The effect of water sorption, high temperature aging, and cooling rate on the calorimetric signature of the aging of an epoxy glass

Stephan Comeau, Brandon McReynolds, Taylor Le
John D. McCoy, Jamie M. Kropka 2
American Physical Society March Meeting 2020
New Mexico Institute of Mining and Technology
2) Sandia National Laboratories

The cure of DGEBA with diethanolamine results in an epoxy that is susceptible to complex aging signatures. Aging at room temperature (about 50°C below Tg) and ambient humidity results in three distinct features: a pre-Tg peak starting 30°C below Tg, a broad post-Tg Shoulder from Tg (75°C) to 175°C, and a decrease in Cp between 175°C and 200°C (chemical aging). Unlike the other features the high-T decrease in Cp persists after the first heat. Extended isothermal holds at 200°C remove the high-T decrease in Cp and slightly increase the Tg (indicating additional cure). Water soaked samples and samples stored in sub ambient contiditons, show an evolving pre-Tg peak and an evolving post Tg-shoulder. The pre-Tg peak also occurs in Samples rapidly cooled (10°C/min) from above Tg and then aged.