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Moisture diffusion in epoxy systems
Author(s) -
Vanlandingham M. R.,
Eduljee R. F.,
Gillespie J. W.
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19990131)71:5<787::aid-app12>3.0.co;2-a
Subject(s) - materials science , epoxy , stoichiometry , moisture , relative humidity , swelling , saturation (graph theory) , diffusion , composite material , glass transition , fick's laws of diffusion , water content , polymer chemistry , thermodynamics , chemistry , polymer , physics , mathematics , geotechnical engineering , combinatorics , engineering
The moisture diffusion process of an epoxy system is studied as a function of epoxy‐amine stoichiometry and the resulting microstructure. Differences in diffusion behavior are related to the relative importance of diffusion through the low‐density and high‐density microstructural phases for different stoichiometries. Also, changes in saturation level with stoichiometry are explained by competing effects of free volume versus the content of the low‐density phase. Increasing the humidity level causes a corresponding increase in saturation level, while increasing the temperature causes more pronounced non‐Fickian behavior. The effects of absorbed moisture on the thermomechanical properties of the epoxies are also investigated. Reductions in the glass transition temperature, T g , and moisture‐induced swelling strains are measured after exposure of samples to the three conditioning environments. Moisture‐induced swelling strains increase with increasing moisture content. The reductions in T g range from 5 to 20°C and are generally larger for amine‐rich samples than for epoxy‐rich and stoichiometric samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 787–798, 1999