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  • 1
    Electronic Resource
    Electronic Resource
    The relation between melt flow properties and molecular weight of polyethylene (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 277-292 
    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 non-Newtonian behavior of commercial linear polyethylene samples and their fractions were studied at 190°C. The viscosity η versus shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} curves of whole polymers could be superimposed onto a single master curve despite the variations of their molecular weights and molecular weight distributions. For fractions, however, the same master curve was inapplicable, and the sensitivity of the viscosity to shear rate was found to be greater than those of the whole polymers. The zero-shear viscosities η0 of fractions were related to the 3.42 power of the weight-average molecular weight Mu as follows: \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _0 = 2.39 \times 10^{ - 15} M_{w^{3.42} } . $\end{document} For whole polymers, the zero-shear viscosities were found to be considerably higher at the same Mw and markedly lower at the same z-average molecular weight Mz than those of the fractions. Thus, it was concluded that η0 corresponds to an average of molecular weight between Mw and Mz. It was found that the molecular relaxation time τ is proportional to Mz5.3 for whole polymers and to η0Mw for fractions. Using these relations it was possible to relate the flow ratio, the ratio of flow rates at two different shear stresses, with the molecular weight distribution.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1971.070150203
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of flow behavior of polyethylenes and polypropylenes with graessley's theory (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 1465-1475 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Graessley's theory of non-Newtonian behavior of linear polymers is tested with data on polyethylenes and polypropylenes having a wide range of molecular weights and molecular weight distributions, and for a polyethylene fraction. Theoretical flow curves derived by using molecular weight distribution data from column fractionations are in good agreement with experimental curves obtained from a cone-and-plate viscometer and an extrusion-type rheometer, when the distribution is assumed to cut off at a maximum molecular weight. The experimentally obtained relaxation time for entanglement is found to be proportional to the Rouse relaxation time, though the former is about one decade smaller than the latter.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180110801
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  • 3
    Electronic Resource
    Electronic Resource
    Mixing efficiency for polymer blends of very different molecular weights by using a mixing nozzle (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 557-565 
    Details
    ISSN: 1042-7147
    Keywords: polymer blend ; polyethylene ; nozzle ; mixing device ; ESC ; 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
    Notes: A way to mix polymer blends of very high and low molecular weights by using a mixing nozzle is presented. An array of blend nozzles with a conical inlet attached to a single screw extruder was used to blend polyethylene homopolymers with very different molecular weights. Using extruders with 30 and 50 mm barrel diameters, the effects of nozzle dimensions and operation conditions with respect to the homogeneity were studied.The device proved useful in obtaining a good macroscopic and molecular homogeneity up to 30 kg/hr by the 50 mm extruder, though care must be taken to avoid the degradation of polymers by heat and shear, especially in the extruder.The key factor ruling the efficiency of blending was found to be the compression ratio, i.e. the ratio of the cross sectional areas of the entrance of the nozzle and that of the orifice, and the shear rate at the orifice.For the nozzle with geometrically similar figure, the critical shear rate at which the homogeneity began to worsen was the same. Scale-up of the nozzle could be accomplished by enlarging the diameter of the diameter of the orifice, yet maintaining a geometrically similar figure. The maximum output of the nozzle is proportional to the third power of the orifice diameter.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1995.220060802
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  • 4
    Electronic Resource
    Electronic Resource
    Mixing device for polymer blends of very different molecular weights using a mixing nozzle process (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 549-556 
    Details
    ISSN: 1042-7147
    Keywords: polymer blend ; polyethylene ; nozzle ; mixing device ; ESC ; 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
    Notes: A new method of blending two polymers with very different molecular weights, i.e. different melt viscosities, in which the polymer mixture is forced to pass through a nozzle with a conical taper is proposed in this study.High density polyethylenes with very high and very low molecular weights were used as the samples in the blending process, and the parameters that affected the homogeneity of the blended polymers were studied. The homogeneity was found to be better at a lower shear rate, smaller orifice diameter, higher compression ratio of the cross-sectional area of the nozzle entrance and orifice, and a small length-to-diameter ratio of the orifice. This blending process, the nozzle blend, was found to make the droplets of a high molecular weight component extend to thin fibers along the conical section of the nozzle.The nozzle blend system has been proved to be useful in obtaining both macroscopic and microscopic homogeneity, and has been estimated to be comparable to a few minutes of roll-mill blending.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1995.220060801
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  • 5
    Electronic Resource
    Electronic Resource
    The environmental stress cracking of linear ethylene copolymers (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 593-601 
    Details
    ISSN: 1042-7147
    Keywords: ESC ; polyethylene ; apparatus ; ethylbranch ; SEM ; 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
    Notes: A new method of measuring the environmental stress cracking (ESC) of polymers at constant strain is proposed in which an occurrence of fracture is detected automatically. The new method showed a very good reproducibility within 10% compared with a few hundred percent by conventional methods.The ESC values obtained by the new method was found to be proportional to those by the conventional Bell Telephone Laboratory method in which the ESC was determined by the occurrence of small cracks, with a proportionality contant of 2.8. From the fact that the difference of both ESCs were also proportional to the ESC determined by the BTL method, it was concluded that the value of the ESC was proportional to the velocity of crack propagation. These conclusions were supported by the observation of the test pieces by a scanning electron microscope.The study of the blended polymers revealed that the additivity of logarithmical ESC with weight fraction holds for a wide range of polymes, which enables estimation of ESCs up to millions of hours.Using this technique, the ESCs of a wide range of molecular weights and a number of short chain branches were studied. It was found that the branches in the high molecular weight polymer were much more effective on the ESC than those in the low molecular weight polymer. This makes it possible to design a good resin with a good ESC.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1995.220060901
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  • 6
    Electronic Resource
    Electronic Resource
    Chromatographic fractionation of polystyrene: An evaluation of the nature of column fractionation (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1303-1314 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Column chromatographic fractionation of polystyrene was carried out with the methyl-ethyl ketone-methanol system, and effects of various experimental conditions on the fractionation efficiency were studied. For samples with molecular weights below about 6 × 105, neither the temperature gradient (0.7°C/cm), nor the flow rate of solvent (30-270 ml/hr) seriously influences the fractionation efficiency. The effect of temperature gradient becomes apparent only in the high molecular weight region and only if the gradient of the solvent composition is too steep. High flow rates (ca. 125 ml/hr) clearly affect the fractionation efficiency for a high molecular weight sample (Mw = 5.46 × 105). Precipitation chromatography for the fractionation system was calculated from the phase equilibrium data according to the mass transport equation proposed by Schulz et al. The theoretical analysis gives support to the observed dependence of the temperature effect on molecular weight. Comparison of the observed and theoretical relations between elution volume and molecular weight of the fraction, on the other hand, indicates that the process of fractionation is simply elution of polymer off the support without reprecipitation. Certain conditions of polymer deposition on the support are required for optimal results.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.160070802
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