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  • 1
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The thermal and viscoelastic behaviour of several copolymers of propene and 1-hexene have been studied in a wide range of compositions. The samples were prepared with a Ziegler-Natta catalyst with both internal and external donors. A significant amount of crystallinity has been found for the sample with a comonomer content as high as 19 mol %. The dynamic mechanical results show a considerable decrease of the storage modulus in the copolymers in relation to that of iPP. A single relaxation, corresponding to the glass transition, has been found in all the samples. Only the copolymer with the highest hexene content seems to display the beginning of another relaxation at low temperature.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Propylene was polymerized in the presence of the isospecific Et(Ind)2ZrCl2 (Et: ethylene, Ind: indenyl) and the aspecific (Ind)2ZrCl2 complexes in solution and anchored to SiO2 and SiO2/MAO (MAO: methylaluminoxane) supports. From the stereochemical analysis of the polypropene samples obtained it can be deduced that (i) the same active species is formed when a metallocene is in solution and when it is anchored to the SiO2/MAO support and (ii) a completely different active species is formed when the metallocene is anchored to the silica. The fact that both systems Et(Ind)2ZrCl2—SiO2 and (Ind)2ZrCl2—SiO2 produce the same prevailingly isospecific polymer suggests that only isospecific centers are formed in this case, independently of the metallocene stereochemical structure.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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