Quantitative Characterization of Solid Epoxy Resins Using Comprehensive Two Dimensional Liquid Chromatography Coupled with Electrospray Ionization-Time of Flight Mass Spectrometry (original) (raw)
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Journal of Applied Polymer Science, 1975
The molecular weight distributions as measured by gel permeation chromatography of solid epoxide resins made by the direct addition of epichlorohydrin to bisphenol A (the " t d y " process) and by the reaction of low molecular weight liquid epoxide resins whose main constituent is the diglycidyl ether of bisphenol A with bisphenol A (the "advance ment" process) have been compared with the theoretical distribution calculated by the application of Flory statistia. The model used for predicting the molecular weight distribution has been shown to be too simple to describe the real size distribution of these resins. For resins prepared by the "taffy" process, incompleteneas of reaction, the presence of monofunctional epoxides, and the possibility of branching reactions through the epoxide-hydroxyl reaction lead to a distribution that more nearly resembles one calculated for a resin having a higher epoxide value than that actually measured. In the case of resins prepared by the "advancement" process, the presence of small amounts of the higher oligomeric diepoxides and monofunctional epoxides in the starting material used for the synthesis lead to complex molecular weight distributions that are not easy to deduce theoretically. The experimentally determined molecular weight distributions for the higher molecular weight epoxide resins (epoxide value <2 eq/kg) made by the "advancement" process resemble more nearly those calculated for resins having lower epoxide values than those actually measured.
Pyrolysis/mass spectrometry and pyrolysis/gas chromatography/mas spectrometry analysis of polymers
Rapid Communications in Mass Spectrometry, 1991
The potential of pyrolysis/gas chromatography/mass spectrometry in the study of the chemical composition and structure of polymers and copolymers is demonstrated, and results obtained on polysilane copolymers, phenolformaldehyde polycondensates and diol modified epoxy resins are presented. Temperatureltime-resolved pyrolysis mass spectrometry, carried out in the direct inlet of a mass spectrometer, revealed the presence of monomer and oligomer residues and of volatile additives in epoxy resin samples. Basic information was also obtained on the mechanism of thermal decomposition reactions in polysilane copolymers and diol modified epoxy resins.
Dinâmica Molecular Reativa Da Abertura Do Anel Epóxi Em Reações Com Poliamina
Química Nova
Recebido em 09/09/2019; aceito em 03/02/2020; publicado na web em 06/04/2020 REACTIVE MOLECULAR DYNAMICS OF THE EPOXY RING-OPENING IN POLYAMINE REACTIONS. The molecular dynamics simulations were used to study the epoxy ring-opening in the determination of kinetic parameters, with a temperature range from 1500 to 2500 K in a 20 x 20 x 20 Å unit cell containing 15 molecules of C 2 H 4 O (ethylene oxide) and 35 molecules of CH 6 N 2 (methanediamine). The activation energy values for epoxy and diamine was 66 and 92 kJ mol-1 , respectively. The simulation showed epoxy ring breakage in some of the molecules, but mainly the release of ammonia by diamine. It was observed that the activation energy involved in diamine consumption for ammonia formation is higher than for the epoxy ring opening. The results of the epoxy ring-opening study show that the polymerization occurs slowly, which leads to high computational simulation values.
Spectroscopic and quantitative chemometric analysis of the epoxidised oil/amine system
Journal of Near Infrared Spectroscopy, 2010
The competitiveness between the oxirane functional group and the ester functional group present in a derivative epoxidised oil was studied by monitoring a model system which involved epoxidised oleic oil and aniline (1 : 1). The reaction was carried out under isothermal conditions at 95°C and monitored in situ by near infrared (NIR) spectroscopy. This system is taken as a model of the curing process in the manufacture of epoxy resins from triglycerides and diamines. Conventional spectroscopic analysis and generalised two-dimensional NIR correlation spectroscopy analysis have led to the conclusion that, even though the formation of secondary amines by ring-opening of the oxirane group as a consequence of the nucleophilic attack of the aniline is prior, the formation of amides as a consequence of the ester group reactivity is a competitive reaction. The presence of the two aforementioned reactions is also in accordance with the significant number of factors found when the spectra data matrix was analysed by evolving factor analysis. By applying multivariate curve resolution-alternating least squares to the NIR spectra obtained during the reaction, it has been possible to obtain the concentration and the spectra profiles of each chemical species involved in the reaction. The performance of the model was assessed by two parameters: alternating least squares lack of fit (lof = 1.67 %) and explained variance (R 2 = 99.68%). The recovered spectra of the generated products have the characteristic bands associated with the two postulated reactions.
Analytica Chimica Acta, 2007
This paper reports the validation of the results obtained by combining near infrared spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS) and using high performance liquid chromatography as a reference method, for the model reaction of phenylglycidylether (PGE) and aniline. The results are obtained as concentration profiles over the reaction time. The trueness of the proposed method has been evaluated in terms of lack of bias. The joint test for the intercept and the slope showed that there were no significant differences between the profiles calculated spectroscopically and the ones obtained experimentally by means of the chromatographic reference method at an overall level of confidence of 5%. The uncertainty of the results was estimated by using information derived from the process of assessment of trueness. Such operational aspects as the cost and availability of instrumentation and the length and cost of the analysis were evaluated. The method proposed is a good way of monitoring the reactions of epoxy resins, and it adequately shows how the species concentration varies over time.
Macromolecules, 1997
The chemical substitution of amine nitrogens in cured, 15 N-labeled epoxy resins has been determined by a combination of rotational-echo double-resonance 13 C NMR and dipolar rotational spinecho 15 N NMR. Amine-nitrogen substitution is at least 90% (that is, no more than 10% of all nitrogens have a directly bonded hydrogen) for resins formed from stoichiometric amounts of epoxide and either hexamethylenediamine or a 1:3 molar mixture of hexamethylenediamine and hexylamine. This direct measure of curing and cross-linking is consistent with indirect Fourier-transform infrared estimates of curing based on the disappearance of the deformation band of the epoxide ring.
Location of the Antiplasticizer in Cross-Linked Epoxy Resins by2H,15N, and13C REDOR NMR
Macromolecules, 1998
Carbon-13 rotational-echo double-resonance (REDOR) NMR with 15 N or 2 H dephasing, combined with 15 N REDOR NMR with 13 C dephasing, has been obtained for a fully cross-linked epoxy resin prepared from a nominally uniform mixture of two parts of diglycidyl ether of Bisphenol A, one part of hexamethylenediamine, and 19% (by weight) antiplasticizer made from a carbonyl-13 C-labeled aromatic acetamide. The antiplasiticizer contains the hydroxypropyl ether moiety of the epoxy repeat unit. A partially cross-linked resin was formed from five parts of epoxide, one part of hexamethylenediamine, three parts of hexylamine, and 19% (by weight) antiplasticizer. Labels were introduced into the resin by replacing both methyl groups of the isopropylidene moiety of Bisphenol A with CD3 groups and by using [ 15 N2]hexamethylenediamine and [ 15 N]hexylamine (and their unlabeled counterparts) in various combinations. The antiplasticizer 13 C-carbonyl carbon is 4.9 ( 0.5 Å from an amine 15 N (with no preference for free or cross-linked sites) and 6.7 ( 1 Å from a quaternary carbon of the isopropylidene moiety.
Investigation of 4,5-epoxymorphinan degradation during analysis by HPLC
Journal of Pharmaceutical and Biomedical Analysis, 2002
Compounds of the 4,5-epoxymorphinan series have been shown to degrade in solution to the corresponding 2,2%-dimers when stored in amber glass HPLC vials. A colorant in the glass has been shown to catalyze the degradation. Although amber glass is routinely used to protect solutions from light degradation, it should not be used without evaluating its effect on sample stability.