BAMO-THF copolymer-based energetic thermoplastic polyurethanes with a decent bonding property
Gang Tang, Zaijuan Zhang, Xiaoyu Li, Yunjun Luo
Abstract
Despite the high enthalpy of formation of poly(3,3-bis(azidomethyl)oxetane) (PBAMO), it is not readily applicable as a polymeric binder for propellants owing to its low chain flexibility and poor mechanical properties. The aim of this study was to improve the chain flexibility and mechanical properties of PBAMO binders by copolymerizing BAMO with tetrahydrofuran (THF) to produce a BAMO-THF copolyether (PBT). We report the preparation of energetic thermoplastic polyurethane elastomers (ETPUEs) by using PBT (soft segment), dicyclohexylmethylmethane-4,4′-diisocyanate (HMDI) (curing agent), a mixture of diols: diethyl bis(hydroxymethyl)malonate (DBM) (chain extender), 2-cyanoethyl-bis(2-hydroxyethyl)amine (CBA) (chain extender), and 1,4-butanediol (BDO) (chain extender). By systematically varying the content of the components, a series of ETPUEs was prepared. The results showed that with a fixed hard segment content, ETPUEs with CBA/BDO as chain extenders showed a stronger bonding property, lower glass transition temperature; improved mechanical properties (σm = 7.60 MPa, εb = 570.0%), and a higher enthalpy of formation (4015 kJ⋅mol−1). Moreover, when the ratio between CBA and BDO was 1:1, the binding strength between the binders and filler RDX was optimized, yielding a simulated propellant with decent mechanical properties (σm = 5.92 MPa, εb = 16.5%).