Molecular Modeling of Physical Aging in Epoxy Polymers

Epoxy resins are often exposed to prolonged periods of sub-Tg temperatures which cause physical aging to occur. Because physical aging can compromise the performance of epoxies and their composites and because experimental techniques cannot provide all of the necessary physical insight that is needed to fully understand physical aging, efficient computational approaches to predict the effects of physical aging on thermo-mechanical properties are needed. In the current study a new method is developed to efficiently establish molecular models of epoxy resins that represent the corresponding molecular structure at specific aging times. Although this approach does not simulate the physical aging process directly, it is useful in establishing molecular models that resemble physicallyaged states of epoxies. Such models are useful for predicting the thermomechanical properties of aged epoxy resins to facilitate the design of durable engineering structures. For demonstration purposes, the developed method is applied to an EPON 862/DETDA epoxy system for three different crosslink densities.