Equilibrium moisture content of a crosslinked epoxy network via molecular dynamics simulations

Abstract

Abstract. This study presents molecular dynamics (MD) simulation methods for determining the solubility limit of water in a crosslinked epoxy network. Procedures are first presented for dynamically crosslinking an epoxy network consisting of diglycidyl ether bisphenol A (DGEBA) and isophorone diamine (IPD). Water molecules are then introduced into the crosslinked DGEBA-IPD structure. The excess chemical potential for the absorbed water was determined through combining thermodynamic integration and Widom's test particle insertion methods. The limiting moisture uptake of the epoxy structure was determined through comparing the reduced chemical potential of the water held within the epoxy to that of pure water. The DGEBA-IPD epoxy system was found to have a moisture solubility of 3.50-3.75 wt.% when immersed in water at 300 K.

Reduced interfacial adhesion in glass fibre-epoxy composites due to water absorption via molecular dynamics simulations

“…256 reactive DGEBA and 128 reactive IPD molecules were packed above the existing sized glass fibre cell to a thickness of 100 Å, chosen to give approximately the correct density found in our previous work [10]. The packing tolerance was specified as 2 Å.…”

“…Initially, 50 ps of NVT dynamics were run as before. The relaxed epoxy structure was then dynamically crosslinked under an NVT ensemble, following our previous work [10]. The DGEBA-IPD system obtained a 91.5% crosslink density.…”

“…Noble water has Coulombic interactions deactivated, Lennard-Jones interactions of the hydrogen atoms switched off, and oxygen atoms scaled to 80% of their original size. This scaling leads to a much higher success rate of particle insertions, greatly decreasing computational time [10]. In the current work, Grand Canonical Monte Carlo (GCMC) exchanges of noble water molecules were performed.…”

“…Recently, Molecular Dynamics (MD) simulation has proven to be a powerful tool for investigating molecular level interactions in polymeric systems [10][11][12]. Clancy and Mattice investigated the interface between polymer-polymer systems using MD methods [13].…”

On the Nature of Epoxy Resin Post-Curing

“…We know of no reports of simulation of epoxy network formation by amine addition followed by etherification and dehydrative degradation. There have been reports of atomistic simulations of crosslinking which include specific bond formation to create secondary and tertiary amines [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], bond formation among other specific molecular group pairs [32][33][34][35][36][37][38][39][40][41], link formation among coarse-grain entities [42], special bond reactions [43], and simulated multiple selected reactions based on known kinetic rates [44,45].…”