Wettability under Imposed Flow as a Function of the Baking Temperatures of a DGEBA Epoxy Resin Used in the Crude Oil Industry Cristina M. Quintella,* ,† Leila A. Friedrich, † Ana Paula S. Musse, † A ˆ ngelo M. V. Lima, † Marcelo A. Mace ˆdo, ‡ Ramires M. Silva, ‡ Iuri M. Pepe, § Eduardo B. Silva, † Heitor M. Quintella, † and Luiz Carlos S. Soares, Jr. ‡ Inst. Quı ´mica, UniVersidade Federal da Bahia, Campus de Ondina, 40170-290, SalVador, BA, Brazil, Dep. Fı ´sica, UniVersidade Federal de Sergipe, CEP: 40.100-000, Sa ˜ o Cristo ´ Va ˜ o, SE, Brazil, and Inst. de Fı ´sica, UniVersidade Federal da Bahia, Campus de Ondina, SalVador, BA, Brazil ReceiVed NoVember 4, 2006 The baking temperature (Tb) of an epoxy resin was optimized in order to decrease the dynamic interfacial tension, identifying the lowest wettability conditions for liquids flowing at a high rate. The dependence of dynamic interfacial tension on Tb was evaluated for the diglycidyl ether of bisphenol A. This resin was used to coat a sucking rod at the oil field of Bacia de Sergipe/Alagoas, Brazil in order to reduce blockage occurrences, maintenance stops, and the pumping capacity required. The samples were baked for 24 h between 100 and 180 °C. Their color and absorption spectra showed progressive dependence of Tb, indicating a migration from polymerization, through polymer network degradation, until carbonization. Spectrofluorimetry showed an initial increase in the energy gap between absorption and emission followed by a decrease that was attributed to changes of the chemical environment isotropy. Fourier transform infrared spectroscopy showed that the maximum polymerization occurred at 140 °C. Dynamic interfacial tension was evaluated by fluorescence depolarization of induced flowing liquids, using polarized laser-induced fluorescence within induced liquid flows and was clearly dependent on Tb. The lowest dynamic wettability was at 120 °C, just before full polymerization, which was attributed to two competing effects as Tb increased: polymerization and progressive yielding of compounds from the epoxy degradation. This points to the need to review the standard application procedures of these resins. 1. Introduction A recent trend in crude oil transport involves the use of ducts made of plastics, amorphous polymers, and fiber-reinforced plastic polymers. They may be used either as coatings or linings for metallic ducts or as massive ducts. Although they cannot stand high temperatures and their low mechanical resistance is a concern, they have the advantage of impeding the formation of paraffin deposits 1-4 and a much lower corrosion rate than unlined metallic ducts. They are already being used 5 to recuperate condemned metallic ducts by insertion of a plastic layer as inner lining, thus reducing the costs of welding and equipment maintenance or replacement. Nowadays, most of the ducts for production and transport are metallic. Nevertheless, in the middle to long term, most of the production tubing and tools, transportation ducts, and pipelines will need to be customized to the operational condi- tions and to the types of fluids they transport in order to decrease financial losses and to preserve the environment. These tailor- made ducts must reduce the chemical affinity with the fluids, that is, decrease the wetting efficiency that leads to degradation like corrosion and formation of asphaltenic and paraffinic deposits. At present, epoxy resins are among the most used materials for linings and coatings in the crude oil industry due to their availably in the international market, low price, and application versatility. They may also be used with fibers 6 or as composites with other materials. Intrinsic luminescence of the epoxy resins has been studied before and related to cure degree. At room temperature, this is due mainly to 7 fluorescence of the bisphenol from base resin and from the hardener, the aliphatic amines being well-known quenchers of the aromatic hydrocarbons. As a result of the cure process, the aliphatic amines are converted from primary to tertiary amines, increasing the quenching effects. On the basis of these, several methods were proposed to evaluate the cure degree and the oxidation process of the epoxy resin. 7-9 * Corresponding author. Tel. 55-71-88677876. Fax. 55-71-32355166. E-mail: cristina@ufba.br. † Inst. Quı ´mica, Universidade Federal da Bahia. ‡ Universidade Federal de Sergipe. § Inst. de Fı ´sica, Universidade Federal da Bahia. (1) Slack, M. Mater. Perform. 1992, 31, 49. (2) Attou, A.; Benamar, A.; Inglebert, G. Mec. Indust. Mater. 1997, 50, 109. (3) Quintella, C. M.; Musse, A. P. S. M.; Castro, T. P. O.; Watanabe, Y. N. Energy Fuels 2006, 20, 620. (4) Quintella, C. M.; Lima, A. M. V.; Silva, E. B. J. Phys. Chem. B 2006, 110, 7587. (5) Refinarias Petrobras, Lubnor: Lubrificantes e Derivados de Petroleo do Nordeste. www2.petrobras.com (accessed May 2007). (6) Holmes, G. A.; Feresenbet, E.; Raghavan, D. Compos. Interfaces 2003, 10, 515. (7) Gallot-lavalle, O.; Teyssedrea, G.; Laurenta, C.; Rowe, S. Polymer 2005, 46, 2722. (8) Rigail-Cedeno, A.; Sung, C. S. P. Polymer 2005, 46, 9378. (9) Younes, M.; Wartewig, S.; Lellinger, D.; Strechmel, B.; Strechmel, V. Polymer 1994, 35, 5269. 2311 Energy & Fuels 2007, 21, 2311-2316 10.1021/ef060551w CCC: $37.00 © 2007 American Chemical Society Published on Web 06/05/2007