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  • 1
    Electronic Resource
    Electronic Resource
    Buildup of epoxycycloaliphatic amine networks. Kinetics, vitrification, and gelation (1990)
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 725-731 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00205a006
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  • 2
    Electronic Resource
    Electronic Resource
    Gelation in the cyclotrimerization of dicyanates considering substitution effects (1992)
    Springer
    Polymer bulletin 28 (1992), S. 219-225 
    Details
    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 cyclotrimerization of dicyanates to form polycyanurate networks has been analyzed using a pure kinetic model and a combined kinetic-recursive procedure. In both cases substitution effects were considered, i.e. the reactivity of OCN groups pertainning to clusters was assumed lower than the corresponding reactivity of the monomer groups. The gel conversion varied from 1/2 (no substitutions effects) to 2/3 (infinite substitution effects). The evolution of trimer concentration along the reaction constitutes a direct experimental evidence to decide whether the polymerization follows or not an ideal course, described by the mean-field theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299659
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular-mass distributions resulting from the homopolymerization of monoepoxides initiated by tertiary amines (1992)
    Springer
    Polymer bulletin 28 (1992), S. 459-465 
    Details
    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 A reaction scheme based on propagation and intramolecular chain transfer steps is proposed for the anionic homopolymerization of epoxides initiated by tertiary amines. Chain transfer regenerates a living chain and gives a dead chain with terminal vinilydene unsaturations and hydroxy groups. The possibility of generating phenols or substituted phenols is also considered. Molecular-mass distributions were predicted as a function of conversion by both kinetic and Monte Carlo methods. Predictions were compared with experimental results reported in the literature. The evolution of the number-average degree of polymerization could be reasonably predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297340
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  • 4
    Electronic Resource
    Electronic Resource
    Macro- and microgelation in the homopolymerization of diepoxides initiated by tertiary amines (1991)
    Springer
    Polymer bulletin 27 (1991), S. 9-15 
    Details
    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 homopolymerization of an epoxy resin based on diglycidylether of bisphenol A (DGEBA), initiated by benzyldimethylamine (BDMA), was analyzed in the 80°C–140°C temperature range. An heterogeneous network characterized by regions of different glass transition temperature, was obtained. Microgels appeared early in the polymerization while an increase in the reactivity of the second epoxy group of a DGEBA molecule after reaction of the first one, was inferred from size exclusion chromatograms (SEC), obtained at different overall conversions. Both experimental findings were qualitatively explained through an intramolecular chain transfer step that regenerates the initiator in the proximity of pendant epoxy groups. The increase in the polymerization temperature produced an increase in the macroscopic gel conversion and a decrease in the glass transition temperature of regions of high crosslink density. This was ascribed to the increase in the ratio of intramolecular chain transfer over propagation rates, leading to shorter primary chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296318
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  • 5
    Electronic Resource
    Electronic Resource
    Statistical calculations of the network build-up in the postgel stage of A2-cyclotrimerization (1993)
    Springer
    Polymer bulletin 31 (1993), S. 503-509 
    Details
    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 Statistical parameters for the postgel stage of an ideal A2 polycyclotrimerization were derived and compared with the corresponding parameters for an A3 homopolymerization. Both gel fraction and crosslink density increase less with conversion for the former case. This is due to the fact that branching units are present at a constant concentration from the beginning of the A3 homopolymerization, but show a linear increase with conversion, from zero to the maximum value, for the A2 polycyclotrimerization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329889
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  • 6
    Electronic Resource
    Electronic Resource
    Relationships between glass transition temperature and conversion (1990)
    Springer
    Polymer bulletin 24 (1990), S. 115-121 
    Details
    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 Couchman approach to the expression of the compositional variation of glass transition temperature (or the Di-Benedetto equation) can be used to evaluate the effect of molecular weight on Tg for a stepwise linear polymer. An expression for the KL constant in the Fox-Flory equation is proposed. It is also possible to estimate the TgL corresponding to the hypothetical linear structure defined in a three-dimensional network. For different epoxy-diamine systems, we have found a good concordance with the results obtained previously using an additive law.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298330
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  • 7
    Electronic Resource
    Electronic Resource
    Nichtkatalytische Gas-Feststoff-Reaktion. Chromoxid-Katalysator bei der Methanol-Synthese (1977)
    Springer
    Colloid & polymer science 255 (1977), S. 612-612 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01549793
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  • 8
    Electronic Resource
    Electronic Resource
    Toughened-hybrid epoxies: influence of the rubber-phase morphology on mechanical properties (1994)
    Springer
    Journal of materials science 29 (1994), S. 2481-2486 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00363443
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  • 9
    Electronic Resource
    Electronic Resource
    Some aspects of curing novolac with hexamethylenetetramine (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 311-318 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Curing novolac with hexamethylenetetramine in closed molds at T = 190°C was studied. Cured products were examined with the following experimental techniques: sol fraction determination, % N fixed in sol and gel fractions, and IR spectra. The fraction of fixed N decreased from 1 to 0.5 when the hexa mass fraction was increased from 0 to 0.3 in the mixture with novolacs. A segregation of the fixed N in the sol fraction was observed. Azomethine derivatives were present, their amounts increasing with the hexa mass fraction. Curing was described by a reaction scheme similar to the one derived from studies with model phenols. A simplified scheme was adequate for the prediction of the minimum hexa amount necessary to gel the system at full conversion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.170200205
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  • 10
    Electronic Resource
    Electronic Resource
    On the curing kinetics of unsaturated polyesters with styrene (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 485-499 
    Details
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The curing kinetics of a general purpose unsaturated polyester (UP) with styrene was studied by differential scanning calorimetry and dielectric capacitance measurements. Benzoyl peroxide was used as initiator. Results showed that there is a complete change in the phenomenological kinetics, in different temperature ranges. At low temperatures (70-90°C), the rate went through a maximum and then showed a first-order decay. At high temperatures (100-160°C) a second-order kinetics was suitable for all the conversion range. At T 〉 160°C another mechanism took place when the initiator amount was less than a critical value. From the changes in the dielectric capacitance it was inferred that the conversion rate of UP unsaturations followed a first-order decay after a certain conversion, with an activation energy close to values reported for diffusion of UP radicals. Possible free radical mechanisms accounting for experimental observations are discussed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070280205
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