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  • Chemistry  (19)
  • 1970-1974  (19)
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  • 1
    Electronic Resource
    Electronic Resource
    Radical formation during the tensile failure of polymer fibers (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 171 (1973), S. 211-227 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Bruch von linearen Makromolekülen als Folge der Dehnungsdeformation von orientiertem Nylon 6 wurde mit Elektronenspinresonanz (ESR) an zwei Proben, einer Einzelfaser (Borste) und technischem, weing verdrilltem Garn, untersucht. Die Ergebnisse an der Einzelfaser zeigen, daß die Dehnungsdeformation in einer wesentlichen, irreversiblen Weise die Konzentration der freien Radikale, doch nicht die Bruchspannung und Deformation beeinflußt. Das mechanische Verhalten des Garns in Bruchnähe ist völlig verschieden von dem der Einzelfaser. Die vorliegenden Versuche lassen ernste Zweifel aufkommen an der Korrektheit frühererBerichte, in denen angenommen wurde, daß die mittels ESR beobachteten Kettenbrüche eindeutig den Deformations- und Bruchprozeß bestimmen.
    Notes: Bond rupture associated with the tensile deformation of oriented Nylon 6 has been studied by electron spin resonance (ESR). Two samples were investigated, a single monofilament (“bristle”) and a commercial low twist yarn. Experiments with the monofilament show that tensile deformation has substantial irreversible effects on the free radical concentration observed at failure, but no effect on the ultimate properties of the fiber. It was also demonstrated that the stress-strain behavior of the yarn is quite different from that of the fibers near the ultimate extension. These present experiments raise serious questions as to the correctness of previous reports in which the bond breakage observed by ESR is assumed to uniquely determine the deformation and fracture process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021710120
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  • 2
    Electronic Resource
    Electronic Resource
    Flow of water through highly swollen membranes (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 865-870 
    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 difference between the hydraulic permeability K under a pressure gradient and the diffusive permeability P under a concentration gradient can be explained by the incipient viscous flow at high degree of swelling. This flow is opposed by the friction resistance of the macromolecules of the highly swollen membrane. It comes to an end at a critical swelling Hc when the number of permeant molecules is not more sufficient for a complete solvation of the macromolecules of the membrane. Below this swelling, K equals PV1/RT, where V1 is the molar volume of the permeant, and above it the difference K - PV1/RT is proportional to H/(1 - H) - Hc/(1 - Hc). The proportionality factor depends on the friction coefficient of the macromolecular segments and on the average lateral chain clustering. The data on poly(glycerol methacrylate) suggest that on the average the aggregates contain two chains.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1972.070160406
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  • 3
    Electronic Resource
    Electronic Resource
    IR-Studies of drawn polyethylene part III. The orientation of vinyl and methyl end-groups (1971)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 150 (1971), S. 163-177 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das anfängliche Anwachsen und die baldige Sättigung des Dichroismus verschiedener Banden von Methyl- und Vinylendgruppen im kaltverstreckten Polyäthylen wurden im Zusammenhang mit der mittleren Orientierung der Endgruppen und der angrenzenden CH2-Gruppen (freie Kettenenden) untersucht. Mehrere mögliche Konformationen der Endgruppen in Bezug zur Hauptkette wurden diskutiert. Im Falle der Methylendgruppen kann man die Experimentalergebnisse auf zwei Arten deuten: (a) Wenn die Orientierung ausschließlich von den Methylendgruppen im Kristallgitter herrührt, dann können sich nur 17 bis 35% dieser Gruppen im Kristallverbande befinden. (b) Sind alle Endgruppen in der amorphen Phase, dann erhält man für die Orientierungsfunktion der Endgruppen und der freien Kettenenden f = 0,4-0,8. Der Dichroismus der Vinylendgruppenbanden kann nicht so eindeutig erklärt werden. Der auf Grund der stabilsten Konformation zu erwartende Dichroismus der Vinylendgruppen ist im qualitativen Widerspruch mit den Versuchsergbnissen. Die mit dem beobachteten Dichroismus in Einklang stehende Konformation, die zu einer Orientierungsfunktion f = 0,55 für die Vinylendgruppen und die freien Kettenenden führen würde, ist kein stabiles Rotationsisomeres, wie man es auf Grund des Rotationspotentials einfacher Modellverbindungen erwarten würde. Die Gründe für diese Diskrepanz werden diskutiert.
    Notes: The first increasing and soon saturating IR dichroism of several bands originating from methyl and vinyl end-groups in cold drawn linear polyethylene has been related to the mean orientation of the end-groups and the preceding CH2 sequences (cilia). Several possible conformations of the end-groups with respect to the backbone chain are discussed. In the case of the methyl end-groups the experimental data can be interpreted in two ways: (a) Assuming that the orientation results exclusively from methyl end-groups which are incorporated in the crystal lattice, it follows that only 17-35% of these groups can be in the crystalline phase. (b) If all end-groups are located in the amorphous phase one can derive an orientation function for the end-groups and the cilia given as f = 0.4-0.8. The dichroism of bands resulting from the vinyl end-groups cannot be interpreted unequivocally. The expected dichroism of a vinyl end-group in its supposed most stable conformation is in qualitative disagreement with the experimental value. The conformation which is consistent with the observed dichroism and would lead to an orientation function f = 0.55 for the vinyl end-groups and the cilia, does not represent a stable rotational isomer as discussed from the rotational potential of simple model compounds. Reasons for this discrepancy are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1971.021500113
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  • 4
    Electronic Resource
    Electronic Resource
    Plastic deformation and structure of extruded polymer solids (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 627-632 
    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: During extrusion the main deformation and orientation of macromolecules is achieved by the flow component with longitudinal gradient. The orientation increases drastically if some solidification occurs during flow, yielding row-nucleated cylindrites and even fully oriented hard elastomers. In all cases the basic elements are stacks of very thin (∼100Å) folded-chain lamellae connected by very few tie molecules. The plastic deformation of the solid transforms the original lamellar material into the extremely well oriented fibrous structure with high anisotropy of physical properties. The basic element are the highly aligned, very long and thin microfibrils bundled into fibrils. The axial strength of microfibrils is caused by the great many taut tie molecules connecting as almost crystalline bridges the crystalline blocks across the interposed amorphous layers. In plastic deformation of fibrous material the fibrils are sheared and longitudinally displaced. The latter mode is responsible for almost all the observed elongation. It smooths the structural defects on the surface of fibrils caused by the ends of microfibrils and thus produces a better lateral fit of fibrils resulting in rapidly increasing resistance to plastic deformation. The former mode extends the interfibrillar tie molecules and hence drastically increases their fraction per amorphous layer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760140907
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  • 5
    Electronic Resource
    Electronic Resource
    Gas permeability of deformed polyethylene films (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 531-546 
    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: Low-density polyethylene films strained up to 35% exhibit an initial increase of diffusivity and permeability which soon reach a maximum and subsequently drop to steadily decreasing values below those of the unstrained starting material. The sorption steadily increases and seems to approach a plateau. The maximum and the subsequent decrease are probably caused by significant, recoverable plastic deformation which seems to depress the tortuosity factor but not the free volume, as one concludes from the opposite trend of diffusion and sorption. Permanently deformed drawn or rolled films on the strain range from 0.5 through 3.0 exhibit a continuous decrease of diffusivity and permeability with an almost constant reduction of sorption. This postulates a decrease in free volume and a steadily decreasing tortuosity factor as a consequence of the gradually increasing fraction of the new, practically impermeable fibrous structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1974.070180218
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of compacting pressure on the permeability of vectorized membranes for liquids (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1493-1505 
    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 theory of liquid diffusive flow through graded membrane under applied pressure difference is developed and demonstrated on four simple models. The grading of the membrane, caused by a gradient of chemical composition or physical structure, results in a gradient of liquid uptake (hydration) which in turn is reduced by the compacting pressure existing in the membrane during the permeation experiment. The hydration established in equilibrium between the swelling tendency and compacting pressure determines the local permeability. It has different values K+ = K- for opposite flow direction. The total membrane permeability 〈K〉, however, depends on the current direction only in the case that the relative depression of local hydration, and hence of permeability by pressure, is not uniform but has a gradient. In mathematical formulation, the directionality of membrane requires the local permeability to be an irreducible function of location and pressure p, continuously increasing or decreasing with x. Th permeability of the membrane is higher if the driving pressure is applied at the side of the membrane with higher relative reduction of hydration and permeability by compacting pressure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1971.070150616
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  • 7
    Electronic Resource
    Electronic Resource
    Vapor and gas permeability of asymmetric membranes (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 3127-3136 
    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 membrane with continuously varying and pressure-dependent local permeability P may show a dependence of transport property for gases and vapors on the direction of flow. Such an asymmetry occurs only if the deviation of local permeability from ideality varies from layer to layer. In mathematical formulation, this means that the local permeability is an irreducible function of location and pressure, i.e., not a product of a function of location and a function of pressure. The membrane permeability is higher if the side with greater deviation from ideal, i.e., constant permeability, is exposed to the higher pressure. For two simple cases the currents in both directions and their ratio at constant pressure difference were calculated. It turns out that the asymmetry of permeability increases with increasing deviation from ideality up to a maximum, after which the membrane tends to return to symmetry. An additional result of this investigation is the conclusion that Fick's law, i.e., the proportionality of the diffusion current to the negative concentration gradient is inapplicable not only to inhomogeneous membranes but also to homogeneous not ideal membranes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1971.070151220
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  • 8
    Electronic Resource
    Electronic Resource
    Diffusive and bulk flow transport in polymers (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 433-442 
    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 transport properties of polymer membranes in various forms which have a wide variety of practical applications, such as ultrafiltration, dialysis and blood oxygenation, depend upon the structure (homogeneous or heterogeneous) and the transport characteristics of the membrane material. Among many possible driving forces of transport, the pressure gradient and the concentration gradient are considered to be the most general forces encountered in practical use of polymer membranes. The transport of various permeants (gas, dissolved gas, liquid solvent, and solute) through porous and homogeneous (nonporous) polymer membranes under these driving forces is discussed. In the absence of a pressure gradient, the transport of permeants can be described as diffusion, regardless of the permeant phase and the membrane structure. In the presence of a pressure gradient, the transport of permeants may occur by diffusion and/or bulk flow of the permeants, depending upon the membrane structure and the nature of the permeant. In homogeneous membranes, many noninteracting permeants such as gases and nonsolvent vapors permeate by diffusion under applied pressure gradient: however, solvent in homogeneously swollen membranes moves by bulk flow and the diffusion depending on the degree of swelling of the membrane. In heterogeneous membranes under applied pressure, most permeants move by bulk flow.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070170209
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  • 9
    Electronic Resource
    Electronic Resource
    Plastic deformation of nylon 6 single crystals and thin membranes (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 157 (1972), S. 131-139 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die bei der Deformation von Einkristall-Lamellen auftretenden Risse zeigen zwei bevorzugte, unter 60° zueinander stehende Richtungen. Die Risse sind eng bei Kristallen, die unmittelbar auf der Mylar-Unterlage liegen, und wesentlich breiter in den oberen Schichten von Lamellenpaketen. Die primäre Richtung der Risse läuft parallel zu der Ebene der Wasserstoffbrückenbindungen. Die Mikrofibrillen, die die Risse überbrücken, sind zu kurz, um brauchbare Dunkelfeldaufnahmen erhalten zu können. Deformierte dünne Filme zeigen gelegentlich eine Lamellar-Struktur. Nach dem Tempern bei 215°C werden gut orientierte Einkristallblöcke, die zu den Mikrofibrillen gehören, beobachtet.
    Notes: The deformation of single crystals shows two preferential directions for crack formation at 60° to each other. The cracks open very little on crystals lying directly on the Mylar substrate and substantially more on the higher layers of a multilayer crystal. The primary crack direction is parallel to the plane of hydrogen bridges. The microfibrils bridging the cracks are too short for a good dark field electron micrograph. Deformed thin membranes occasionally show a lamellar structure. After annealing at 215°C well oriented single crystal blocks belonging to microfibrils can be observed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021570112
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  • 10
    Electronic Resource
    Electronic Resource
    The influence of irradiation and hydration on the transport properties of isotropic and anisotropic membranes (1971)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 147 (1971), S. 175-184 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß der Quaternisierung auf Transporteigenschaften von Wasser und Natriumchlorid unter umgekehrten Osmose-Bedingungen wurde für alternierende Copolymere von Styrol und 4-Vinylpyridin untersucht.Diese Ergebnisse zeigen sehr deutlich eine lineare Abhängigkeit zwischen log P als Funktion der Salzretention oder der reziproken Hydratation. Solch eine Beziehung scheint für alle ionischen Polymeren zu gelten. Darüber hinaus zeigen die Ergebnisse, die bei der Bestrahlung der Polymeren erhalten wurden, daß die Zugdehnungseigenschaften dieser Copolymeren ungefähr um 60% verbessert werden konnten bei einer optimalen Dosis von ungefähr 9 megarad. Zusätzlich konnte eine gerichtete Permeabilität von Membranen, in die ein Quaternisierungsgradient eingefügt worden war, bei einem alternierenden Copolymeren gezeigt werden. Der Wasser- und der Salzfluß waren bei der Membran in Richtung des Quaternisierungsgradienten höher als in der umgekehrten Richtung.
    Notes: The influence of quaternization on the transport properties of water and sodium chloride under reverse osmosis conditions has been examined for alternating copolymers of styrene and 4-vinyl pyridine. These results demonstrate quite clearly a linear relationship between log P as a function of salt rejection or reciprocal hydration. Such a relationship seems to be quite general for ionic polymers. Also, results with irradiation demonstrate that tensile properties of these copolymers can be improved by about 60% at an optimum dose of about 9 megarads. In addition, the directional permeability of graded membranes has been demonstrated for an alternating copolymer where a gradient of quaternization was imposed on the membrane. Both the water and salt flux were higher along the quaternization gradient than in the reverse orientation of the membrane.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1971.021470115
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