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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 582-585 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Deep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: polypropylene ; spherulite ; cocrystallization ; lamellae ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: During spherulitic crystallization of polymers, there is a tendency for low molecular weight and other less crystallizable entities to be rejected from the body of the spherulites. This rejection process causes a segregation of these species to those areas where spherulites impinge. As a result of this segregation, lamellar and spherulite boundaries have a tendency to become weak, often resulting in premature mechanical failure. The objective of this work, anthropomorphically speaking, is to develop a melt miscible blend system in which a propylene copolymer “fools” a polypropylene homopolymer into rejecting the copolymer to the spherulite boundaries as an impurity. However, once the copolymer arrives at these boundaries, the copolymer subsequently connects adjacent spherulites through cocrystallization of the propylene copolymer segments. It was found that addition of either a random ethylene-propylene copolymer or an isotactic-atactic block copolymer was able to yield the desired effect. Cocrystallization was confirmed by calorimetry, and segregation of copolymer and subsequent reinforcement at the spherulite boundaries was directly observed microscopically. Using this approach, toughness was increased with little loss in stiffness. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2047-2056, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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