Abstract
Atomic force microscopy (AFM) has been used to study the morphology and microstructure of an amine-cured epoxy before and after outdoor exposure. Measurements were made from samples prepared in an essentially CO2-free, H2O-free glove box and from samples prepared in ambient conditions. For those prepared in a CO2-free glove box, AFM imaging was conducted on (1) an unexposed air/coating surface, (2) an unexposed coating bulk, (3) an unexposed coating/substrate interface, and (4) a field exposed air/coating surface. For samples prepared in ambient conditions, only the unexposed air/coating surface was investigated. The same regions of the exposed samples were scanned periodically by the AFM to monitor changes in the surface morphology of the coating as UV exposure progressed. Small angle neutron scattering and Fourier transform infrared spectroscopy (FTIR) studies were performed to verify the microstructure and to follow chemical changes during outdoor exposure, respectively. The results have shown that amine blushing, which occurs only under ambient conditions, had a significant effect on the surface morphology and microstructure of the epoxy. The surface morphology of the samples prepared under CO2-free, dry conditions was generally smooth and homogeneous. However, the interface and the bulk samples clearly revealed a two-phase structure consisting of bright nodular domains and dark interstitial regions, indicating an inhomogeneous microstructure. Such heterogeneous structure of the bulk was in good agreement with results obtained by small angle neutron scattering of unexposed samples and by AFM phase imaging of the degraded sample surface. The relationship between submicrometer physical changes and molecular chemical degradation is discussed.
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References
Rabek, J.F., Polymer Photodegradation—Mechanisms and Experimental Methods, Chapman & Hall, New York, pp 269–278, 1995.
Bellinger, V., Bouchard, C., Claveirolle, P., and Verdu, J., “Photooxidation of Epoxy Resins Cured by Non-Aromatic Amines,” Polym. Photochemistry, 1, 69 (1981).
Bellinger, V. and Verdu, J., “Oxidative Skeleton Breaking in Epoxy-Amine Networks,” J. Appl. Polym. Sci., 30, 363 (1985).
Bellinger, V. and Verdu, J., “Structure-Photooxidative Stability Relationship of Amine-Crosslinked Epoxies,” Polym. Photochemistry, 5, 295–311 (1984).
Monney, L., Belali, R., Vebrel, J., Dubois, C., and Chambaudet, A., “Photochemical Degradation Study of an Epoxy Material by IR-ATR Spectroscopy,” Polym. Degrad. Stab., 62, 353–359 (1998).
Nguyen, T., Gu, X., VanLandingham, M.R., Ryntz, R., Nguyen, D., and Martin, J.W., “Nanoscale Characterization of Coatings Surface Degradation with Tapping Mode AFM,” Proc. Adhesion Society Meeting, Anderson, G.L. (Ed.), p. 505, 2003.
Nguyen, T., Gu, X., VanLandingham, M.R., Byrd, E., Martin, D., Ryntz, R., and Martin, J.W., “Degradation Modes of Polymeric Coatings Exposed to UV,” Proc. Coatings for Plastics Symposium, Troy, MI, July, 2004.
Morgan, R.J. and O’Neal, J.E., “The Durability of Epoxies,” Polym.-Plast. Technol. Eng., 10, 49–116 (1978).
Kenyon, A.S. and Nielsen, L.E., J. Macromol. Sci., Chem., A3 (2), 275 (1969).
Erath, E.H. and Robinson, M., J. Polym. Sci., Part C, 3 65 (1963).
Cuthrell, R.E., “Epoxy Polymers. II. Macrostructure,” J. Appl. Polym. Sci., 12, 1263 (1968).
Karyakina, M.V., Mogilevich, M.M., Maiorova, N.V., and Udalova, A.V., “Structure Formation Processes at Stages Preceding Formation of Network Polymers,” Vysokomol. Soedin., A17, 466–470 (1975).
Dusek, K., “Are Cured Thermoset Resins Inhomogeneous?,” Angewandte Makromol. Chem., 240, 1–15 (1996).
Dusek, K., Plestil, J., Lednicky, F., and Lunak, S., “Are Cured Epoxy-Resins Inhomogeneous,” Polymer, 19, 393–397 (1978).
Oberlin, A., Ayache, J., Oberlin, M., and Guigon, M., “High-Resolution Dark-Field Imaging in Epoxy and Polyimide Systems,” J. Polym. Sci., Polym. Phys., Ed. 20, 579–591 (1982).
Duchet, J. and Pascault, J.P., “Do Epoxy-Amine Networks Become Inhomogeneous at the Nanometric Scale?,” J. Polym. Sci. Polym. Phys., Ed. 41, 2422–2432 (2003).
Thomas, H.R. and Omalley, J.J., “Surface Studies on Multicomponent Polymer Systems by X-ray Photoelectron-Spectroscopy-Polystyrene-Poly(ethylene oxide) Diblock Copolymers,” Macromolecules, 12, 323–329 (1979).
Lee, W.K., Cho, W.J., Ha, C.S., Takahara, A., and Kajiyama, T. “Surface Enrichment of the Solution-Cast Poly (methyl methacrylate) Poly (vinyl acetate) Blends,” Polymer, 36, 1229–1234 (1995).
Ebbens, S.J. and Badyal, J.P.S., “Surface Enrichment of Fluorochemical-Doped Polypropylene Films,” Langmuir, 17, 4050–4055 (2001).
Chen, X., McGurk, S.L., Davies, M.C., Roberts, C.J., Shakesheff, K.M., Tendler, S.J., and Williams, P.M., “Chemical and Morphological Analysis of Surface Enrichment in a Biodegradable Polymer Blend by Phase-Detection Imaging Atomic Force Microscopy,” Macromolecules, 31, 2278–2283 (1998).
Cleveland, J.P., Anczykowski, B., Schmid, A.E., and Elings, V.B., “Energy Dissipation in Tapping-Mode Atomic Force Microscopy,” Appl. Phys. Lett., 72, 2613–2615 (1998).
Magonov, S.N. and Reneker, D.H., “Characterization of Polymer Surfaces with Atomic Force Microscopy,” Annu. Rev. Mater. Sci., 27, 175–222 (1997).
Magonov, S.N., Elings, V., Whangbo, M.H., “Phase Imaging and Stiffness in Tapping-Mode Atomic Force Microscopy,” Surf. Sci., 375, L385-L391 (1997).
Bar, G., Thomann, Y., and Whangbo, M.H., “Characterization of Morphologies and Nanostructures of Blends of Poly(styrene) Block-Poly(ethane-co-but-1-ene)-Block-Poly(styrene) with Isotactic and Atactic Polypropylenes by Tapping-Mode Atomic Force Microscopy,” Langmuir, 14, 1219–1226 (1998).
Raghavan, D., Gu, X., Nguyen, T., VanLandingham, M.R., and Karim, A., “Mapping Polymer Heterogeneity Using Atomic Force Microscopy Phase Imaging and Nanoscale Indentation,” Macromolecules 33, 2573–2583 (2000).
Raghavan, D., Gu, X., Nguyen, T. and Vanlandingham, M.R., “Characterization of Chemical Heteogeneity in Polymer System Using Hydrolysis and Tapping-Mode Atomic Force Microscopy,” J. Polym. Sci., Polym. Phys., 39, 1460–1470 (2001).
Gu, X., Raghavan, D., Nguyen, T., and VanLandingham, M.R., “Characterization of Polyester Degradation Using Tapping Mode Atomic Force Microscopy: Exposure to Alkaline Solution at Room Temperature,” Polym. Degrad. Stab., 74, 139–149 (2001).
VanLandingham, M.R., Eduljee, R.F., and Gillespie, J.W., “Relationship between Stoichiometry, Microstructure, and Properties of Amine-Cured Epoxies,” J. Appl. Polym. Sci., 71, 699 (1999).
Nguyen, T., Martin, J.W., Byrd, W.E., and Embree, N., “Relating Laboratory and Outdoor Exposures of Coatings: II. Effects of Relative Humidity on Photodegradation of Acrylic Melamine,” Journal of Coatings Technology, 74, No. 932, 31 (2002).
Burton, B.L., “Amine-Blushing Problems? No Sweat!,” Proc. Epoxy Resin Formulators’ Meeting of the Society of the Plastics Industry, July, 2001.
Pierce, P.E., and Schoff, C.K., “Coating Film Defects,” Federation Series on Coatings Technology, Blue Bell, PA, pp. 7–24, 1998.
Sung, L., Karim, A., Douglas, J.F., and Han, C.C., “Dimensional Crossover in the Phase Separation Kinetics of Thin Polymer Blend Films,” Phys. Rev. Lett., 76, 4368–4371 (1996).
Koch, S.W., Desai, R.C., and Abraham, F.F., “Dynamics of Phase-Separation In Two-Dimensional Fluids—Spinodal Decomposition,” Phys. Rev. A: At., Mol., Opt. Phys., 27, 2152–2167 (1983).
Gu, X., Raghavan, D. Ho., D.L., Sung, L., VanLandingham, M.R., and Nguyen, T., “Nanocharacterization of Surface and Interface of Different Epoxy Networks,” Materials Research Society Symposium, 710, DD10.9, 2002.
Gu, X., Martin, D., Martin, W.J., and Nguyen, T., “Surface, Interface, and Bulk Microstructure of Amine-Cured Epoxies—An Intensive AFM Study,” Proc. Adhesion Society Meeting, M. Chaudhury (Ed.), p. 507, 2004.
Nguyen, T., Martin, J.W., Byrd, W.E., and Embree, N., “Relating Laboratory and Outdoor Exposures of Coatings: IV. Mode and Mechanism of Hydrolysis of Acrylic-Melamine Coatings,” Journal of Coatings Technology, 75, No. 941, 37 (2003).
Gu, X., Nguyen, T., Nguyen, D., and VanLandingham, M.R., “Surface and Interface Properties of PVDF/Acrylic Copolymer Blends,” Proc. Adhesion Society Meeting, Orlando, FL, February 2002.
Zhang, G., Pitt, W.G., Goates, S.R., and Owen, N.L., “Studies on Oxidative Photodegradation of Epoxy Resins by IR-ATR Spectroscopy,” J. Appl. Polym. Sci., 54, 419–427 (1994).
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Gu, X., Nguyen, T., Oudina, M. et al. Microstructure and morphology of amine-cured epoxy coatings before and after outdoor exposures—An AFM study. J Coat. Technol. Res. 2, 547–556 (2005). https://doi.org/10.1007/s11998-005-0014-x
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DOI: https://doi.org/10.1007/s11998-005-0014-x