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  • Polymer and Materials Science  (83)
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  • 1
    Electronic Resource
    Electronic Resource
    Twist, writhe, and geometry of a DNA loop containing equally spaced coplanar bends (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 235-250 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of a topologically closed DNA loop is important in many biological processes, including the regulation of transcription, recombination, and replication. Modeling DNA as an isotropic elastic rod, we use finite element analysis to show that the dependence of the twist (ΔTw) and the writhe (Wr) upon the linking number deficit (ΔLk) is strongly influenced by intrinsic bends. We determine how the geometry of a DNA loop changes as a function of the number of uniformly spaced coplanar 20° bends, oriented so as to open toward the center of the loop. We also calculate the geometry of DNA rods that are smoothly bent to the same extent. The response of both ΔTw and Wr of a bent DNA to changes in ΔLk falls into one of three categories, depending upon the number of bends. For a single bend of 20°, Wr increases monotonically with ΔLk and the change in ΔTw with distance is constant along the entire DNA axis. For two to ten 20° bends, Wr passes first through a local maximum, then through a local minimum, and finally increases monotonically as ΔLk increases. For eleven to eighteen 20° bends, Wr again varies monotonically with ΔLk. For all numbers of bends greater than two, the ΔTw per unit length depends upon the distribution of intrinsic bends, being constant between any two adjoining bends but varying with their position relative to the cut location. Accompanying these ΔLk-associated changes in Wr and ΔTw per unit length are characteristic changes in geometry that are specific for each category. The results of these calculations raise the possibility that intrinsic bends can serve as a control factor in the biological functions associated with loop formation in DNA. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Plastics rheology. R. S. LENK, Wiley (Interscience), 1968. 214 pp. $11.00 (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 483-484 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080315
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  • 3
    Electronic Resource
    Electronic Resource
    A continuum theory of nonlinear viscoelastic deformation with application to polymer processing (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 1129-1146 
    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 continuum theory of nonlinear viscoelastic behavior has been developed which is applicable to the quantitative description of the rheological properties of high polymeric materials. Particular classes of deformations have been investigated. Special emphasis has been placed upon nonlinear effects in viscoelastic fluids such as normal stresses and variable viscosity. Two new classes of flows are defined: sufficiently smooth flow and isoelastic flow.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080309
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  • 4
    Electronic Resource
    Electronic Resource
    Milling behavior of gum elastomers: Experiment and theoryContribution No. 253 from the Research Center of the United States Rubber Company, Wayne, New Jersey. (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1011-1026 
    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: When an uncompounded elastomer is processed on a two-roll mill, four different regions of mechanical behavior are observed, depending upon the temperature and the severity of the nip deformation. this behavior is observed on materials with a wide variety in chemical composition, through the severity varies. The flow at high temperatures is typical of melt or polymer solution behavior. At lower temperatures unstable flow and elastic solidike regions are observed. By presuming the elastomer to be an isotropicviscoelastic medium, the stress and velocity fields were computed in the polymer melt region. The unstable regime was found to correspond to a critical value of the ratio of viscoelastic to viscous forces. The mathematical analysis, done interms of the Green-Rivlin-Noll theory of viscoelastic media, extends earlier studies of deformation in this geometry by Gaskell and Bergen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070100705
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  • 5
    Electronic Resource
    Electronic Resource
    Elastomer processing and application of rheological fundamentalsProd. No. 1452 (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 321-334 
    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: Elastomer processing operations are discussed and classified as unit operations. The theory of nonlinear viscoelasticity is applied to processing unvulcanized amorphous rubber and the significance of the maximum relaxation time τm is emphasized.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110301
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  • 6
    Electronic Resource
    Electronic Resource
    Melt spinning of nylon 6: Structure development and mechanical properties of as-spun filaments (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 2341-2358 
    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 structure of melt-spun nylon 6 filaments was studied using on-line x-ray diffraction and birefringence measurements. Measurements were also made on as-spun and treated filaments. On-line wide-angle x-ray scattering measurements indicated that crystallization did not occur on the nylon 6 spinline at spinning rates up to 1000 m/min when spinning was done into either ambient air of 60% relative humidity or into wet saturated air. The filaments did crystalline gradually on the bobbin to a paracrystalline pseudohexagonal (γ) form. The rate of crystallization was dependent on the molecular orientation developed in the spun filaments. Crystalline orientation factors based on hexagonal symmetry were computed as a function of take-up velocity for fibers which were conditioned 24 hr in air at 65% relative humidity. Annealing in air or treatment in water or 20% formic acid solution causes a transformation from the pseudohexagonal form to the α monoclinic form. The tangent modulus of elasticity and tensile strength of spun and conditioned filaments increase with increasing take-up velocity and spinline stress, while elongation to break decreases with these variables.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210905
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of titanium dioxide on the rheological and extrusion properties of polymer melts (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 501-523 
    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 of the influence of titanium dioxide (TiO2) on the rheological and extrusion properties of five polymer melts (two low-density polyethylenes, two high-density polyethylenes, and a polystyrene) has been carried out. Increasing TiO2 loading increases the shear viscosity η, with the extent of increase being greater at lower shear rates. At moderate and high TiO2 loadings, the filled melts may possess yield values. Empirical equations relating viscosity to filler loading have been developed. The first normal stress difference was measured for the melts and found to increase with increasing TiO2 loading. However, the extent of increase was less than found for the viscosity function and interpretation in terms of the theory of viscoelasticity suggests that the characteristic relaxation time of the melts decreases with increasing TiO2 level. Empirical equations relating the first normal stress difference coefficient to volume fraction of the filler have been developed. Addition of TiO2 is found to decrease extrudate swell and retard the occurrence of extrudate distortion.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1976.070200222
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  • 8
    Electronic Resource
    Electronic Resource
    Basic study of extrusion of polyethylene and polystyrene foams (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1013-1026 
    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 fundamental study of bubble morphology development and apparent rheological properties in foam extrusion is reported. The influence of melt temperature, die length/diameter ratio, and blowing agent level on the morphology are considered. Measurements of the influence of blowing agent on viscosity, extrudate swell, and end-pressure losses are described. The viscosity is reduced, but extrudate swell is increased. End-pressure losses were found to become very large relative to the die wall shear stress at low extrusion rates. These results were interpreted in terms of bubble development. The filling of molds by foaming melts was observed and is described.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230406
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  • 9
    Electronic Resource
    Electronic Resource
    Solution and rheological properties of poly(m-phenyleneisophthalamide) in dimethylacetamide/LiCl (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 2155-2168 
    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 of the solution properties of poly(m-phenyleneisophthalamide) (MPD-I) in dimethylacetamide (DMA)/LiCl solutions is presented. Differential refractometry, light scattering photometry, dilute and concentrated solution viscometry, and normal stress experiments are reported and interpreted. This polymer in the concentration range investigated does not exhibit mesophase behavior in contrast to its para-linked analog. Generally, it behaves as a flexible polymer molecule; however, its capacity to become a polyelectrolyte strongly influences its behavior in the presence of LiCl. MPD-I is self-associated when dissolved in pure DMA but dissociates in DMA/LiCl solvent systems. The Zimm plots of MPD-I in DMA/LiCl solutions show distortion, probably due to polymer-salt interactions.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230726
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  • 10
    Electronic Resource
    Electronic Resource
    Shear flow rheological properties, fiber damage, and mastication characteristics of aramid-, glass-, and cellulose-fiber-reinforced polystyrene melts (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 1217-1244 
    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 of the viscosity and principal normal stress difference of a polystyrene melt filled with aramid (Kevlar), glass, and cellulose fibers is reported. The influence of loading level and mastication on the rheological properties is discussed. The effects of mixing and mastication on fiber damage are considered. Glass fibers break down rapidly to very small aspect ratios, while aramid shows a “kinked” structure, with kinks occurring every 100 μm. A mechanism is proposed for fiber breakage based on buckling during rotation in shear flow. It is found that addition of fibers increases the viscosity in the same manner as a reduction in temperature, and data may be superposed by reduced plotting. This indicates that the viscosity increase is due solely to enhanced viscous dissipation in the matrix and not to interparticle forces as is the case with smaller particles. The principal normal stress difference increases at fixed shear stress with fiber loading. The extent of increase depends upon fiber loading, aspect ratio, and modulus.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1980.070250623
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