Abstract
It is increasingly appreciated that water is one of the most important factors in the durability behavior of coatings. The rate of water transportation and the degree of saturation of polymeric coatings depends on exposure history, exposure environment, and the nature of a coating. The focus here is on the time taken for transport of water and the variation it causes in thermal and mechanical properties, which have also been shown previously to have time-dependence that leads to discrepancies between different weathering regimes. This paper studied the effect of moisture on coatings’ mechanical properties and the effect of moisture and temperature on recovery of surface indentation. The reduction of mechanical properties and the increasing rate of surface defect relaxation can be explained in terms of plasticization by water. Recovery of surface defects is related to the appearance and diffusion activity of coatings during exposure. Thermogravimetric analysis showed that the content of moisture in the sample is determined by the ambient humidity, temperature, and the rate of change in these environmental parameters. Diffusion coefficients were determined from the weight change data and an activation energy was obtained via Arrhenius equation. Changes in yellowness, as an example, and signature of chemical degradation, indicated that the cycling period in accelerated weathering may affect the degradation via the amount and distribution of moisture in coatings. Diffusion of moisture is typically slow and limits the possibility of complete drying or saturation in an exposure cycle. Results from the cumulative effect of many cycles will be different depending on the conditions.
Similar content being viewed by others
References
Nguyen, T, Martin, J, Byrd, E, “Relating Laboratory and Outdoor Exposure of Coatings: IV. Mode and Mechanism for Hydrolytic Degradation of Acrylic-Melamine Coatings Exposed to Water Vapor in the Absence of UV Light.” J. Coat. Technol., 75 37–50 (2003)
Hollande, S, Laurent, JL, “Degradation Process of an Industrial Thermoplastic Elastomer Polyurethane-Coated Fabric in Artificial Weathering Conditions.” J. Appl. Polym. Sci., 73 2525–2534 (1999)
Real, LP, Gardette, JL, Rocha, AP, “Artificial Simulated and Natural Weathering of Poly(vinyl chloride) for Outdoor Applications: The Influence of Water in the Changes of Properties.” Polym. Degrad. Stab., 88 357–362 (2005)
Hinderliter, BR, Allahar, KN, Bierwagen, GP, Tallman, DE, Croll, SG, “Water Sorption and Diffusional Properties of a Cured Epoxy Resin Measured Using Alternating Ionic Liquids/Aqueous Electrolytes in Electrochemical Impedance Spectroscopy.” J. Coat. Technol. Res., 5 (4) 431–438 (2008)
Perera, DY, “Effect of Pigmentation on Organic Coating Characteristics.” Prog. Org. Coat., 50 247–262 (2004)
Colombini, D, Martinez-Vega, JJ, Merle, G, “Dynamic Mechanical Investigations of the Effects of Water Sorption and Physical Ageing on an Epoxy Resin System.” Polymer, 43 4479–4485 (2002)
Chin, J, Nguyen, T, Aoaudi, KJ, “Sorption and Transport Characteristics of Water, Salt Water and Concrete Pore Solutions in Polymer/Glass Fiber Composites.” Appl. Polym. Sci., 71 483–492 (1999)
Carfagna, C, Mastronardi, P, “Hygrothermal Aging of Epoxy Based Coatings.” J. Mater. Sci., 17 2239–2244 (1982)
Kim, HJ, Seo, DW, “Effect of Water Absorption Fatigue on Mechanical Properties of Sisal Textile-Reinforced Composites.” Int. J. Fatigue, 28 1307–1314 (2006)
Henderson, K, Hunt, R, Boisseau, J, Pattison, L, “The Importance of Water in the Weathering of Automotive Coatings.” JCT CoatingsTech, September 50–54 (2008)
Hardcastle, HK, Meeks, WL, “Consideration for Characterizing Moisture Effects in Coatings Weathering Studies.” JCT Res., 5 (2) 181–192 (2008)
Penon, MG, Picken, SJ, Wubbenhorst, M, Turnhout, JV, “Water Sorption in UV Degraded Clear and Pigmented Epoxy Coatings Assessed by Dielectric Sorption Analysis.” Polym. Degrad. Stab., 92 1247–1254 (2007)
National Oceanic and Atmospheric Administration (NOAA). http://www.ncdc.noaa.gov/oa/ncdc.html (2008)
Shi, XD, Fernando, BMD, Croll, SG, “Combined Physical Aging and Degradation of Two Crosslinked Coatings in Accelerated Weathering.” JCT Res., 5 (3) 299–309 (2008)
Spinks, GM, Brown, HR, Liu, Z, “Indentation Testing of Polystyrene Through the Glass Transition.” Polym. Test., 25 868–872 (2006)
Crank, J, The Mathematics of Diffusion, 2nd ed. Clarendon Press, New York (1975)
Croll, SG, Shi, XD, Fernando, BMD, “The Interplay of Physical Aging and Degradation During Weathering for Two Crosslinked Coatings.” Prog. Org. Coat., 61 136–144 (2008)
Vanlandingham, MR, Eduljee, RF, Gillespie, JW, Jr, “Moisture Diffusion in Epoxy Systems.” J. Appl. Polym. Sci., 71 787–798 (1999)
Ji, WG, Hu, JM, Zhang, JQ, Cao, CN, “Reducing the Water Absorption in Epoxy Coatings by Silane Monomer Incorporation.” Corros. Sci., 48 3731–3739 (2006)
http://hyperphysics.phy-astr.gsu.edu/HBASE/Kinetic/relhum.html, June 20 (2009)
van der Wel, GK, Adan, OCG, “Moisture in Organic Coatings—A Review.” Prog. Org. Coat., 37 1–14 (1999)
Hinderliter, BR, Allahar, KN, Bierwagen, GP, Tallman, DE, Croll, SG, “Thermal Cycling of Epoxy Coatings Using Room Temperature Ionic Liquids.” J. Electrochem. Soc., 155 (3) C93–C100 (2008)
Hashimoto, I, “Rate of Diffusion of Disperse Dye into Synthetic Fibers in Binary Mixed Solvents.” J. Text. Mach. Soc. Jpn., 32 (3) 162–166 (1979)
Cabanelas, JC, Prolongo, SG, Serrano, B, Bravo, J, Baselga, J, “Water Absorption in Polyaminosiloxane-Epoxy Thermosetting Polymers.” J. Mater. Process. Technol., 143 311–315 (2003)
Meissner, B, “Generalization of the WLF Equation and of the Free-Volume Concept for the Description of Transport Phenomena in the Glassy Region.” J. Polym. Sci.: Polym. Lett. Ed., 19 (3) 137–142 (2003)
Bao, LR, Yee, AF, “Effect of Temperature on Moisture Absorption in a Bismaleimide Resin and Its Carbon Fiber Composites.” Polymer, 43 3987–3997 (2002)
Soller, J, “Choosing the Appropriate Resin Epoxy vs. Vinylester vs. Polyester Resins.” http://www.sollercomposites.com/EpoxyResinChoice.html, June 20 (2009)
Philippe, L, Sammon, C, Lyon, SB, Yarwood, J, “An FTIR/ATR In Situ Study of Sorption and Transport in Corrosion Protective Organic Coatings Paper 2. The Effects of Temperature and Isotopic Dilution.” Prog. Org. Coat., 49 315–323 (2004)
Malshe, VC, Waghoo, G, “Weathering Characteristics of Epoxy-Ester Paints.” Prog. Org. Coat., 56 131–134 (2006)
Acknowledgment
This work was supported by funding from US Air Force Office of Scientific Research and Army Research Laboratory.
Author information
Authors and Affiliations
Corresponding author
Additional information
Presented at the 2009 CoatingsTech Conference, sponsored by NPCA/FSCT, April 28–29, 2009, in Indianapolis, IN.
Rights and permissions
About this article
Cite this article
Shi, X., Hinderliter, B.R. & Croll, S.G. Environmental and time dependence of moisture transportation in an epoxy coating and its significance for accelerated weathering. J Coat Technol Res 7, 419–430 (2010). https://doi.org/10.1007/s11998-009-9209-x
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11998-009-9209-x