Novel segmented thermoplastic polyurethanes elastomers based on tetrahydrofuran ethylene oxide copolyethers as high energetic propellant binders

Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4-butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co-polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption-rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265 270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (< 393 K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion.