Moisture diffusion in epoxy systems

✍ Scribed by M. R. Vanlandingham; R. F. Eduljee; J. W. Gillespie Jr.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 257 KB
• Volume: 71
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19990131)71:5<787::aid-app12>3.0.co;2-a

✦ Synopsis

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.