Curing and thermomechanical properties of off-stoichiometric anhydride–epoxy thermosets

  • J. M. MoranchoEmail author
  • X. Ramis
  • X. Fernández-Francos
  • J. M. Salla
  • O. Konuray
  • À. Serra


In the present work, we report the preparation and characterization of a new family of thermosets based on off-stoichiometric anhydride–epoxy formulations in the presence of an anionic initiator. Diglycidyl ether of bisphenol A (DGEBA) and hexahydro-4-methylphthalic anhydride (HHMPA) have been used as epoxy and anhydride comonomers, respectively, and 1-methylimidazole (1MI) has been used as anionic initiator. The isothermal curing kinetics and the thermal properties of the stoichiometric and the off-stoichiometric systems have been compared. The kinetics of the isothermal curing has been analyzed by differential scanning calorimetry (DSC) using an isoconversional method and the Šesták–Berggren equation to determine the activation energy, the frequency factor and the reaction orders. The materials obtained were characterized by DSC and dynamic mechanical analysis. Gelation during epoxy–anhydride condensation was determined by thermomechanical analysis. At the same curing temperature, the reaction is faster in the system with excess of epoxy groups. However, the glass transition temperatures of the partially cured stoichiometric system are greater. The gelation time of the off-stoichiometric system is shorter than that of the stoichiometric one. The results indicate that the dual-curing character of off-stoichiometric DGEBA/HHMPA thermosets with 1MI as anionic initiator makes them suitable for multistage curing processes with easy control of degree of cure and material properties in the intermediate stage and enhanced final material properties.


Epoxy networks Isothermal cure Kinetics Gelation 



The authors would like to thank MINECO (Ministerio de Economía y Competividad) and FEDER (Fondo Europeo de Desarrollo Regional) (MAT2017-82849-C2-1-R and MAT2017-82849-C2-2-R) and Generalitat de Catalunya (2017-SGR-77 and Serra Húnter program) for the financial support.


  1. 1.
    Riew CK, Siebert AR, Smith RW, Fernando M, Kinloch AJ. Toughened epoxy resins: performed particles as tougheners for adhesives and matrices. In: Riew CK, Kinloch AJ, editors. Toughened plastics II novel approaches in science and engineering, vol. 252., Advances in chemical seriesWashington: American Chemical Society; 1996. p. 33–44.CrossRefGoogle Scholar
  2. 2.
    Saiki N, Yamazaki O, Ebe K. UV/heat dual-curable adhesive tapes for fabricating stacked packages of semiconductors. J Appl Polym Sci. 2008;108:1178–83.CrossRefGoogle Scholar
  3. 3.
    Kang B-U. Interfacial fracture behavior of epoxy adhesives for electronic components. J Korea Acad Ind Cooper Soc. 2011;12:1479–87.Google Scholar
  4. 4.
    May CA, Tanaka GY. Epoxy resins. In: May CA, editor. Chemistry and technology, chap 1. New York: Marcel Dekker; 1988.Google Scholar
  5. 5.
    Petrie EM. Epoxy adhesive formulations. New York: McGraw-Hill; 2006.Google Scholar
  6. 6.
    Pascault JP, Williams RJJ. Epoxy polymers: new materials and innovations. Weinheim: Wiley-VCH; 2010.CrossRefGoogle Scholar
  7. 7.
    Kinloch AJ, Shaw SJ, Tod DA, Hunston DL. Deformation and fracture behavior of a rubber-toughened epoxy: 1. Microstructure and fracture studies. Polymer. 1983;24:1341–54.CrossRefGoogle Scholar
  8. 8.
    Ho T-H, Wang C-S. Toughening of epoxy resins by modification with dispersed acrylate rubber for electronic packaging. J Appl Polym Sci. 1993;50:477–83.CrossRefGoogle Scholar
  9. 9.
    Mezzenga R, Boogh L, Månson JAE. A review of dendritic hyperbranched polymer as modifiers in epoxy composites. Compos Sci Technol. 2001;61:787–95.CrossRefGoogle Scholar
  10. 10.
    Guo QP, Habrard A, Park Y, Halley PJ, Simon GP. Phase separation, porous structure, and cure kinetics in aliphatic epoxy resin containing hyperbranched polyester. J Polym Sci B. 2006;44:889–99.CrossRefGoogle Scholar
  11. 11.
    Ratna D, Varley R, Simon GP. Toughening of trifunctional epoxy using an epoxy-functionalized hyperbranched polymer. J Appl Polym Sci. 2003;89:2339–45.CrossRefGoogle Scholar
  12. 12.
    He S, Shi K, Bai J, Zhang Z, Li L, Du Z, Zhang B. Studies on the properties of epoxy resins modified with chain-extended ureas. Polymer. 2001;42:9641–7.CrossRefGoogle Scholar
  13. 13.
    Zhou L, Zhang G, Li J, Jing Z, Qin J, Feng Y. The flame retardancy and thermal stability properties of flame-retarded epoxy resins based on α-hydroxyphosphonate cyclotriphosphazene. J Therm Anal Calorim. 2017;129:1667–78.CrossRefGoogle Scholar
  14. 14.
    Mao W, Li S, Yang X, Cao S, Li M, Huang K, Xia J. Preparation of a flame-retardant epoxy curing agent based on castor oil and study on the curing reaction kinetics. J Therm Anal Calorim. 2017;130:2113–21.CrossRefGoogle Scholar
  15. 15.
    Evans D, Canfer SJ. Radiation stable, low viscosity impregnating resin systems for cryogenic applications. Adv Cryog Eng. 2000;46:361–8.Google Scholar
  16. 16.
    Ueki T, Nishijima S, Izumi Y. Designing of epoxy resin systems for cryogenic use. Cryogenics. 2005;45:141–8.CrossRefGoogle Scholar
  17. 17.
    Nishijima S, Honda Y, Okada T. Application of the positron annihilation method for evaluation of organic materials for cryogenic use. Cryogenics. 1995;35:779–81.CrossRefGoogle Scholar
  18. 18.
    Pascault JP, Sautereau H, Verdu J, Williams RJJ. Thermosetting polymers. 1st ed. New York: Marcel Dekker, Inc.; 2002.CrossRefGoogle Scholar
  19. 19.
    Thanki JD, Parsania PH. Dynamic DSC curing kinetics and thermogravimetric study of epoxy resin of 9,9′-bis-(4-hydroxyphenyl)anthrone-10. J Therm Anal Calorim. 2017;130:2145–56.CrossRefGoogle Scholar
  20. 20.
    Foix D, Yu Y, Serra À, Ramis X, Salla JM. Study on the chemical modification of epoxy/anhydride thermosets using a hydroxyl terminated hyperbranched polymer. Eur Polym J. 2009;45:1454–66.CrossRefGoogle Scholar
  21. 21.
    Rocks J, Rintoul L, Vohwinkel F, George G. The kinetics and mechanism of cure of an amino-glycidyl epoxy resin by a co-anhydride as studied by FT-Raman spectroscopy. Polymer. 2004;45:6799–811.CrossRefGoogle Scholar
  22. 22.
    Fernández-Francos X, Santiago D, Ferrando F, Ramis X, Salla JM, Serra À, Sangermano M. Network structure and thermomechanical properties of hybrid DGEBA networks cured with 1-methylimidazole and hyperbranched poly(ethyleneimine)s. J Polym Sci Part B Polym Phys. 2012;50:1489–503.CrossRefGoogle Scholar
  23. 23.
    Leena K, Soumyamol PB, Baby M, Suraj S, Rajeev R, Mohan DS. Non-isothermal cure and decomposition kinetics of epoxy–imidazole systems. J Therm Anal Calorim. 2017;130:1053–61.CrossRefGoogle Scholar
  24. 24.
    Ramis X, Fernández-Francos X, De La Flor S, Ferrando F, Serra À. Click-based dual-curing thermosets and their applications. In: Guo Q, editor. Thermosets: structure, properties and applications, chapter 16. 2nd ed. Amsterdam: Elsevier; 2017.Google Scholar
  25. 25.
    Fernández-Francos X, Konuray AO, Belmonte A, De la Flor S, Serra À, Ramis X. Sequential curing of off-stoichiometric thiol-epoxy thermosets with a custom-tailored structure. Polym Chem. 2016;7:2280–90.CrossRefGoogle Scholar
  26. 26.
    Konuray O, Areny N, Morancho JM, Fernández-Francos X, Serra À, Ramis X. Preparation and characterization of dual-curable off-stoichiometric amine-epoxy thermosets with latent reactivity. Polymer. 2018;146:42–52.CrossRefGoogle Scholar
  27. 27.
    Vyazovkin S, Burnham AK, Criado JM, Pérez-Maqueda LA, Popescu C, Sbirrazzuoli N. ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data. Thermochim Acta. 2011;520:1–19.CrossRefGoogle Scholar
  28. 28.
    Heise MS, Martin GC. Curing mechanism and thermal properties of epoxy-imidazole systems. Macromolecules. 1989;22:99–104.CrossRefGoogle Scholar
  29. 29.
    Flores M, Fernández-Francos X, Ramis X, Serra À. Novel epoxy-anhydride thermosets modified with a hyperbranched polyester as toughness enhancer. Thermochim Acta. 2012;544:17–26.CrossRefGoogle Scholar
  30. 30.
    Ivin KJ. Polymer handbook. Brandrup J, Immergut EH, editors. New York: Wiley; 1975Google Scholar
  31. 31.
    Montserrat S, Flaqué C, Calafell M, Andreu G, Málek J. Influence of the accelerator concentration on the curing reaction of an epoxy-anhydride system. Thermochim Acta. 1995;269(270):213–29.CrossRefGoogle Scholar
  32. 32.
    Santiago D, Fernández-Francos X, Ramis X, Salla JM, Sangermano M. Comparative curing kinetics and thermal-mechanical properties of DGEBA thermosets cured with a hyperbranched poly(ethylenimine) and an aliphatic triamine. Thermochim Acta. 2011;526:9–21.CrossRefGoogle Scholar
  33. 33.
    Morancho JM, Ramis X, Fernández-Francos X, Salla JM, Konuray AO, Serra À. Curing of off-stoichiometric amine-epoxy thermosets. J Therm Anal Calorim. 2018;133:519–27.CrossRefGoogle Scholar
  34. 34.
    Morancho JM, Salla JM. Influence of a carboxyl-terminated modifier (CTBN) on the cure of an epoxy resin. J Non Cryst Solids. 1994;172–174:656–60.CrossRefGoogle Scholar
  35. 35.
    Fernàndez-Francos X, Ramis X, Serra À. From curing kinetics to network structure: a novel approach to the modeling of the network buildup of epoxy-anhydride thermosets. J Polym Sci Part A Polym Chem. 2014;52:61–75.CrossRefGoogle Scholar
  36. 36.
    Tanaka Y, Stanford JL, Stepto R. Interpretation of gel points of an epoxy-amine system including ring formation and unequal reactivity: measurements of gel points and analyses on ring structures. Macromolecules. 2012;45:7197–205.CrossRefGoogle Scholar
  37. 37.
    Mauri AN, Galego N, Riccardi CC, Williams RJJ. Kinetic model for gelation in the diepoxide–cyclic anhydride copolymerization initiated by tertiary amines. Macromolecules. 1997;30:1616–20.CrossRefGoogle Scholar

Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.Thermodynamics Laboratory, Heat Engines Department, ETSEIBUniversitat Politècnica de CatalunyaBarcelonaSpain
  2. 2.Department of Analytical and Organic ChemistryUniversitat Rovira i VirgiliTarragonaSpain

Personalised recommendations