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  • Wiley-Blackwell  (2)
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1388-1396 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bubble instabilities observed in film blowing using four different polyolefins are discussed: high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP). Special attention is given to the effect of the frost line height on the bubble stability, an effect mostly ignored in the literature. A video-camera system was used to record the bubble shape and oscillations. In general, three forms of instabilities and combinations were observed: (1) axisymmetric periodic variations in the bubble diameter; (2) helical motions of the bubble; and (3) variations in the position of the solidification line. The four resins show different stability behaviors. The LDPE has the most stable operating space and the PP is the most unstable one. No correlation was observed between bubble stability and oscillatory shear rheological properties of the resins. Instability is enhanced by increasing take-up ratio, increasing blow-up ratio, and decreasing frost line height. Furthermore, for the LDPE, some operating points were not attainable and multiple steady states were observed. Our results are in a poor agreement with the predictions Cain and Denn's 1988 analysis.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-6266
    Keywords: interfacial tension ; breaking thread ; polyamide ; polyethylene ; interface ; modifier morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Compared to the dynamic mixing process used in melt blending operations, most techniques for measuring the interfacial tension can be considered as virtually static. For this reason, in order to measure the interfacial tension of an A-B immiscible system in the presence of an interfacial modifier, the problem of migrating the modifier to the interface is a central issue. In this study, the influence of the addition of an interfacial modifier, a polyethylene copolymer ionomer, on the interfacial tension between two high-density polyethylenes and a polyamide is investigated. The breaking thread method is used and the interfacial tension is measured as a function of ionomer content. In order to enhance the likelihood of placing the modifier in closer proximity to the interface, various sample preparations are compared. In all cases, the interfacial tension significantly drops with increasing ionomer content and tends to a limiting value. It is shown, however, that the preparation of the system for the breaking thread experiment via coextrusion using a conical die brings the modifier in closest proximity to the interface. With this approach an additional 1.45 times reduction of the interfacial tension at 10% compatibilizer concentration (based on the mass of HDPE) is observed compared to the classical technique of preparation. Confirmation of this effect is demonstrated using X-ray photoelectron spectroscopy where analysis of the thread surface of the system prepared by coextrusion indicates a more than fourfold enrichment of interfacial modifier. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1947-1958, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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