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

Abstract

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. 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.

Enhancing energy release of aluminized propellants and explosives through fluorinated binder

“…According to our previous work [26], the decomposition of fluorine‐modified HTPE produces highly oxidizing fluorine fragments. These fragments react with Al to produce AlF 3 with a low boiling point, which serves to reduce the agglomeration of molten Al particles [29].…”

Enhancing the combustion of nAl with AlF3 coating: gas–solid reaction mechanism for reducing combustion agglomeration of Al powder

“…[19][20][21] Among these methods, surface modification of nAl particles with fluorine-containing coating materials has been identified as an effective way to avoid combustion agglomeration for improved energy output. 14,[22][23][24] Fluoropolymers or organic fluorides, such as Viton, 25 polyvinylidene fluoride (PVDF), 26 polytetrafluoroethylene (PTFE), 27,28 perfluoropolyether and its derivatives, [29][30][31] release HF, C x H y F + and F + fragments during the combustion process. These oxidizing fragments react with the inert Al 2 O 3 layer to release AlF 3 .…”

Effect of Fluoroalcohol Chain Extension Modified HTPB Binder on the Combustion Performance of Aluminized Propellants

“…When used as propellant matrixes, especially for propellants that need to be loaded under extreme conditions, HTPB binders are expected to possess excellent mechanical properties. The tailoring of mechanical properties can be accomplished by employing bonding agents to modulate the interfacial bonding between fillers and binders [6] and by adjusting the binder's network structure via the use of curing agents, crosslinking agents, and chain extenders [7,8]; of these, chain extension stands out as a straightforward and efficient method. Commonly used chain extenders include small-molecule diol or diamine chain extenders [9] such as 1,4-butanediol, ethylene glycol, and 2,4-diamino-3,5-dimethylthiotoluene.…”

“…The application of liquid fluorinated binders can safeguard the original solid content while improving the combustion efficiency of the Al powder. Shen et al [8,19] prepared hydroxylterminated polyether polyurethane elastomers grafted with fluoroalcohols and added this preparation to aluminized propellant, which also effectively alleviated the Al powder agglomeration and promoted energy release.…”