Cure mechanisms of diglycidyl ether of bisphenol A (DGEBA) epoxy with diethanolamine
| Autor: | N. Fredj, Jamie Michael Kropka, John D. McCoy, Caitlyn M. Clarkson, Lebelo Hailesilassie, Nicholas Henry Giron, Windy B. Ancipink, Mathias C. Celina |
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| Rok vydání: | 2016 |
| Předmět: |
Isothermal microcalorimetry
Diethanolamine Diglycidyl ether Polymers and Plastics Tertiary amine Organic Chemistry Epoxide 02 engineering and technology Epoxy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Autocatalysis Chemical kinetics chemistry.chemical_compound chemistry visual_art Polymer chemistry Materials Chemistry visual_art.visual_art_medium 0210 nano-technology |
| Zdroj: | Polymer. 105:243-254 |
| ISSN: | 0032-3861 |
| DOI: | 10.1016/j.polymer.2016.10.028 |
| Popis: | When diethanolamine (DEA) is used as a curative for a DGEBA epoxy, a rapid “adduct-forming” reaction of epoxide with the secondary amine of DEA is followed by a slow “gelation” reaction of epoxide with hydroxyl and with other epoxide. Through an extensive review of previous investigations of simpler, but chemically similar, reactions, it is deduced that at low temperature the DGEBA/DEA gelation reaction is “activated” (shows a pronounced induction time, similar to autocatalytic behavior) by the tertiary amine in the adduct. At high temperature, the activated nature of the reaction disappears. The impact of this mechanism change on the kinetics of the gelation reaction, as resolved with differential scanning calorimetry, infrared spectroscopy, and isothermal microcalorimetry, is presented. It is shown that the kinetic characteristics of the gelation-reaction of the DGEBA/DEA system are similar to other tertiary-amine activated epoxy reactions and consistent with the anionic polymerization model previously proposed for this class of materials. Principle results are the time-temperature-transformation diagram, the effective activation energy, and the upper stability temperature of the zwitterion initiator of the activated gelation reaction. It is established that the rate of epoxide consumption cannot be generically represented as a function only of temperature and degree of epoxy conversion. The complex chemistry active in the material requires specific consideration of the dilute intermediates in the reaction sequence in order to define a model of the reaction kinetics applicable to all time-temperature cure histories. |
| Databáze: | OpenAIRE |
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