Reactions of DGEBA epoxy cured with diethanolamine: Isoconversional kinetics and implications to network structure

Journal Article · Mon Nov 19 00:00:00 EST 2018 · Thermochimica Acta

DOI:https://doi.org/10.1016/j.tca.2018.11.013· OSTI ID:1524642

McCoy, John D.  ^[1]; Ancipink, Windy B. ^[1]; Maestas, Salomon R. ^[1]; Draelos, Lara R. ^[1]; Devries, David B. ^[1]; Kropka, Jamie M. ^[2]

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1. New Mexico Institute of Mining and Technology, Socorro, NM (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

The curing of diglycidyl ether of bisphenol A (DGEBA) epoxy with diethanolamine (DEA) is studied. DEA has three reactive groups, a secondary amine hydrogen and two hydroxyls. The secondary amine reacts rapidly, forming an adduct containing tertiary amines, epoxides and hydroxyls. The epoxides and hydroxyls then react in the presence of the amines to crosslink and vitrify the epoxy in the “gelation” reaction. The gelation reaction, the subject of this study, is not simple. The reaction exhibits unusual dependencies on both temperature and degree of cure. Previously, the general mechanisms of this curing process were explored by a number of us. In the present paper, both differential scanning calorimetry (DSC) and isothermal microcalorimetry (IMC) are used to determine a number of characteristic times associated with the reaction. The characteristic times show that the reaction rate has different functional forms at different temperatures and extents of reaction. This results from the reaction rate not depending solely upon the temperature and over-all extent-of-reaction. The concentration of a number of auxiliary reactive species that are generated in the course of the reaction (as well as their mobility and steric hindrance) appear to be key factors in defining the reaction kinetics. The dependence of the final network structure on cure schedule for this type of tertiary amine activated reaction is then discussed in the context of the literature. Lastly, in the Supplementary Material, Kamal-like functions are fit to the isothermal reaction kinetics, with the reader cautioned in applying the functions to non-isothermal cures.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000; NA0003525
• OSTI ID: 1524642
• Alternate ID(s): OSTI ID: 1761217
• Report Number(s): SAND-2019-5970J; 675889
• Journal Information: Thermochimica Acta, Vol. 671, Issue C; ISSN 0040-6031
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Epoxy
DGEBA
Diethanolamine
Tertiary amine