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  • 1
    Publication Date: 1990-09-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 2
    Publication Date: 1981-05-01
    Print ISSN: 0015-7899
    Electronic ISSN: 1434-0860
    Topics: Technology
    Published by Springer
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  • 3
    Publication Date: 1981-02-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 4
    Publication Date: 1997-06-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 275 (1997), S. 511-519 
    ISSN: 1435-1536
    Keywords: Key words Polypropylene ; β-nucleation ; spherulite ; hedrite ; hexagonite ; ovalite ; β to α growth transition ; polarizing light microscopy ; scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  High-temperature crystallization of the β-modification of polypropylene (β-iPP), induced by an active β-nucleating agent, was studied by polarizing light and scanning electron microscopy (SEM). It was established that, in the early stage of crystallization of β-iPP, hedrites were formed as precursors of the spherulitic crystallization. Hedrites seen flat-on are characteristic hexagonal formations (hexagonites) with low birefringence. The central core of hedrites had positive birefringence. Hedrites seen edge-on were rod-like formations with strong negative birefringence which would transform into a radially symmetric spherulitic form through sheaf-like and then oval (ovalite) arrangements. According to the SEM micrographs, hedrites are clusters of multilayer lamellar crystallites. On the surfaces of lamellae hexagonal etch pits appear referring to screw dislocations. They are responsible for branching and proliferation of lamellae. Hedrites may reach considerable sizes (several hundred micrometres) presumably due to a coordinated cooperative growth of lamellae. There is an unequivocal correlation between the character of birefringence and the morphological structure shown by SEM of hexagonites, rods, ovalites and spherulites. It was demonstrated that, at temperatures of isothermal crystallization higher than the critical T(βα) , mixed polymorphic structures of α- and β-modifications were formed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 259 (1981), S. 293-302 
    ISSN: 1435-1536
    Keywords: Spritzgießen ; Struktur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary By injection moulding samples for the tensile test have been prepared from polyethylene. The parameters of injection moulding (melt temperature and mould temperature) have been varied as well as the materials used (different molecular weights and crystalline fractions). Tensile tests have been carried out, the discussion of which has been completed by measurements of density, shrinkage and DSC. The result is, that besides the crystalfraction also a molecular network in the solid state plays an important role on the mechanical behaviour. This is the more the case, the higher the molecular weight and the lower the melt temperature is. The molecular network is responsible for the second yield and if it not exists, also for the magnitude of the tension at the first yield.
    Notes: Zusammenfassung Im Spritzgießverfahren wurden Schulterstäbe für die Zugprüfung aus Polyäthylen hergestellt. Dabei wurde sowohl das Material in Kristallanteil und Molekulargewicht variiert, als auch die Spritzgießbedingungen (Schmelzentemperatur und Werkzeugtemperatur) in systematischer Weise verändert. Es wurden Zugprüfungen durchgeführt, deren Diskussion durch parallele Untersuchungen über Dichte, Schrumpf und DSC der Probestäbe ergänzt wurden. Ergebnis ist, daß außer dem Kristallanteil auch ein Festkörpernetzwerk großen Anteil an den mechanischen Eigenschaften hat. Dies ist um so ausgeprägter, je höher das Molekulargewicht und je niedriger die Spritzgießtemperatur ist. Das molekulare Netzwerk ist verantwortlich für das 2. yield, und falls dies nicht auftritt, auch für die Größe der Streckspannung am 1. yield.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 36 (1990), S. 1675-1684 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Sseigerung der mechanischen Eigenschaften von eigenverstÄrktem Polyethylen (PE-HD) wird durch die Ausbildung einer Shish-Kebab-Struktur erreicht. Die durchgeführten thermo-analytischen Untersuchungen weisen für das hochfeste PEHD gegenüber normalen PE-HD eine um 20
    Notes: Abstract The mechanical properties of the self-reinforced polyethylene increase due to the formation of a shish-kebab structure. Thermal analysis demonstrated that high-strength-PE has a heat deflection temperature 20
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 4087-4097 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Failure mechanisms in randomly reinforced sheet moulding compounds subjected to fatigue testing were studied by relating the changes in characteristic mechanical properties to microscopic changes in the material. It was demonstrated that various mechanisms take place simultaneously to an extent that depends on the local microstructure and strength and that the collective interplay of these mechanisms is responsible for failure. As damage progresses, a uniform pattern of cracks is formed in the matrix, and Mode II fibre/matrix-interfacial failure occurs. The mechanisms concerned can be explained by calculating the forces transmitted between the fibres and the matrix. It was observed that different load amplitudes gave rise to equivalent damage patterns in the material. In the light of this fact and with the aid of the failure mechanisms identified, a method has been devised, by means of which the fatigue life can be estimated of SMC exposed to alternating loads ef any given amplitude.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1147-1154 
    ISSN: 1572-8943
    Keywords: composites ; DMTA ; glass transition temperature ; Round-Robin-test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sensitive method to characterize the thermomechanical behaviour of fiber reinforced composites is the dynamic mechanical thermoanalysis (DMTA) method. A Round-Robin-test with five different institutes was conducted to determine the role of the fiber orientation, processing conditions, test apparatus, the mode of loading, and the matrix materials on the determination of the glass transition temperature (Tg). The result shows that the DMTA is a suitable method to analyze Tg of long fiber composites. However, some major problems have to be taken into consideration: - A direct comparison of results from different DMTA-systems is not possible - The real temperatures in the specimens deviate from the temperatures displayed by the DMTA measuring system - There is no clear and common evaluation method for the glass transition temperature.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1047-1057 
    ISSN: 1572-8943
    Keywords: β-nucleating agent ; β-polypropylene ; crystallization ; degree of crystallinity ; melt enthalpies ; melting ; recrystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ca salts of suberic (Ca-Sub) and pimelic acid (Ca-Pim) were synthesized and used as β-nucleating agents in different grades of isotactic polypropylene (IPP). Propylene homo-, random- and block-copolymers containing these additives crystallize principally in pure β-modification as demonstrated in isothermal and non-isothermal crystallization experiments. Ca-Sub proved the most effective β-nucleating agent known, so far. It broadens the upper crystallization temperature range of pure β-IPP formation up to 140°C. The effect of the additives on the crystallization and melting characteristics of the polymers was studied. The degree of crystallinity of the β-modification was found to be markedly higher than that of α-IPP. High temperature melting peak broadening was first observed and discussed in literary results regarding the same phenomenon for α-IPP.
    Type of Medium: Electronic Resource
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