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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 2481-2486 
    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 A toughened-epoxy polymer based on diglycidylether of bisphenol A (DGEBA) cured with ethylenediamine (EDA) and modified with a rubber based on an epoxy-terminated acrylonitrile-butadiene random copolymer (ETBN), exhibited different morphologies depending on the rubber content. Up to 10% rubber, the morphology consisted of a random dispersion of spherical domains rich in rubber, while at 15% rubber, large and irregular domains were present, turning into a co-continuous structure at 20% rubber. Mechanical properties (elastic modulus, uniaxial compression yield stress, critical stress intensity factor, K IC and strain energy release rate, G IC) of the toughened epoxies and hybrid-particulate materials containing glass beads, were analysed. The best mechanical properties were exhibited by hybrids with a random dispersion of rubbery domains in the epoxy matrix. The presence of large and irregular domains or co-continuous structures led to materials with poor mechanical properties.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 30 (1995), S. 2446-2454 
    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 The influence of annealing temperature on the fracture behaviour of a commercial extrusion-grade isotactic polypropylene was studied. Fracture mechanics analysis was carried out at room temperature and at a low crosshead speed underJ-controlled conditions. Parameters characterizing fracture initiation,J IC, and crack propagation,T M, were determined. Some thermal treatments induced “ductile instability” after a certain amount of crack extension while others strongly enhanced the fracture toughness parameters and promoted completely stable behaviour. Aiming to correlate mechanical properties with the supermolecular structure, the different morphologies induced by thermal treatments were studied by differential thermal analysis. In addition, a qualitative fracture surface analysis was carried out by SEM. Craze formation appeared to be the principal plastic deformation mechanism present. The degree of crystallinity and the degree of interconnection related to the thermal treatment the sample had undergone, are the main structural factors controlling fracture performance.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1245-1248 
    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: The performance of a laboratory packed-column for the manufacture of urea-formaldehyde (UF) concentrates is analyzed. Gaseous formaldehyde was generated by the thermal decomposition of paraformaldehyde in a carrier nitrogen stream. The UF solution was continuously recirculated through a glass column filled with Raschig rings. No pH control was necessary when the operation was started using a solution with a F/U molar ratio higher than 3.5 to 4. Otherwise, insoluble resins appeared during the operation. The formaldehyde absorption rate was controlled by the gas phase resistance. The vapor composition in equilibrium with a typical UF concentrate is provided as a function of temperature.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1503-1511 
    ISSN: 0887-6266
    Keywords: glass transition of non-stoichiometric epoxy/amine networks ; epoxy/amine non-stoichiometric networks, Tg of ; networks of non-stoichiometric epoxy/lamine, Tg of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Glass transition temperatures (Tg) of nonstoichiometric epoxy-amine networks based on the diglycidylether of bisphenol A (DGEBA), are analyzed in terms of the network structure. In most cases reasonable predictions of Tg can be made using an empirical equation reported by L. E. Nielsen together with the experimental Tg value of the stoichiometric network and statistical calculations of the concentration of elastic chains. It is stated that in these rigid networks the concentration of elastic chains is the main structural factor associated to the variations of Tg with stoichiometry. For flexible networks based on the diglycidylether of butanediol (DGEBD), the effect of elastic chains on the Tg value is much less significant.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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