Etude des prépolymères époxydes par chromatographie et ¹H NMR à 350 MHz

Abstract

The epoxy resins (DGEBA) obtained from 4,4'-isopropylidendiphenol (bisphenol A) and 1 -chloru-2,3-epoxypropane (epichlorohydrin) and synthetized by the "taffy" process were found to consist of oligomers. The composition of prepolymers could be deduced from gel permeation chromatography (GPC), and particularly by high pressure liquid chromatography (HPLC). In the more resolved HPLC spectrum each oligomer was found to be accompanied by satellite: peaks. The functionality of the prepolymers, determined by 'H NMR spectroscopy and cryometric or vapour pressure osmometric measurements was found to be less than two. These phenomena are due to the existence of abnormal chain ends having no epoxy group. The structure of the main components separated by preparative GPC was studied by 'H NMR. For the impurities, the two identified structures of chain ends are primary and secondary alcohol functions. Finally the compositions of three DGEBA were determined.

Synthesis and properties of biobased epoxy resins. part 1. Glycidylation of flavonoids by epichlorohydrin

“…All of these by-products have also been observed in the case of BPA glycidylation. 33,34 The slight difference in the average number of methyloxirane functions per resorcinol ring given by the chemical assay (1.5) and calculated from NMR data (1.8) may be explained by the presence of residual salts that were not removed in the work up of the reaction: these residual salts are taken into account in weighting the sample for chemical assay of methyloxirane functions whereas, in NMR, only the protonated species are used for the ratio calculation.…”

Development of Biobased Epoxy Matrices for the Preparation of Green Composite Materials for Civil Engineering Applications

“…The chromatograms of the three compounds are presented in Figure . The chromatogram of the biobased DGEBA is identical to that of a typical DGEBA of similar EEW; the main peak at an elution volume of 24.8 mL is due to the pure monomer ( n = 0) with a molar mass of 340 g mol −1 , two other small peaks at 22.13 and 20.9 mL are due to some oligomers ( n = 1 and n = 2, respectively) of higher molar mass, and the peak at 23.6 mL corresponds to the presence of different terminal groups such as primary and secondary alcohols . The SPGE chromatogram is very different; it shows a broad peak centered at 21.56 mL and a few small peaks at higher elution volumes.…”

Determination of the formulation and curing conditions of thermosetting epoxy resins for optimizing their properties and future use in gelcasting process

“…It is known from the literature that this reaction can lead to the formation of various by-products resulting from polyaddition of ECH, formation of β-chlorohydrin, α-glycol, or homopolymerization of the resin. 34 The byproducts may also be residual diol or diphenol, but also mono-epoxide of the diol. However, both RDGE and BDGE grades available from CVC Thermoset Specialties were claimed to be difunctional epoxy.…”