United-Atom Molecular Dynamics Study of the Mechanical and Thermomechanical Properties of an Industrial Epoxy

Abstract

Epoxy resins are the most commonly used adhesives in industry due to their versatility, low cost, low toxicity, low shrinkage, high strength, resistance to moisture, and effective electrical resistance. These diverse properties can be tailored based on the chemical structure of the curing agent and the conditions of the curing process. Molecular simulations of epoxy resins have gained attention in recent years as a means to navigate the vast choice of chemical agents and conditions that will give the required properties of the resin. This work examines the statistical uncertainty in predicting thermodynamic and mechanical properties of an industrial epoxy resin using united atom molecular dynamics simulation. The results are compared with experimental measurements of the elastic modulus, Poisson’s ratio, and the glass transition temperature obtained at different temperatures and degrees of curing. The decreasing trend of the elastic modulus with increasing temperature is accurately captured by the simulated model, though the uncertainty in the calculated average is large. The glass transition temperature is expectedly overpredicted due to the high rates accessible to molecular simulations. We find that Poisson’s ratio is particularly sensitive to sample anisotropy as well as the method of evaluation, which explains the lack of consistent trends previously observed with molecular simulation at different degrees of crosslinking and temperatures.

An Accurate and Transferable Coarse-Graining Method for the Investigation of Microscopic Fracture Behaviors of Epoxy Thermosets

“…Standard combining rules are used, i.e., ε ij = (ε ii ε jj ) 1/2 and σ ij = (σ ii σ jj ) 1/2 . The initial values of LJ parameters (ε ij and σ ij ) in the CG model were extracted from OPLS-UA force field. − The reason is that OPLS-UA have already systematically calibrated the LJ parameters for various CH n groups that are also contained in the CG model, so parametrization referring to OPLS-UA (compared with OPLS-AA) is more efficient.…”

Molecular Dynamics Study of Cured ED-20 Epoxy Resin for Predicting the Glass Transition Temperature and Relationship with Structure Features

“…The determination of the glass transition temperature T g is usually based on the search for a break point in the temperature dependence of some physicochemical characteristic of a polymer. We used the dependence of the volume V of the simulation cell on the temperature T , a common technique; , however, we analyzed its natural logarithm and not the volume itself. We proceeded from the fact that the transition of EDR from a vitreous state to a viscoelastic state was accompanied by a change in thermal expansion coefficient β.…”

Full-Atomistic Optimized Potentials for Liquid Simulations and Polymer Consistent Force Field Models for Biocompatible Shape-Memory Poly(ε-caprolactone)

“…Classically optimized potentials for liquid simulations (OPLS) force field seems to be a suitable candidate, which is widely used for the simulation of proteins and DNA . OPLS was also successfully used for modeling the cross-linked structure of epoxy resin …”