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  • 1
    Digitale Medien
    Digitale Medien
    Velocity profiles of the exit region of molten polyethylene extrudates (1966)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966), S. 353-358 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The objective of the work described herein is the experimental investigation of the velocity field of polymer melts flowing through a capillary in the regons of flow prior to and after the capillary exit. The fluids studied are branched polyethylene melts in steady laminar isothermal flow. The technique employed for the determination of the Eulerian velocity profiles is one that utilizes phototomicrogroaphy of the reflected light from tracer particles dispersed in the flowing medium.Axial acceleration of the fluid elements just before the capillary exit was observed. It was found that this accelearation is more pronounced in melts of low bulk viscosity. This observation region, non-viscometric.The translation of the velocity profiles of the fluids studied, from one resembling a parabola to that of “plug” flow, involves inflection points with minima in the velocity vector v(r, z). These minima appear near the surface of the extrudates and can not be accounted for by an existing theory.It was also found that the density of the viscoelastic fluids studied is a function of the axial position, in the region of flow investigated. The density decreases before the exit and, before it reaches an equilibuiu value at an axial position downstream equal to one or two diameters, increases beyond that value upon exit. This phenomenon is attributed to an “overshoot” in the process fo elastic recoil of the high polymer melts fron a strained structure to a random one.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760060412
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  • 2
    Digitale Medien
    Digitale Medien
    Crystallization studies on deformed polybutene-1 melts (1971)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 11 (1971), S. 19-27 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: An apparatus was designed and built which allowed an investigation concerning the morphology and kinetics of crystallization of a deformed polybutene-1 melt. The polymer was quenched from a temperature above its melting point to one of two crystallization temperatures. The supercooled melt was then sheared and allowed to crystallize isothermally while the internal stress in the melt was continuously recorded. A polarizing microscope was employed for the simultaneous study of the resulting morphological changes. By properly accounting for thermal contractions within the apparatus caused by the quenching operation, as well as the imposed shear strain, a strain history of the polymer during crystallization was developed. From this strain history and the assumption that the volume contraction resulting from crystallization was isotropic, approximate kinetics of crystallization in a deformed polymer melt were determined.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760110105
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  • 3
    Digitale Medien
    Digitale Medien
    LDPE/PP blends modified by peroxide and radiation induced reactions (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 99-105 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: LDPE/PP polyblends, modified through either peroxide initiated reactions or irradiation, were characterized in terms of rheological and mechanical properties and microstructure. In the presence of peroxide, or through irradiation LDPE crosslinks, PP degrades. Data were obtained at two peroxide concentration levels (0.1 and 1% by weight) and two radiation doses (30 and 100 kGy). The results show that in peroxide modification, the degradation of PP prevails over the crosslinking of LDPE. However, the effect of irradiation of LDPE (crosslinking) is predominant over that of PP (degradation). The irradiation process tends to yield improved mechanical properties vs. peroxide modification for the PP-rich blends. In addition, the melt viscosity and elasticity of the irradiated PP-rich blends are higher than those of the peroxide-reacted blends at a given level of PP content and frequencies between 10 and 100 rad/s. Attempts were made to relate the shape of the rheological curves and the mechanical properties of the blends to the observed changes in their microstructure. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1994.070520112
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  • 4
    Digitale Medien
    Digitale Medien
    Thermomechanical studies of polymer deformation part I: A New deformation calorimeter (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 250-254 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The purpose of this paper is to describe a new deformation calorimeter, which is based on differential thermometry and uses a flowing gas stream as a heat transfer medium which allows it to operate under near-isothermal conditions. Also presented are some preliminary test measurements with a crosslinked polyurethane elastomer and crystalline polybutene-1.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760090404
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  • 5
    Digitale Medien
    Digitale Medien
    Structure-property modifications by fabrication operations (1964)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 4 (1964), S. 165-168 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Studies of polymer morphology under ideal conditions approaching equilibrium structures have been shown to be valuable in the development of an understanding of the relationship of properties to structure. Practical fabrication operations do not permit the achievement of equilibrium structures in commercial products and its is therefore necessary to study the effects of processing on the actual structures that result. In addition, an understanding of the effects of processing variables on properties permits the development of fabrication operations which can be directed toward the improvement of properties. Topics covered include the effects of hydrostatic pressure during processing, effects of combinations of pressure and thermal history, relationships between thermal history and crystallization rates in isotactic polymers and the kinetic and morphological effects of flow deformation on crystallizable plastics.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760040306
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  • 6
    Digitale Medien
    Digitale Medien
    The effect of molecular weight distribution on the melt flow behavior and the spectrum of relaxation times of polystyrene (1967)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 7 (1967), S. 318-323 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760070413
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  • 7
    Digitale Medien
    Digitale Medien
    Viscous dissipation in capillary flow of rigid PVC and PVC degradation (1968)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 8 (1968), S. 272-280 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The steady state, non-isothermal behavior of rigid polyvinyl chloride melt, flowing in capillaries of circular cross-section, was investigated by solving, with the aid of a digital computer, the momentum and energy balance equations. It was assumed that the polymer melt can be described by the “Power Law” constitutive equation. The shear rate, temperature and pressure dependent properties of the fluid were obtained experimentally. The effects of the thermal degradation of PVC on its viscosity, were also introduced in the equations of momentum and energy.The velocity, temperature and pressure profiles, obtained for both adiabatic flow and flow through a tube of constant wall temperature, indicate that considerable heating of the melt, due to viscous dissipation, can be achieved at moderate flow rates. Thermal degradation occurs in the capillary under certain conditions of temperature history and residence time of the fluid. The results of this work are in fair agreement with experimental results in this area.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760080407
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  • 8
    Digitale Medien
    Digitale Medien
    Structure-property studies in polymer melt rheology (1965)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 5 (1965), S. 130-134 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Various continuum theories of viscoelastic materials have predicted that extrudates issuing from a die will swell and this phenomenon is well known experimentally. One such continuum theory has been formulated by Pao in terms of relaxation times which can be evaluated independently in other tests. Since relaxation times are qualitatively understood in terms of molecular mechanisms, the swelling of extrudates can be given a molecular interpretation. We have found that the phenomenon originates from entanglement and those molecular motions characterized by relaxation times in the terminal zone of the viscoelastic spectrum. Extrudate swelling has been associated also with the capacity of materials to store energy. Since stored energy is also related to relaxation times, there must exist a functional relation between stored energy and swelling. For this same reason there must also exist a relation between swelling and recoverable strain. We have also presented in this paper some data concerning this latter relation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760050308
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  • 9
    Digitale Medien
    Digitale Medien
    Simulation of the mold-filling process (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 223-230 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The transport equations for a power law fluid are used to solve the transient and non-isothermal problem of filling a disk-shaped cavity. Using the results obtained it is possible to predict gate pressures, fill times and short shots. Furthermore, the velocity and temperature fields can be obtained throughout the filling process. This information specifies the formation of a frozen surface layer during filling. Rigid PVC was primarily used in the simulations, but some results are also given for linear polyethylene, nylon 6-6, ABS and polystyrene.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760140311
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  • 10
    Digitale Medien
    Digitale Medien
    Reactive polymer processing (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 838-846 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This paper addresses some of the general engineering problems in reactive polymer processing: thermal effects on reactor stability and polymer properties due to rapid exothermic polymerization, the formulation of reaction viscosity relationships required in simulations, and the generation of flow and mixing via technology available from both ends of the viscosity spectrum, which is spanned in its entirety when going from monomer to molded polymer. Methods of analysis are discussed and general design concepts are suggested, which can be applied to the construction of innovative future processing equipment.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760201303
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