Influence of Fluorinated Polyurethane Binder on the Agglomeration Behaviors of Aluminized Propellants


In this study, fluorinated polyurethane (FPU) was prepared from dialcohol-terminated perfluoropolyether as a soft segment; isophorone diisocyanate (IPDI) as a curing agent; 1,2,4-butanetriol (BT) as a crosslinker; and 1,4-butanediol (BDO) as a chain extender. Fourier transform infrared spectroscopy (FTIR) and 1H NMR were used to characterize the structure of the FPU. The mechanical properties of the FPUs with different BDO and BT contents were also measured. Get more news about polyurethane binder,you can vist our website!
The tensile strength and breaking elongation of the optimized FPU formula were 3.7 MPa and 412%, respectively. To find out the action mechanism of FPU on Al, FPU/Al was prepared by adding Al directly to FPU. The thermal decomposition of the FPU and FPU/Al was studied and compared by simultaneous differential scanning calorimetry-thermogravimetry-mass spectrometry (DSC-TG-MS). It was found that FPU can enhance the oxidation of Al by altering the oxide-shell properties. The combustion performance of the FPU propellant, compared with the corresponding hydroxyl-terminated polyether (HTPE)-based polyurethane (HPU) propellant, was recorded by a high-speed video camera. The FPU propellants were found to produce smaller agglomerates due to the generation of AlF3 in the combustion process. These findings show that FPU may be a useful binder for tuning the agglomeration and reducing two-phase flow losses of aluminized propellants.
Polyurethane binder is an important component of composite solid propellants, which function as a matrix to provide dimensional stability for filler particles [1,2]. The evolution of composite solid propellant energy performance is usually accompanied by the innovation of the binder system. As the binder evolved from the initially developed bituminous to hydroxyl-terminated polybutadiene (HTPB) and hydroxyl-terminated polyether (HTPE), the specific impulse of the propellants increased gradually from 176 to 270 s [3,4]. Although these new composite solid propellants have superior energy performance, the agglomeration of aluminum combustion, usually existed in these high-aluminized HTPB and HTPE propellants, often brings a series of nonignorable problems [5,6,7]. The agglomeration of Al prolongs the combustion interface between aluminum and oxygen, resulting in incomplete thermal energy conversion and high two-phase flow losses [8,9]. It has been reported that for every 10% of unburned Al, the specific impulse (Isp) loss is approximately 1% [10]. Moreover, the agglomeration of Al also causes adverse effects on the working process of the motor system, such as slag accumulation, nozzle erosion, and unsteady motion inside the combustion chamber .