Infrared and Ultraviolet–Visible Spectroscopy Study of the Degradation of Polyester and Polyester/Ethylene Methyl Acrylate Copolymer Blend Coatings on Steel Vanessa de Freitas Cunha Lins, 1 Fla ´via Medina Cury, 1 Roberto Moreira 2 1 Corrosion and Surface Engineering Laboratory, Chemical Engineering Department, Federal University of Minas Gerais, Rua Espirito Santo 35, 6th Floor, Belo Horizonte, Brazil 30160-030 2 Department of Physics, Federal University of Minas Gerais, Presidente Antonio Carlos Avenue 6627, Belo Horizonte, Brazil 31270-010 Received 22 June 2006; accepted 4 December 2007 DOI 10.1002/app.28231 Published online 2 May 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Thermally sprayed polymer coatings have been used as protection against corrosion and wear. The aim of this study was to produce coated steel with a blend film with low-velocity combustion thermal spraying and a fusion technique and to evaluate its chemical degradation with infra- red and ultraviolet–visible spectroscopy. The substrate used was carbon steel coated with recycled poly(ethylene terephtha- late) (PET), an ethylene/methacrylic acid copolymer (EMAA), or PET–EMAA blends. The degradation of the material was evaluated with an ultraviolet condensation–weathering test and a salt-spray test. Measurements of hardness and adhesion were carried out. The tribological properties of the polymeric films were evaluated with a pin-on-disc test. Ó 2008 Wiley Peri- odicals, Inc. J Appl Polym Sci 109: 2103–2112, 2008 Key words: blends; coatings; FTIR; polyesters; recycling INTRODUCTION Thermally sprayed polymer coatings have been used as protection against corrosion and wear. 1,2 Several polymers have been thermally sprayed, including polyethylene, the copolymer of ethylene and metha- crylic acid, poly(methyl methacrylate), polyamide, and polyesters. 1,3,4 In this study, recycled poly(ethylene terephthalate) (PET) and an ethylene/methacrylic acid copolymer (EMAA) were used as surface coatings on carbon steel with the purpose of obtaining a coating with corrosion resistance. PET was chosen because its production is growing worldwide because of its utilization in soft drink bottles. 5 Several million tons of PET postconsumer plastic waste reaches the environment, and of this, only 7% is recycled to produce low-grade plastic product. 6 EMAA was used because of its availability and known characteristics. EMAA has been used in coat- ings because of its versatility in different environ- ments. 7 Its adhesive properties, already known, makes it useful for application on surfaces that require adhesion, such as in painting, skin protec- tion, medical application, 8 and coated metal. The mechanism of interfacial interaction between EMAA and carbon steel consists of the interaction between the hydrogen of the hydroxyls of Fe(OH) 2 on the steel surface and the oxygen of the carboxyl. 3 The carboxyl disrupts the linearity of the polyethylene backbone, interferes as well with chain alignment, and reduces the total crystallinity, as in the case of other ethylene copolymers. 9 The acid functionality allows the polymers to form strong bonds to polar substrates. The useful life of polymeric coatings depends on the rate and type of structural change that occurs during the time. If the polymer presents a visible change in its surface after the aging process, the ma- terial fails, even if there was no significant change in the material properties. 10 Degradation by environ- mental exposure is caused by radiation, temperature, humidity, and pollutants. Photon energy produced by ultraviolet light is a powerful source and is highly effective in breaking chemical bonds such as CÀÀH and OÀÀH. 11 Photodegradation may generate chemical groups such as carbonyl, carboxyl, and hydroperoxides. 12–14 PET degradation has been extensively studied, and many mechanisms have been proposed to account for its various types of degradation, 15–21 but not many articles have been published about the Correspondence to: V. de Freitas Cunha Lins (vanessa.lins@ terra.com.br). Contract grant sponsor: Conselho Nacional de Desenvol- vimento Cientifico e Tecnolo ´ gico. Contract grant sponsor: Fundac ¸a ˜o de Amparo a ` Pesquisa do Estado de Minas Gerais. Journal of Applied Polymer Science, Vol. 109, 2103–2112 (2008) V V C 2008 Wiley Periodicals, Inc.