CEAS Aeronautical Journal

, Volume 9, Issue 1, pp 235–248 | Cite as

Novel epoxy prepreg resins for aircraft interiors based on combinations of halogen-free flame retardants

  • Thomas Neumeyer
  • Anika Bauernfeind
  • Verena Eigner
  • Claudia Mueller
  • Kerstin Pramberger
  • Volker AltstaedtEmail author
Original Paper


Heat release and smoke emission are crucial characteristics regarding the burning behaviour of materials used inside the cabin of a commercial aircraft. In this work, an approach to enhance these properties of epoxy novolac-based resin formulations is presented. The phosphorus-based flame retardant DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) is used in combination with inorganic flame retardants to merge different flame-retarding mechanisms. The effects of the single flame-retarding components on the fire behaviour of the neat epoxy resin are investigated at first by cone calorimeter measurements. Following, the interactions of combining (1) DOPO and ATH and (2) DOPO and boehmite are studied systematically. It is shown that the sole DOPO modification effectively reduces the heat release by gas phase mechanisms, but at the same time increases the smoke production tremendously due to the flame inhibition and the resulting incomplete combustion. By adding inorganic flame retardants, this increase in smoke release can be compensated for. Furthermore, the aforementioned combination of DOPO and ATH leads to a synergistic effect on time to ignition. Fire testing on sandwich structures, consisting of prepreg face sheets based on the resin systems described before, reveals that the relevant characteristics to meet fire safety requirements for aircraft interiors can be fulfilled. Additionally, the influence of the modifiers on the thermal and mechanical properties of the cured resins are presented and discussed. The inorganic flame retardants significantly increase the fracture toughness of the originally rather brittle epoxy novolac resins from around 0.5 MPa m1/2 up to approximately 0.8 MPa m1/2 for the boehmite type used and up to 1.0 MPa m1/2 for ATH at a filler loading of 33.3 wt% in both cases.


Prepreg Epoxy Flame retardancy Halogen free Cone calorimetry 



The authors are grateful to the Federal Ministry for Economic Affairs and Energy for the financial support through LuFo and to the German Research Foundation (DFG) for support within the Collaborative Research Center 840 (SFB 840).


  1. 1.
    Heth, J.: From art to science: a prepreg overview. High Perform. Compos. 8, 32–36 (2000)Google Scholar
  2. 2.
    Mouritz, A.P., Gibson, A.G.: Fire Properties of Polymer Composite Materials. Springer, Dordrecht (2006)Google Scholar
  3. 3.
    Taylor, J.G.: Composites. In: Pilato, L.A. (ed.) Phenolic Resins: A Century of Progress, pp. 263–306. Springer, Heidelberg (2010)CrossRefGoogle Scholar
  4. 4.
    Pham, H.Q., Marks, M.J.: Epoxy resins. In: Mark, H.F. (ed.) Encyclopedia of Polymer Science and Technology, pp. 678–804. Wiley, New York (2004)Google Scholar
  5. 5.
    Levchik, S.V., Weil, E.D.: Thermal decomposition, combustion and flame-retardancy of epoxy resins—a review of the recent literature. Polym. Int. (2004). Google Scholar
  6. 6.
    Bourbigot, S., Le Bras, M.: Flame retardants. In: Troitzsch, J. (ed.) Plastics Flammability Handbook, pp. 133–157. Carl Hanser, Munich (2004)CrossRefGoogle Scholar
  7. 7.
    Georlette, P., Simons, J.: Halogen-containing fire-retardant compounds. In: Grand, A.F., Wilkie, C.A. (eds.) Fire Retardancy of Polymeric Materials, pp. 245–284. Marcel Dekker Inc., New York (2000)Google Scholar
  8. 8.
    Levchik, S., Weil, E.: A review of recent progress in phosphorus-based flame retardants. J. Fire Sci. (2006). Google Scholar
  9. 9.
    Kim, J., Yoo, S., Bae, J.-Y., Yun, H.-C., Hwang, J., Kong, B.-S.: Thermal stabilities and mechanical properties of epoxy molding compounds (EMC) containing encapsulated red phosphorous. Polym. Degrad. Stab. (2003). Google Scholar
  10. 10.
    Braun, U., Balabanovich, A.I., Schartel, B., Knoll, U., Artner, J., Ciesielski, M., Döring, M., Perez, R., Sandler, J.K.W., Altstädt, V., Hoffmann, T., Pospiech, D.: Influence of the oxidation state of phosphorus on the decomposition and fire behaviour of flame-retarded epoxy resin composites. Polymer (2006). Google Scholar
  11. 11.
    Green, J.: Phosphorus-containing flame retardants. In: Grand, A.F., Wilkie, C.A. (eds.) Fire Retardancy of Polymeric Materials, pp. 147–170. Marcel Dekker Inc., New York (2000)Google Scholar
  12. 12.
    Weil, E.D., Levchik, S.V.: Flame Retardants for Plastics and Textiles. Carl Hanser, Munich (2009)CrossRefGoogle Scholar
  13. 13.
    Döring, M., Diederichs, J., Bykov, Y.: Innovative Flame Retardants in E&E Applications, pinfa—Phosphorus. Inorganic and Nitrogen Flame Retardants Association, Brussels (2010)Google Scholar
  14. 14.
    Seibold, S.: Halogenfrei flammgeschützte Epoxidharzsysteme auf der Basis von Präformulierungen [Halogen-free flame retardant epoxy resins based on preformulations]. PhD-Thesis, Ruprecht-Karls-Universität, Heidelberg (2007)Google Scholar
  15. 15.
    Sauerwein, R.: Mineral filler flame retardants. In: Morgan, A.B., Wilkie, C.A. (eds.) Non-Halogenated Flame Retardant Handbook, pp. 75–141. Scrivener Publishing, Beverly (2014)CrossRefGoogle Scholar
  16. 16.
    Horn, W.E.: Inorganic hydroxides and hydrocarbonates: their function and use as flame-retardant additives. In: Grand, A.F., Wilkie, C.A. (eds.) Fire Retardancy of Polymeric Materials, pp. 285–352. Marcel Dekker Inc., New York (2000)Google Scholar
  17. 17.
    Hull, T.R., Witkowski, A., Hollingbery, L.: Fire retardant action of mineral fillers. Polym. Degrad. Stab. (2011). Google Scholar
  18. 18.
    Rakotomalala, M., Wagner, S., Döring, M.: Recent developments in halogen free flame retardants for epoxy resins for electrical and electronic applications. Materials (2010). Google Scholar
  19. 19.
    Döring, M., Ciesielski, M., Heinzmann, C.: Synergistic flame retardant mixtures in epoxy resins. In: Morgan, A.B., Wilkie, C.A., Nelson, G.L. (eds.) Fire and Polymers VI: New Advances in Flame Retardant Chemistry and Science, pp. 295–309. American Chemical Society, Washington (2012)Google Scholar
  20. 20.
    Pascault, J.-P., Williams, R.J.J.: General concepts about epoxy polymers. In: Pascault, J.-P., Williams, R.J.J. (eds.) Epoxy Polymers, pp. 1–12. WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (2010)CrossRefGoogle Scholar
  21. 21.
    Neumeyer, T., Staudigel, C., Bonotto, G., Altstaedt, V.: Influence of an imidazolium salt on the curing behaviour of an epoxy-based hot-melt prepreg system for non-structural aircraft applications. CEAS Aeronaut. J. (2015). Google Scholar
  22. 22.
    Neumeyer, T., Bonotto, G., Kraemer, J., Altstaedt, V., Doering, M.: Fire behaviour and mechanical properties of an epoxy hot-melt resin for aircraft interiors. Compos. Interfaces (2013). Google Scholar
  23. 23.
    Treloar, L.R.G.: The physics of rubber elasticity. Oxford University Press, Oxford (1975)zbMATHGoogle Scholar
  24. 24.
    Katz, D., Tobolsky, A.V.: Rubber elasticity in a highly crosslinked epoxy system. Polymer (1963). Google Scholar
  25. 25.
    Schartel, B., Hull, T.R.: Development of fire-retarded materials—interpretation of cone calorimeter data. Fire Mater. (2007). Google Scholar
  26. 26.
    Schartel, B.: Phosphorus-based flame retardancy mechanisms—old hat or a starting point for future development? Materials (2010). Google Scholar
  27. 27.
    Perret, B., Schartel, B., Stöß, K., Ciesielski, M., Diederichs, J., Döring, M., Krämer, J., Altstädt, V.: A new halogen-free flame retardant based on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide for epoxy resins and their carbon fiber composites for the automotive and aviation industries. Macromol. Mater. Eng. (2011). Google Scholar
  28. 28.
    Weil, E.D.: Synergists, adjuvants and antagonists in flame-retardant systems. In: Grand, A.F., Wilkie, C.A. (eds.) Fire Retardancy of Polymeric Materials, pp. 115–145. Marcel Dekker Inc., New York (2000)Google Scholar
  29. 29.
    Petrella, R.V.: The assessment of full-scale fire hazards from cone calorimeter data. J. Fire Sci. (1994). Google Scholar
  30. 30.
    Wang, C.S., Lin, C.H.: Synthesis and properties of phosphorus-containing epoxy resins by novel method. J. Polym. Sci. A Pol. Chem. (1999).<3903::AID-POLA4>3.0.CO;2-XGoogle Scholar
  31. 31.
    Hussain, M., Varley, R.J., Mathus, M., Burchill, P., Simon, G.P.: Development and characterization of a fire retardant epoxy resin using an organo-phosphorus compound. J. Mater. Sci. Lett. (2003). Google Scholar
  32. 32.
    Lange, F.F.: The interaction of a crack front with a second-phase dispersion. Philos. Mag. (1970). Google Scholar
  33. 33.
    Jackson, G.V., Orton, M.L., Taylor, H.: Filled thermosets. In: Rothon, R.N. (ed.) Particulate-Filled Polymer Composites, pp. 425–488. Rapra Technology Limited, Shawbury (2003)Google Scholar
  34. 34.
    Lange, F.F., Radford, K.C.: Fracture energy of an epoxy composite system. J. Mater. Sci. (1971). Google Scholar

Copyright information

© Deutsches Zentrum für Luft- und Raumfahrt e.V. 2018

Authors and Affiliations

  • Thomas Neumeyer
    • 1
  • Anika Bauernfeind
    • 1
  • Verena Eigner
    • 1
  • Claudia Mueller
    • 1
  • Kerstin Pramberger
    • 1
  • Volker Altstaedt
    • 1
    Email author
  1. 1.Department of Polymer EngineeringUniversity of BayreuthBayreuthGermany

Personalised recommendations