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  • 1
    Electronic Resource
    Electronic Resource
    Chemical structure of networks resulting from curing of N,N-diglycidylaniline-type resins with aromatic amines. IV. Characterization of TGDDM/DDS and TGDDM/DDM networks by high-resolution solid-state 13C-NMR (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3445-3466 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cured N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) based epoxy resins were investigated by high-resolution solid-state 13C-NMR spectroscopy. Associated hardeners were the most commonly used low reactivity 4,4--diaminodiphenylsulphone (DDS), as well as, for comparisons reasons, the higher reactivity 4,4′-diaminodiphenylmethane (DDM) with, in each case, a1 to 1 or 1 to 0.6 epoxy/NH ratio. In order to interpret the spectra, the poorly resolved aliphatic region was decomposed into elementary lines, the structural assignments of which were made using solution 13C-NMR data resulting from a previous model compound study. The main structural feature of all investigated systems is the predominance of small cyclic units resulting from intramolecular reactions of N,N-diglycidylaniline groups. The resins are therefore far less crosslinked that it could be anticipated from the functionality of the reactants. Using the low reactivity DDS still increases this effect, due to a higher proportion of residual non reacted secondary amines. Reducing the initial ratio of hardener could on the contrary lead to a higher proportion of reacted amine function, and thus to a higher crosslinking degree. A qualitative picture of such networks is given at the end.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281221
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical structure of networks resulting from curing of N,N-diglycidylaniline-type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1661-1679 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of model compounds representative of the structures resulting from the first steps of curing in uncatalyzed (or LiClO4-catalyzed) N,N-diglycidylaniline/aromatic amine systems was studied. The results indicate that the intermolecular etherification either does not occur or is very slow under these conditions. Moreover, the latter situation is observed only in the very specific configuration when two hydroxyl groups are very close to each other. From these experiments, it can be inferred that the most likely reactions occurring after the epoxy-primary amine addition in uncatalyzed N,N-diglycidylaniline/aromatic amine systems are the are the epoxy-secondary-amine addition and the cyclization reactions discussed in a previous paper.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280702
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of phenol-formaldehyde resols by gel permeation chromatography (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 1585-1602 
    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 chromatographic analysis of resol solutions in tetrahydrofuran solvent, by means of a set of columns packed with crosslinked polystyrene gels, has been carried out with adequate resolving power for a clear-cut qualitative or semiquantitative differentiation between various types of resols to be practicable. The resulting chromatograms, which show the distribution of different constituents by molecular size, could be interpreted by the use of reference substance and by calibrating the system with a number of compounds of known structures. The method has been used to investigate the way in which various reaction parameters (nature of catalysts, proportion of starting material, treatments undergone by the resols) affect the composition of resols. Different commercial products have been thus characterized. It has also afforded an insight into the progress of the polycondensation reaction as a function of time and helped to state the reactivity of different groups and unblocked ring positions. Thus, an hydroxymethyl group appears to be more reactive in the para than in the ortho position. Otherwise the reactivity of unblocked ring positions would be enhanced by an hydroxymethyl group in the ortho rather than para position.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1972.070160701
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  • 4
    Electronic Resource
    Electronic Resource
    Fourier transform infrared and high-resolution solid-state carbon-13 NMR spectroscopic characterization of cured polystyrylpyridine resins (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1065-1076 
    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: Interesting crosslinked materials possessing good mechanical and thermal properties are obtained by condensation of 2,4,6-trimethylpyridine (collidine) with terephthalic aldehyde in the presence of an acidic catalyst. Fourier transform infrared spectroscopy has been used to follow the kinetics of the chemical reactions involved in the formation of the tridimensional network using aldehyde and ethylene absorption bands. The first steps of the reaction consist in the addition of aldehyde groups on the methyl groups of collidine followed by a dehydration reaction which leads to the formation of ethylenic functions. Crosslinking is obtained by an addition reaction of the methyl groups of collidine on the double bonds created in the first processes. These reactions are strongly dependent on the reaction temperature. Cured resins prepared with different acidic catalysts have been studied by carbon-13 NMR. p-Toluene sulfonic acid leads to residual aldehyde groups in the cured resins whereas no residual aldehyde groups are observed after a relatively short curing time when sulfuric acid is used as the catalyst. The networks created in the two cases are not equivalent and present different mechanical properties.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380607
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  • 5
    Electronic Resource
    Electronic Resource
    Reaction of dicyanates with monophenols  -  modeling of network buildup (1995)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 241-246 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chemical as well as structural modifications of highly branched polycyanurates can be achieved by using the reaction of dicyanates with monofunctional phenols. The key products of this reaction are iminocarbonic esters formed by addition of cyanato and phenolic groups. Two mechanisms are discussed for the second reaction step: an addition of two cyanato groups and an iminocarbonic ester (Route A) and a stepwise addition of iminocarbonic esters (Route B). The crucial difference between the two reactions is the number of abstracted phenolic groups per formation of one triazine ring: one for Route A and three for Route B. The effects of these reaction mechanisms on the gelation behavior and network buildup are studied theoretically with the help of cascade theory as well as experimentally by the reaction of dicyanate of bisphenol A with five different monophenols. The results clearly show that only with a model which is based on Route B can both the critical conversions at the gelation threshold and the gel fractions be modeled quantitatively. Furthermore, phenols with low pKa values were found to have an increased tendency of incorporation into the network.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1995.010460305
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