Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC.

Shuang Yan,Harald Zeizinger,Wolfgang Verestek,Siegfried Schmauder

doi:10.3390/polym13183085

Abstract

The curing behavior of a thermosetting material that influences the properties of the material is a key issue for predicting the changes in material properties during processing. An empirical equation can describe the reaction kinetics of the curing behavior of an investigated material, which is usually estimated using experimental methods. In this study, the curing process of an epoxy resin, the polymer matrix in an epoxy molding compound, is computed concerning thermal influence using molecular dynamics. Furthermore, the accelerated reaction kinetics, which are influenced by an increased reaction cutoff distance, are investigated. As a result, the simulated crosslink density with various cutoff distances increases to plateau at a crosslink density of approx. 90% for the investigated temperatures during curing time. The reaction kinetics are derived according to the numerical results and compared with the results using experimental methods (dielectric analysis and differential scanning calorimetry), whereby the comparison shows a good agreement between experiment and simulation.

Highlights

Thermoset materials are widely used in the industrial sector because of their excellent mechanical properties at high temperatures and good chemical resistance
The reaction kinetics are derived according to the numerical results and compared with the results using experimental methods, whereby the comparison shows a good agreement between experiment and simulation
The influence of rising environment temperature on the crosslink density is not significantly identified regarding numerical results computed with a cutoff distance of ≥ 1.7 Å

Summary

Introduction

Thermoset materials are widely used in the industrial sector because of their excellent mechanical properties at high temperatures and good chemical resistance. The non-cured thermosetting resin contains many monomers, which crosslink from a specific temperature and build three-dimensional macromolecules during processing. Since it causes changes in dynamical viscosity and temperature in the material, it is essential to know how the cure behavior changes during processing, e.g., the injection molding process. Using the measurement technology to monitor curing involves a high cost and effort and, in terms of the manufacturing process, the sensors cannot be adopted at every position where the curing state in the material needs to be measured. The molecular changes in morphological structure caused by the curing, which influence the material properties, are more predicted and analyzed with the help of molecular dynamics (MD) simulation

Methods

Results

Conclusion