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  • 1
    Electronic Resource
    Electronic Resource
    Mechanical behavior of injection-molded starch-based polymers (1996)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 784-790 
    Details
    ISSN: 1042-7147
    Keywords: starch-based polymers ; biomaterials ; injection molding ; Scorim ; impact performance ; 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: This work evaluates the mechanical performance of injection-molded starch-based copolymers, 60/40 (mol/mol) starch/poly(ethylene vinyl alcohol), and the possibility of improving material properties through deliberately induced anisotropy during processing. Different types of samples were produced by conventional and shear-controlled injection molding (Scorim) and tested under tensile and impact loading. The behavior of three distinct grades is discussed in terms of the respective fracture morphology (evaluated by scanning electron microscopy). A comparison is made between the behavior of conventional and Scorim samples. The results show that the mechanical properties of the materials used were significantly improved by the employment of the Scorim process. The stiffness values of the conventional moldings were doubled, without reducing the ductility of the polymer. The impact data showed a material sensitivity, and consequent loss of properties, to the localized shear imposed to the melt during processing. This situation is attributed to very narrow mold gates (in the case of pingated systems) and leads to much reduced impact performance.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of shear controlled orientation in injection moulding on the mechanical properties of an aliphatic polyketone (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 415-430 
    Details
    ISSN: 0887-6266
    Keywords: aliphatic polyketone ; ethylene-carbon monoxide copolymer ; PK ; isotactic polypropylene ; injection moulding ; molecular alignment ; morphology ; SCORIM ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article relates to an investigation of injection moulding a new commercial polymer, an aliphatic polyketone (PK). A terpolymer and a 30% glass-filled grade were used as study materials together with an isotactic polypropylene that was used as a basis for comparison. Both conventional injection moulding and shear-controlled orientation injection moulding (SCORIM) were employed in processing. Tensile testing was carried out at 80°C as well as at room temperature. Polarized light microscopy and wide-angle x-ray diffraction were used in the characterization of the mouldings. An increase of up to 30% in Young's modulus and 35% in ultimate tensile strength, and a 70-90% increase in strain at peak were gained for the terpolymer (PK) at room temperature, as a result of SCORIM processing. A substantial improvement at 80°C was also recorded for unfilled SCORIM PK mouldings, and is attributed to the pronounced molecular alignment that was induced in SCORIM mouldings, as shown by Debye patterns. It is notable that the SCORIM mouldings of PK exhibit a greater tensile strength at 80°C than the SCORIM mouldings of isotactic polypropylene at 23°C. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 415-430, 1997
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Processing and physical property relationships in injection-molded isotactic polypropylene. 1. Mechanical properties (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 241-263 
    Details
    ISSN: 0887-6266
    Keywords: isotactic polypropylene ; propylene/ethylene copolymers ; injection molding ; SCORIM ; mechanical properties ; impact testing ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aim of the research reported in these two articles was to explore the relationship between processing conditions and the physical properties of different grades of isotactic polypropylene injection moldings and propylene/ethylene copolymers. This first article describes the methods and processing conditions used for molding, together with mechanical test results. Both conventional and shear-controlled orientation injection molding (SCORIM) have been employed for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt, which in turn, facilitates enhanced molecular alignment. SCORIM results in more pronounced molecular orientation than conventional injection molding, which is consistent with the substantial increase in Young's modulus of moldings produced by SCORIM. By controlling the processing parameters it is possible to control and enhance the stiffness without loss of tensile strength. An increase of up to four times in impact strength has been achieved with SCORIM as well as a substantial increase in Young's modulus. The conventional injection moldings containing pronounced molecular orientation exhibited impact resistance well below that for the SCORIM moldings. The mechanical tests carried out at 80°C showed that the high-temperature mechanical properties of all the materials, converted into moldings using SCORIM, exhibited substantial enhancement when compared with moldings of the same material converted by conventional injection molding. © 1997 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Processing and physical property relationships in injection-molded isotactic polypropylene. 2. Morphology and crystallinity (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 265-291 
    Details
    ISSN: 0887-6266
    Keywords: isotactic polypropylene ; injection molding ; SCORIM ; γ-phase ; shish-kebab morphology ; molecular alignment ; crystallinity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A preceding article referred to the processing of various grades of isotactic polypropylene (iPP) and propylene/ethylene copolymers by conventional and shear-controlled orientation injection molding (SCORIM), and considered the mechanical properties of the molded polymers in relation to the processing conditions applied. This article is principally concerned with the morphology and phase relationships that apply in injection-molded iPP. The γ-phase of isotactic polypropylene is reported to occur in moldings with pronounced molecular orientation. The presence of γ-phase in injection moldings is indicative of enhanced Young's modulus, and tensile strength provided that the melt has not been subjected to excessive deformation during processing. The common view that isotactic polypropylene exhibits only α- and β-phases in commercially produced moldings is challenged. SCORIM moldings contain less β-phase than conventional moldings, and exhibit greater overall crystallinity than moldings produced by conventional methods. The difference in the relative proportions of α-, β-, and γ-phases is marked and depends on processing conditions and the molding method. Shear-controlled orientation injection molding (SCORIM) results in more pronounced molecular orientation than conventional injection molding, which is consistent with the substantial increase in Young's modulus of moldings produced by SCORIM. The improved mechanical properties of iPP moldings is attributed to shish-kebab morphology developed by the action of shear to the solidifying melt. A new model is proposed for the oriented region morphology in iPP injection moldings based on the results presented in this article. © 1997 John Wiley & Sons, Inc.
    Additional Material: 39 Ill.
    Type of Medium: Electronic Resource
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