Simulation and experimental study on the incompatibility issue between ADN and isocyanate

Since solid composite propellants are composed of a high percentage of oxidizers, the search for green oxidizers such as ammonium dinitramide (ADN) as a substitute for non-eco-friendly ammonium perchlorate (AP) is an important issue. ADN/GAP propellants are good green candidates to replace conventional AP/HTPB propellants. The incompatibility issue of ADN with isocyanate curing agents of polyurethane binders is a well-known problem.

In this research, from the perspective of molecular dynamics and solubility parameter concept, an attempt was made to study molecular factors determining the preferable curing system for ADN/GAP composite propellants by examining the interaction energy between different isocyanate curing agents and ADN as well as GAP. From another standpoint, the aim is to show that the reactivity rate of different isocyanates with ADN has a significant difference, which has been investigated using molecular dynamics simulation and experimentally. The examined isocyanates include N100, IPDI, TDI, DDI, IPDI/N100, and DDI/N100. The activity of the selected curing system upon ADN was investigated using infrared spectroscopy at different time intervals and compared with the N100 as a conventional curing system. The results show that a meaningful improvement occurs using the selected curing system.