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Abstract  

Differential scanning calorimetry (DSC) was applied to study the cure kinetics of an epoxy system containing both tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) and a multifunctional Novolac glycidyl ether resin, cured with 4,4′-diaminodiphenylsulfone (DDS). The experimental data were analyzed in terms of a mechanistic model proposed by Cole, which includes the etherification reaction. The kinetics can be completely described in terms of three rate constants, which obey the Arrhenius relationship. This model gives a good description of the cure kinetics up to the onset of vitrification. The effect of diffusion control was incorporated to describe the cure in the later stages. By combining the model and a diffusion factor, it was possible to predict the cure kinetics over the whole range of conversion, including an analysis of the evolution of different chemical species during the curing process. Good agreement with the experimental DSC data was achieved with this mechanistic model over the whole range of cure when the etherification reaction was assumed to be of first order with respect to the concentrations of epoxide groups, hydroxy groups, and the tertiary amine groups formed in the epoxide amine reaction.

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Summary A kinetic study of cure kinetics of epoxy resin based on a diglycidyl ether of bisphenol A (DGEBA), with poly(oxypropylene) diamine (Jeffamine D230) as a curing agent, was performed by means of differential scanning calorimetry (DSC). Isothermal and dynamic DSC characterizations of stoichiometric and sub-stoichiometric mixtures were performed. The kinetics of cure was described successfully by empirical models in wide temperature range. System with sub-stoichiometric content of amine showed evidence of two separate reactions, second of which was presumed to be etherification reaction. Catalytic influence of hydroxyl groups formed by epoxy-amine addition was determined.

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Journal of Thermal Analysis and Calorimetry
Authors: Silvia Prolongo, M. Burón, A. Salazar, A. Ureña, and J. Rodríguez

Abstract  

Blends based on epoxy resins and a random copolymer, poly(styrene-co-allylalcohol) (PS-co-PA) were studied, analysing the effect of epoxy nature. The epoxy cross-linking reaction was carried out by homopolymerisation, using an imidazole as initiator, and by addition of several amine hardeners. The imidazole acts as initiator of anionic epoxy etherification and as catalyser of epoxy-hydroxyl reaction. Important differences were observed on the network structure and phase behaviour of blends depending on the nature of epoxy matrix. These cause that the blends present different morphologies and different dynamic mechanical properties.

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By means of DSC, DTA, TG and NMR it was established that the process of cure of epoxy resins induced by aqueous solutions of heteropolyacids consists of two stages, the first one being connected with a catalytic interaction between oligomer and water, and the second one with epoxy-hydroxyl etherification. Analysis of kinetic data shows that the first reaction is diffusion controlled, the second process can be described by pseudo-first order kinetics with activation energy about 40 kJ/M.

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Journal of Flow Chemistry
Authors: Viktor Misuk, Andreas Mai, Yuning Zhao, Julian Heinrich, Daniel Rauber, Konstantinos Giannopoulos, and Holger Löwe

Fast mixing is essential for many microfluidic applications, especially for flow at low Reynolds numbers. A capillary tube-in-tube coaxial flow setup in combination with a glass microreactor was used to produce immiscible multiphase segments. These double emulsion segments are composed of an organic solvent as the shell (outer) phase and a completely fluorinated liquid (Fluorinert® FC-40) as the core (inner) phase. Due to the higher density of the core droplets, they are responsive to changing their position to the force of gravity (g-force). By gently shaking or jiggling the reactor, the core drop flows very fast in the direction of the g-field without leaving the shell organic phase segment. Furthermore, by shaking or jiggling the reactor, the inner droplet moves along the phase boundary of the shell segment and continuous phase. Computational fluid dynamics (CFD) calculations show an enhancement of the internal circulations, i.e., causing an exceptional mixing inside of the shell segment. For reactions which are limited by mass transfer, where the conversion significantly increases with improved mixing, these recirculation zones are decisive because they also accelerate the mixing process. With a common phase-transfer catalytic (PTC) etherification of phenol with dimethyl sulphate, a remarkable increase of yield (85% gas chromatography [GC]) could be achieved by applying active mixing within a segment in continuous flow.

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-linking of the modified linseed oil can proceed via two principal pathways: esterification and etherification [ 20 ]. The reaction of the alkoxide anion at the epoxy backbone with an anhydride molecule leads to formation of a monoester, which in turn may

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1 ). The deactivation mechanism of the catalysts, CaO, Ca(OH) 2 and Ca(OCH 3 ) 2 , is summarized in Scheme 1 . From the deactivation mechanism of the alkali solid catalysts, it can be seen that the etherification of glycerol and the

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–1869 “A continuous flow strategy for the coupled transfer hydrogenation and etherification of 5-(hydroxymethyl)furfural using Lewis acid zeolites” J. D. Lewis, S. Van de Vyver, A. J. Crisci, W. R. Gunther, V. K. Michaelis, R. G. Griffin, Y. Roman

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and an electronic displacement from this group in the direction of the double bound which causes that the C atom with the –OH group is more electronegative and therefore more susceptible to oxidation. The studies also presented that the etherification

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-Catalyzed Ullmann Etherification Reaction: A μ 2 -Process ” F. Benaskar , N. G. Patil , E. V. Rebrov , A. Ben-Abdelmoumen , J. Meuldijk , L. A. Hulshof , V. Hessel ,* J. C. Schouten ChemSusChem 2013 , 6 , 353 – 366

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