Molecular dynamic simulation on the interaction and compatibility between ammonium dinitramide and typical fluoropolymers in solid propellants

In order to determine the interaction and compatibility of ADN with the most commonly used fluorine-containing binder in solid propellant, molecular dynamics (MD) simulations with Dreiding force filed were performed to study the interaction and compatibility of ADN with hydroxyl-terminated liquid fluorrubber 26 (F26), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) from the aspects of density, binding energy, radial distribution function (RDF), solubility parameters, trigger bond length and mechanical properties. As can be seen from the results of RDF that the ADN/fluoropolymer blends possess stronger intermolecular interaction and higher stability due to hydrogen bonds and vander Waals forces. The maximum bond lengths of trigger bonds of ADN/fluoropolymer blends are significantly reduced (compared with pure ADN), which indicates that the safety of ADN/fluoropolymer blends is better than that of ADN. From the results of density, binding energy and solubility parameters, it can be seen that ADN has brilliant interaction and better compatibility with PTFE and F26, while the interaction between ADN and PVDF is weak with poor compatibility. Moreover, the addition of fluoropolymers can improve the mechanical properties of ADN. All the results show that PTFE and F26 are expected to be used as binders in ADN-based solid propellants.