the cases, the drag reduction caused by the mixtures is higher than the DR caused by either of the constituent polymers; however, the drag reduction caused by the mixture is less than the sum of the drag reduction caused by both the constituents at their respective concentration in the mixture. It has also been noticed that there is no evidence of synergism in these mixtures at low concentrations.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360409
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  • 12
    Electronic Resource
    Electronic Resource
    Turbulent drag effectiveness and shear stability of xanthan-gum-based graft copolymers (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 2933-2948 
    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: A number of graft copolymers of xanthan gum and polyacrylamide have been synthesized by grafting acrylamide onto xanthan gum using the ceric-ion-initiated solution polymerization technique. The effects of various synthesis parameters such as amount of catalyst, reaction time, and ratio of xanthan and acrylamide on drag reduction effectiveness of the graft copolymers have been studied. The scaling up of grafting reaction has been accomplished in 40-L reactor. The drag reduction effectiveness of the graft copolymers is investigated over a wide range of concentrations and Reynolds numbers. It is shown that the maximum drag reduction obtainable in xanthan gum solutions above 300 ppm can be obtained in solutions of graft copolymers at concentrations of 100-150 ppm. The grafting also improves the shear stability at higher Reynolds numbers. The shear stability of the graft copolymers at constant wall stress has been found to be superior to polyacrylamide and the mixtures of polyacrylamide and xanthan gum. In general, the shear stability of graft copolymers and polyacrylamide is shown to increase with concentration. The drag reduction characteristics and shear stability have been discussed in terms of structural features of the graft copolymers. The drag reduction characteristics of the graft copolymers are found to be similar to those of flexible polymers.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070371012
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  • 13
    Electronic Resource
    Electronic Resource
    Investigation on multiphase polymeric systems of poly(vinyl chloride). I. PVC-chlororubber-20-gp-styrene-acrylonitrile (2 : 1) blends (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 2491-2515 
    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: A graft copolymer [chlororubber-20-gp-styrene-acrylonitrile (2 : 1)] has been synthesized by a solution precipitation polymerization technique grafting styrene and acrylonitrile onto chlororubber-20 main chain. The graft copolymer has been characterised by elemental analysis, IR spectroscopy, and viscometry. It has been blended with PVC by melt mixing using a Brabender plasticorder and extrusiograph. The mechanical properties such as flexural and tensile strengths and impact strength of the blends have been studied to evaluate its performance as an impact modifier. The behavior of PVC-chlororubber-20-gp-styrene-acrylonitrile (2 : 1) blends has also been compared with PVC-chlororubber-20 and PVC-KM-365B (a commercial acrylate modifier) blends. The thermal behavior of these blends has also been studied. It has been found that PVC-chlororubber-20-gp-styrene-acrylonitrile (2 : 1) blends have higher impact strength than PVC-chlororubber-20-gp blends though the PVC-KM-365B blends have the highest impact strength. Based on the authors' previous compatibility studies along with present X-ray diffraction studies and the morphological investigation of the fractured surface by scanning electron microscopy, the mechanical behavior of these blends have been explained in the framework of existing theories. A model has been proposed to account for the optimum dispersion and adhesion of graft polyblends of chlororubber-20 in PVC matrix.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370904
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  • 14
    Electronic Resource
    Electronic Resource
    Photoinitiated oxidation of heterophasic ethylene-propylene copolymers. I. Comparison of oxidation productsN.C.L. Communication No. 5681. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1871-1881 
    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: Detailed photoproducts from photoirradiation of heterophasic ethylene-propylene copolymers and their fractions have been compared by infrared spectroscopy combined with chemical derivatization. The oxidized films were treated with gaseous NH3, SF4, and NO for the rapid identification and resolution of the various carbonyl species, alcohols, and hydroperoxides. The photoproduct formation depends upon the composition of the sample. The heterogeneities in thin films were also determined by micro FTIR spectroscopy. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070501103
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  • 15
    Electronic Resource
    Electronic Resource
    Polybutadiene content and microstructure in high impact polystyrene (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 953-959 
    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 polybutadiene (PB) content and its microstructure in different grades of high impact polystyrene (HIPS) has been studied by various spectroscopic techniques. PB is characterized by deformation bands in FTIR spectroscopy at 994, 967, 912, and 729 cm-1. FT-Raman was used for higher constant resolution over the range of wave numbers. It provides reasonable signal to noise ratios in near IR excited Raman. Proton and 13C-NMR spectroscopy was utilized for the determination of polybutadiene content in HIPS and tacticity, and reactivity ratios. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Thermal stability of PVC/chlororubber-20-graft polyblend-styrene-acrylonitrile blends. I (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1297-1308 
    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: Thermal stability of PVC blends with chlororubber-20-graft polyblend-styrene-acrylonitrile [CR-20gp-SAN (2:1)] was studied by HCI evolution techniques and thermogravimetry under isothermal condition. The thermal stability of PVC/CR-20gp-SAN (2:1) blends has been compared with those of PVC/CR-20 and PVC/KM-365B blends. It has been observed that the thermal stability of modified PVC is less than that of unmodified PVC. The CR-20gp-SAN (2:1) modified PVC blends were found to be more stable than PVC/CR-20 blends but less stable than PVC/KM-365B blends. The rate of degradation in PVC blends were observed to be unaffected by the concentration of the modifiers, but the PVC/KM-365B blends were found to be degrading slower in comparison with PVC/CR-20 and PVC/CR-20gp-SAN (2:1) blends. The rate of degradation for PVC/CR-20 blends at lower concentrations (〈10%) of modifiers is almost equal to that of PVC/CR-20-gp-SAN (2:1) blends, but more at higher concentrations of modifiers (〉10%). The experimental results have been explained on the basis of the chemical nature of the modifiers and their miscibility with PVC.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290423
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  • 17
    Electronic Resource
    Electronic Resource
    Cell death in bioreactors: A role for apoptosis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 720-726 
    Details
    ISSN: 0006-3592
    Keywords: cell death ; apoptosis ; hybridoma cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The incidence of apoptotic and necrotic cell death was compared in CHO, SF9 insect cells and murine plasmacytoma (J558L) and hybridoma (TB/C3) cells during in vitro cultivation in batch cultures. Acridine orange staining and fluorescence microscopy enabled the visualization of a classic morphological feature of apoptotic cell, the presence of condensed and/or fragmented chromatin. DNA gel electrophoresis was employed to show an additional characteristic of the process, the endonuclease-mediated fragmentation of DNA into multiples of 180 base pairs. The levels of apoptosis at the end of batch cultures of plasmacytoma and hybridoma cell lines were found to be 60% and 90% of total dead cells, respectively. However, employing the above-mentioned techniques, the biochemical and morphological features of apoptosis were not found in CHO and SF9 insect cells. Some factors affecting the induction of apoptosis during the batch culture of the hybridoma and plasmacytoma cell lines were identified. The most effective inducer was found to be glutamine limitation, followed by (in order of importance) serum limitation, glucose limitation, and ammonia toxicity. Blockage of the cell cycle of the plasmacytoma and hybridoma cells using thymidine resulted in the induction of apoptosis. This has important implications for the development of cell culture processes that minimize cell division and thereby increase specific productivity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440608
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  • 18
    Electronic Resource
    Electronic Resource
    Cell cycle and cell size dependence of susceptibility to hydrodynamic forces (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 88-92 
    Details
    ISSN: 0006-3592
    Keywords: cell cycle ; hydrodynamic forces ; apoptosis ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exposure of animal cells to intense hydrodynamic forces exerted in turbulent capillary flow, and by controiled agitation and aeration, resulted in preferential destruction of S and G2 cells and the extent of destruction of these cells was dependent upon the intensity of the action. The loss of these cells was possibly due to their larger size. However, the appearance of large numbers of membrane-bound vesicular structures similar to apoptotic bodies as well as cells with low DNA stainability (in a sub-G1 peak) suggested that the action of adverse hydrodynamic forces on these large cells may at least in part be to induce an apoptotic response. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460112
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  • 19
    Electronic Resource
    Electronic Resource
    Death mechanisms of animal cells in conditions of intensive agitation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 463-472 
    Details
    ISSN: 0006-3592
    Keywords: apoptosis ; animal cell death ; hybridoma cells ; agitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The question is addressed as to whether cells which are subject to high-energy dissipation rates in agitated bioreactors show an apoptotic response. Murine hybridoma cells in batch culture were agitated in bench-scale (1-L) bioreactors without gas sparging. At an energy dissipation rate of 1.5 W m-3 there was no apparent damage. At 320 W m-3 cell viability declined, and increasing proportions of the dead cells displayed the morphological features of apoptosis, but necrosis also remained as a significant mechanism of death. When cells were subjected to the intensive energy dissipation rate of 1870 W m-3 in a bioreactor without gas headspace, the cell number dropped by 50% within 2 h and a subpopulation of smaller-sized cells emerged. This excluded trypan blue but showed some apoptotic characteristics such as reduced and condensed DNA content and low F-actin content. The incidence of apoptotic activity was further demonstrated by the appearance of numerous apoptotic bodies. Analysis of the cell cycles of both small and normal size populations indicated that greater proportions of S and G2 cells had become apoptotic and there was evidence of preferential survival of G1 cells. It is suggested that two mechanisms of cell death are apparent in hydrodynamically stressful situations, but their relative expression depends on the energy dissipation rate. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450602
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  • 20
    Electronic Resource
    Electronic Resource
    Turbulent drag reduction by polymer-fiber mixtures (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 2467-2478 
    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 turbulent drag reduction studies by asbestos fiber mixtures with purified guargum, purified xanthangum, and their graft copolymers have been conducted at low concentration and Re 14000 using turbulent flow rheometer designed by Hoyt. A method for making stock suspension of asbestos fibers is also suggested which gives better drag reduction. It has been found from the present studies that purified guargum-asbestos fiber mixtures give positive synergistic effect even at low concentration and synergism in drag reduction may be caused by a mixture when its constituents are rigid. A simple mixture rule equation having interaction parameter may be used for the prediction of drag reduction by the mixture.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330716
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