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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1347-1357 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Variations in PMR-15 composite properties could be due to by-products formed during the polymerization cycle. In order to identify these compounds, various condensation products derived from the three monomeric constituents of the resin: NE, BTDE, and MDA, have been synthesized and fully characterized by spectroscopic methods, mainly by 1H- and 13C-NMR. In these products, one or two MDA amino groups are replaced by amido or imido groups, leading to mono- and di-substituted MDA derivatives. Monosubstituted derivatives were obtained by first protecting one MDA amino group with a terbutoxycarbonyl group (Boc). The MDA's CH2 bridge of these molecules gives rise, in their 1H NMR spectra, to a characteristic resonance singlet, the position of which can be correlated to the nature of the amino substituents through 1H chemical shift increments. The latter provide a useful tool to predict the CH2, shifts in other compounds. Similar substituent increments are proposed for the chemical shifts of the MDA aromatic protons and carbon atoms.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 203-217 
    ISSN: 0887-624X
    Keywords: PMR-15 ; polyimides ; PMR-15 NMR-analyses ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Variations in PMR-15 composites properties could be due to differences in their chemical compositions occurring during the curing cycle. Variations in the composition of the PMR-15 resin were studied for four different curing cycles, to determine the influences of parameters such as the heating rate or the presence of a temperature stage. The resin mixture was sampled at the same four different temperature points in each cycle and analyzed mainly by 1H- and 13C-NMR. Quantitative analysis of the different chemical species were realized by deconvolution of NMR spectra. At a given temperature, the resin contains the same molecules but in proportions which depend on the curing conditions and which reflect differences in the chemical reactivity of the monomeric species. We have precisely defined the temperature ranges at which each of the key reactions (amidization, imidization, exoendo isomerization) occurs. An imine condensation product of NE and MDA has been identified and shown to be present in the resin mixture even at low temperature. As a result of this study, two possible causes of resin alteration during ageing can be put forward: the presence of nonimidized BTDE moieties and the endo-exo isomerization reaction which will result in deformation and, possibly, microcracking, if reticulation of the end-capped nadimides is not total. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1593-1597 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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