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