Thermally Induced Changes in the Chemical and Mechanical Properties of Epoxy Foam

Abstract

The influence of thermal treatment on the chemistry, physical, and mechanical properties of epoxy foam was evaluated. The foam was subjected to repeated thermal cycles (25—95°C), encompassing the temperature regime in which the forward and the retro Diels—Alder reaction occurs. Changes in the chemistry of the foam were evaluated using in situ FTIR spectroscopy during thermal exposure. In addition, the structural siloxane units within the epoxy foam were identified and evaluated using FTIR analysis. Thermal analysis was used to evaluate expansion, degradation, and mass loss during thermal exposure. Finally, the physical and mechanical properties were evaluated to determine how thermal cycling influences the density and modulus of the epoxy foam. Thermal exposure below the temperature required for the breakage of conjugated double bonds via Diels—Alder mechanism increases thermal expansion influencing the structural integrity and packing of siloxane chains. The data indicates that the chemical changes and the thermal expansion of the foam are irreversible. The combination of thermal expansion and the change in chemistry for the system strongly diminished the structural rigidity of the foam lowering the density and modulus of the material.

Keywords

Diels—Alder epoxy foam FTIR modulus density.

Get full access to this article

View all access options for this article.

References

Hatchett, D.W. , Kinyanjui, J.M. and Sapochak, L. FTIR Analysis of Chemical Gradients in Thermally Processed Molded Polyurethane Foam, J. Cell. Plast., 2007: 43: 183-196.

Hatchett, D.W. , Kodippili, G. , Kinyanjui , J.M. , Benincasa, F. and Sapochak, L. FTIR Analysis of Thermally Processed PU Foam , Polym. Degrad. Stab., 2005: 87: 555-561.

McElhanon, J.R. , Russick, E.M. , Wheeler, D.R. , Loy , D.A. and Aubert, J.H. Removable Foams Based on an Epoxy Resin Incorporating Reversible Diels-Alder Adducts , J. Appl. Polym. Sci., 2002: 85: 1496-1502.

Russick, E.M. and Rand, P.B. Development and Characterization of a New Epoxy Foam Encapusulant as Ablefoam Replacement, Sandia National Laboratory Report, 98-2538, Sandia National Laboratory, Albuquerque, NM, 1998.

Loy D.A. , Wheeler, D.R. , Russick, E.M. , McElhannon, J.R. and Saunders, R.S. Method of Making Thermally Removable Epoxies, US Patent 6337384, January 8, 2002.

Small, J.H. , Loy, D.A. , Wheeler, D.R. , McElhannon, J.R. , Saunders, R.S. and Randall, S. Method of Making Thermally Removable Polymeric Encapsulants, US Patent 6271335, August 7, 2001.

Kent, J.A. (ed.) (2003). Riegel’s Handbook of Industrial Chemistry, New York , Kluwer Academics/Plenum Publishers .

Sbirrazouli, N. , Mititeli-Mija, A. , Vincent , L. and Alzina, C. Isoconversional Kinetic Analysis of Stochiometric and Off-stochiometric Epoxy-amine Cures , Thermochim. Acta , 2006: 447: 167-177.

Lin, S.-T. and Huang, S.K. Thermal Degradation Study of Siloxane-DGEBA Epoxy Copolymers, Eur. Polym. J., 1997: 33: 365-373.

10.

Hobbs, M.L. Modeling Epoxy Foams Exposed to Fire Like-heat Fluxes, Polym. Degrad. Stabil., 2005: 89: 353-372.

11.

Dvornic, P.R. , Perpall, H.J. , Uden, P.C. and Lenz, R.W. Exactly Alternating Silarylene-siloxane Polymers. VII. Thermal Stability and Degradation Behavior of P-silphenylene-siloxane Polymers with Methyl, Vinyl, Hydrido, and/or Fluoralky Side Groups, J. Polym. Sci. Part A Polym. Chem., 1989: 27: 3503-3514.

12.

Chang, T.C. , Wu, K.H. , Liao, C.L. , Lin , S.T. and Wang, G.P. Thermo-oxidative Degradation of Siloxane-Containing Polyimide and Unmodified Polyimide, Poly.r Degrad. Stabil. , 1998: 62: 299-305.

13.

Aubert, J.H. , Tallant, D.R. , Sawyer, P.S. and Garcia, M.J. ( 2004). Synthesis and Formulation of a Removable Conformal Coating Using Diels-Alder Thermally-Reversible Adducts , In: ACS Fall National Meeting, Poly, PMSE and FSCT Preprints, Philadelphia, PA.

14.

Pavia, D.L. , Lampman, G.M. and Kriz, G.S. ( 1979). Introduction to Spectroscopy: A Guide for Students of Organic Chemistry, Orlando, Saunders College Publishing.

15.

Silvestein, R.M. and Webster, F.X. ( 1998). Spectrometric Identification of Organic Compounds , New York, John Wiley & Sons .

16.

Laita, H. , Boufi, S. and Gandini, A. The Application of the Diels-Alder Reaction to Polymers Bearing Furan Moieties. 1. Reactions with Maleimides, Eur. Polym. J., 1997: 33: 1203-1211.

17.

Imai, Y. , Itoh, H. , Naka, K. and Chujo, Y. Thermally Reversible IPN Organic-Inorganic Polymer Hybrids Utilizing the Diels-Alder Reaction, Macromolecules, 2000: 33: 4343-4346.

18.

Aubert, J.H. Thermally Removable Epoxy Adhesives Incorporating Thermally Reversible Diels-Alder Adducts, J. Adhes., 2003: 79: 609-616.

19.

Adachi K. , Achimuthu A.K. and Chujo Y. Synthesis of Organic-Inorganic Polymer Hybrids Controlled by Diels-Alder Reaction , Macromolecules, 2004: 37: 9793-9797.

20.

Hatakayema, T. , Matsumoto, Y. , Asano , Y. and Hatakayema, H. Glass Transition of Rigid Polyurethane Foams Derived from Sodium Lignosulfonate Mixed with Diethylene, Triethylene and Polyethylene Glycols, Thermochim. Acta, 2004 : 416: 29-33.

21.

Gibson, L.J. and Ashby, M.F. ( 1997). Cellular Solids: Structure and Properties, Cambridge, Cambridge University Press.

22.

Hirose, S. , Hatakeyama, T. and Hatakeyama, H. Glass Transition and Thermal Decomposition of Epoxy resins from the Carboxylic Acid System Consisting of Ester-Carboxylic Acid Derivatives of Alcoholysis Lignin and Ethylene Glycol with various Dicarboxylic Acids, Thermochim. Acta, 2005: 431: 76-80.

23.

Wang, H. and Siow K.S. Measurement of Tg in Epoxy Resins by DSC-Effects of Residual Stress , Polym. Eng. Sci., 1999: 39: 422-429.

24.

Wu, C.S. Influence of Post-Curing and Temperature Effects on Bulk Density, Glass Transition and Stress Strain Behaviour of Imidazole-Cured Epoxy Network, J. Mater. Sci., 1992: 27: 2952-2959.

25.

Jackovich, D. , O’Toole, B. , Hawkins , M.C. and Sapochak, L. Temperature and Mold Size Effects on Physical and Mechanical Properties of a Polyurethane Foam, J. Cell. Plast., 2005: 41: 153-168.

26.

Hawkins, M.C. , O’Toole, B. and Jackovich, D. Cell Morphology and Mechanical Properties of Rigid Polyurethane Foam, J. Cell. Plast., 2005: 41: 267-285.