Development of Mechanically Tunable Polythiourethane Elastomers for Recyclable Energetic Material

Composite propellants play a crucial role in rocket propulsion, particularly in the defense and aerospace industries. The proliferation of waste propellants from obsolete ammunition and recycled aircraft poses environmental and safety risks if not managed properly. In this work, a recyclable propellant was developed by using dynamic thiourethane chemistry. Trifunctional thiol trimethylolpropane tris(3-mercaptopropionate) (TMPTMP) was incorporated with hydroxyl-terminated polyether (HTPE) and isocyanate cross-linker to form a series of cross-linked polythiourethane (PTU) resins as alternative propellant binders. The PTU polymers have a relatively low glass transition temperature (T_g < −30 °C), which allows the material to function effectively across a broad temperature range. The mechanical performance of the PTU elastomers is highly tunable by adjusting the amount of TMPTMP. Moreover, energetic components, aluminon (Al), ammonium perchlorate (AP), and N-butyl nitroethyl nitramine (Butyl-NENA) were incorporated with PTU binders to form a three-component propellant. The composite propellant prepared with PTU elastomer contains only 0.054 wt % sulfur and is degradable and recyclable, enabling the recovery of all energetic components through appropriate methods. This approach provides a secure and effective solution for recycling components from waste energetic materials, paving the way for the next generation of propulsion systems characterized by economic benefits, energy efficiency, and eco-friendliness.