This work presents novel polyurethane (PU) formulations including bio-based polyether polyols produced in Romania (PETOL), evaluated as alternative binders for composite solid rocket propellants. Four PETOL products with different hydroxyl numbers and functionalities were reacted with the aliphatic isocyanate isophorone diisocyanate (IPDI), in the presence of either an inert plasticizer (dioctyl adipate, DOA) or an energetic plasticizer - triethylene glycol dinitrate (TEGDN). The resulting PU films were characterized using Fourier Transform Infrared (FT-IR) spectroscopy, thermal analyses, and mechanical testing, with several formulations exhibiting complete curing and favourable mechanical and thermal performance. The most promising binder was subsequently incorporated into composite propellant mixtures containing ammonium perchlorate, aluminium, and Fe₂O₃. The propellant grains were evaluated for density, safety characteristics (impact and friction sensitivity, vacuum stability), mechanical strength, and ballistic behaviour in subscale rocket motor tests. The selected formulation demonstrated a homogeneous microstructure, stable combustion, and a specific impulse of 204 s, comparable to conventional hydroxyl-terminated polybutadiene (HTPB)-based systems. These results highlight the potential of bio-derived polyols as cost-effective, locally sourced, and sustainable binders for advanced rocket propulsion applications.
Dîrloman et al. (Sun,) studied this question.