A Molecular Dynamics Study of Epoxy-Based Networks: Cross-Linking Procedure and Prediction of Molecular and Material Properties

TLDR

Molecular modeling of thermosetting polymers, particularly atomistic models, has been explored with various approaches to building highly cross‑linked networks. The study proposes a multistep relaxation procedure to relax molecular topology during cross‑linking. The procedure is applied to an EPON‑862/DETDA epoxy thermoset, modeling its cross‑linking and relaxation. Calculated properties—density, glass‑transition temperature, thermal‑expansion coefficient, and volume shrinkage—agree with experiment, and simulations reveal molecular‑weight distribution and gel‑point onset during network formation.

Abstract

Molecular modeling of thermosetting polymers has been presented with special emphasis on building atomistic models. Different approaches to build highly cross-linked polymer networks are discussed. A multistep relaxation procedure for relaxing the molecular topology during cross-linking is proposed. This methodology is then applied to an epoxy-based thermoset (EPON-862/DETDA). Several materials properties such as density, glass transition temperature, thermal expansion coefficient, and volume shrinkage during curing are calculated and found to be in good agreement with experimental results. Along with the material's properties, the simulations also highlight the distribution of molecular weight buildup and inception of gel point during the network formation.