The automobile industry is incorporating more lightweight content in car designs to boost fuel-economy. New structural
adhesives are needed to mitigate the corrosion and thermal expansion issues associated with joining dissimilar lightweight
materials, but adhesive developers lack a fundamental understanding of the chemistry that occurs in the adhesive as the joint
ages. In this study, we developed structural adhesive molecular models and applied classical molecular dynamics simulations
and density functional theory calculations to gain molecular insights into the influence of water molecules on the properties
of epoxy-based adhesives (DGEBA + Jeffamine (JD230)). The simulations were complemented by experimental synthesis
and characterization. Our work underscores the impact of water molecules on the local structure of the epoxy network as
well as resulting mechanical properties. Water molecules were mainly coordinated with hydroxyls, primary amines and
secondary amines, but also weakly coordinated with ether linkages, which were found most probable to be labile. Simulated
stress–strain data indicates that increasing the water content deteriorates the mechanical properties. The Young’s modulus
decreased by ~ 30% when the water content increased to 3 wt%. This integration of molecular-level chemical insights with
mechanical property simulations of the hydrated epoxy system and experimental validation holds the promise to advance
lightweight joint technologies.
Published: October 14, 2023
Citation
Taufique M., M. Losada, S. Hamel, N. Goldman, M. DiTucci, L. Pagnotti, and D. Willis, et al. 2023.Molecular Dynamics Simulation of Hygroscopic Aging Effects in Epoxy Polymer.Integrating Materials and Manufacturing Innovation 12, no. 3:185–195.PNNL-SA-161079.doi:10.1007/s40192-023-00296-5