Abstract
The previously ignored or unreported impact of regiosomerism within diglycidyl ether of bisphenol F (DGEBF) on its network properties is presented. Routes to the isomers of DGEBF were explored: high-performance liquid chromatography showed good separation of the three isomers [para–para-DGEBF (ppDGEBF), para–ortho-DGEBF (poDGEBF), and ortho–ortho-DGEBF (ooDGEBF)] with small yields; column chromatography gave good separation of pp- + po- from oo-DGEBF but pp-/po- separation was not achieved. Synthesis was optimized to crude yields of 76% for pp-; 87% for po-, and 86% for oo-. Subsequently, crosslinked networks were prepared with meta-xylylenediamine. With increasing ortho content, degradation of chemical resistance and an inherent weakening of the network was observed, that is, glass transition temperature (Tg), beta transition temperature (Tβ), density, crosslink density, and the desorption diffusion coefficient decreased, whereas sorption diffusion coefficient and ultimate solvent uptake increased. This clearly shows that a subtle chemical structure change can significantly impact network performance.
Highlights
Epoxy resins are used in a wide variety of applications, from coatings to composites
This study determines the effect of regioisomerism within diglycidyl ether of bisphenol F (DGEBF) on the chemical performance, in this case the resistance to methanol, as an indicator of chemical performance, which is an indicator of the barrier this network would form
Nuclear magnetic resonance (NMR) spectroscopy shows DER 354 consists of a 3.5:3.2:1 pp/po/oo ratio, determined as per the method described by Domke.[25]
Summary
Epoxy resins are used in a wide variety of applications, from coatings to composites. The low molecular weight components, that is the isomers of diglycidyl ether bisphenol F, present in DER 354 (11 g) were separated by column chromatography, with a column volume of approximately 1400 cm[3]. DER 354 was added to MXDA in a 1:1 stoichiometric ratio of epoxide to amine functional groups, and mixed by hand, using a stirring rod. OoDGEBF was added to MXDA in a 1:1 stoichiometric ratio of epoxide to amine functional groups and mixed by hand, using a stirring rod. Upon reaching a plateau in mass, these samples were removed from the solvent and placed in an oven at 40 °C, and weighed at time intervals until a reasonable plateau was obtained (a return to the original dry mass was only possible upon heating to 120 °C under reduced pressure)
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