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Sorption and Diffusion of Alkaline Solution in Organic Coatings at Ambient and Elevated Temperatures.


pdf icon Sorption and Diffusion of Alkaline Solution in Organic Coatings at Ambient and Elevated Temperatures. (261 K)
Nguyen, T.; Chin, J. W.; Aouadi, D. K.; Raghavan, D.

Polymeric Materials: Science and Engineering (PMSE) Fall Meeting. Volume 83. Proceedings. American Chemical Society (ACS) Division of Polymeric Materials: Science and Engineering. August 20-24, 2000, Washington, DC, American Chemical Society, Washington, DC, 319-320 pp, 2000.

Keywords:

coatings; temperature

Abstract:

Sorption and diffusion characteristics of an amine-cured epoxy (Tdg = 80 degrees C) and an isophthalic polyster (Tdg = 105 degrees C) coating in a pH 13.5 alkaline solution at 60 degrees C and 22 degrees C have been investigated. Free standing films having thicknesses between 250 micrometers and 300 micrometers were immeresed in the test solution, and mass change as a function of time was recorded gravimetrically. A diffusion coefficient was calculated using the sorption kinetics approach, and solubility was determined from data on the sorption at equilibrium and coating density. No reduction in mass was evidenced for both coatings exposed at ambient or at elevated temperature for the expoxy, even up to 400 h immersion. However, a mass loss due to base-catalyzed hydrolysis was observed after 100 h for the polyester immersed at 60 degrees C. Changing from ambient to 60 degrees C immersion resulted in a 14-fold jump in the diffusion coefficient of the epoxy, but produced a less than fourfold increase for the polyester coating. The diffusion of the alkaline solution in both coatings at ambient and elevated temperatures was Fickian.