Experimental and simulation study of the phase separation of neutral polymeric bonding agent in nitrate ester plasticized polyether propellant and its application

Solid propellant is the key energetic composite material for weapons. Nitrate ester plasticized polyether (NEPE) propellant has shown the best energetic property among all propellants practically used at present, and neutral polymeric bonding agent (NPBA) is usually applied to improve its mechanical properties. However, the complex composition of propellant and explosive properties of nitrate plasticizers make the in-depth study of the cooling phase separation behavior and bonding performance of NPBA very challenging. In the present study, the phase separation behaviors of NPBA in different solution systems were studied by the turbidity method, and its adhesion degree onto solid filler caused by the phase separation was evaluated. The results show that high contents of AN in NPBA, high contents of inert solvents and high concentrations of NPBA are conducive to the phase separation. Based on the experimental results, a molecular dynamics simulation model for the cooling phase separation of NPBA in inert solvents is established, and applied to the phase separation of NPBA in the explosive nitrate plasticizer solution systems. The influences of the ratio of nitrate plasticizers, the ratio between plasticizer and binder, the concentration and molecular weight of NPBA, and the terpolymer composition of NPBA on the cooling phase separation were determined by the molecular dynamics simulation and verified with the experimental application of NPBA in the actual NEPE propellant system. Our work has provided a new strategy for the structural design and bonding performance evaluation of NPBA as the bonding agent for NEPE propellants, and constructed a novel structure-activity model to further guide its application study.