A Molecular Simulation Approach to Bond Reorganization in Epoxy Resins: From Curing to Deformation and Fracture

Abstract

We model bond formation and dissociation processes in thermosetting polymer networks from molecular dynamics simulations. For this, a coarsened molecular mechanics model is derived from quantum calculations to provide effective interaction potentials that enable million-atoms scale simulations. The importance of bond (re)organization is demonstrated for (i) simulating epoxy resin formationfor which our approach leads to realistic network models which can now account for degrees of curing up to 98%. Moreover, (ii) we elucidate the competition of bond dissociation and bond reformation during plastic deformation and fracture. On this basis, we rationalize the molecular mechanisms that account for the irreversible nature of damaging epoxy polymers by mechanical load.

Accurate predictions of thermoset resin glass transition temperatures from all-atom molecular dynamics simulation

“…Numerous studies have investigated MD methods for predicting the T g of thermoset resins. [1][2][3][4]8,9,13,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Some of these studies 1,3,22,23,29,38 employ a cooling rate correction factor to correct the predicted values of T g to match those measured under laboratory conditions with much slower cooling rates. Specifically, the well-established Williams-Landel-Ferry equation 39,40 has been used to reduce the apparent predicted T g by about 3 K per decade of cooling rate (about 30 K for most MD simulations).…”

Block chemistry for accurate modeling of epoxy resins

“…26,38,55 It has been recognized that the energetic barriers of the individual reactions are very prohibitive for time scales observable with MD simulations and anyways would need to be artificially smoothed out or boosted to allow any reaction to take place. 18,38,56 Scheme 5 Reaction site templates for the first (left) and the second (right) curing reaction. Situation before (top) and after (bottom) the reaction are presented.…”

A study of the mechanical properties of the NEPE binders by molecular dynamic simulations and experiments

“…Recently, MD simulation has been used to construct crosslinked structural models of polymers. 32,33 The crosslinking reaction between a prepolymer and curing agent containing isocyanate group follows the principle of addition polymerization. The curing reaction mechanism of the binders is presented in Fig.…”