Synthesis And Characterization Of Ferric Perfluorooctanoate And Its Application In HTPB Propellant

During the combustion of the aluminized composite solid propellant,the aluminum particles agglomerate on the combustion surface,which leads to form large-sized liquid-phase aluminum-containing agglomeration.The large liquid-phase aluminum-containing agglomeration in the combustion process will cause many problems,such as the two-phase flow loss,slag deposition and the ablation of the insulation layer of the rocket motor,even the block of the nozzle throat,which will cause serious consequences.Therefore,decreasing agglomeration of aluminum powder is of great importance to improve the comprehensive performance of aluminum-containing HTPB propellant.In this paper,ferric perfluorooctanoate?Fe?PFO?₃?was synthesized and its structure and properties were characterized.Firstly,the effect of Fe?PFO?₃ on the thermal decomposition of ammonium perchlorate was studied.Secondly,the effect of Fe?PFO?₃ on the thermal properties of HTPB propellant and its components were studied.Finally,the effect of Fe?PFO?₃ on HTPB propellant combustion and the mechanism of action were carefully studied.Fe?PFO?₃ can remarkably reduce the pyrolysis temperature of ammonium perchlorate?AP?,and increase the total heat release.The addition of 1%,2%,5%and10%Fe?PFO?₃ can reduce the pyrolysis temperature of AP by 6°C,20°C,60°C and67°C,respectively.Among them,the addition of 2%Fe?PFO?₃ reduced the activation energy of AP pyrolysis by 38 kJ.mol^-1.Fe?PFO?₃ can promote the thermal decomposition of HTPB propellant samples,and slightly delay the thermal decomposition of the HTPB binder system.The results of thermal analysis show that Fe?PFO?₃ can significantly increase the weight gain of the reaction of Al powder with air,and increase the reactivity of Al powder with air.The addition of Fe?PFO?₃ can reduce the explosion heat of HTPB propellant samples and increase the burning rate.The condensed phase combustion products were characterized by XRD,SEM and particle size analysis.The results show that Fe?PFO?₃ can reduce the relative content of?-Al₂O₃ and?-Al₂O₃ in the condensed phase combustion products and increase the relative content of?-Al₂O₃.Fe?PFO?₃ can reduce the condensed phase combustion products of large particle size and significantly weaken the agglomeration of the condensed phase combustion products.Fe?PFO?₃ can not only reduce the particle size of the condensed phase combustion products,but also narrow the particle size distribution of the condensed phase combustion products.Fe?PFO?₃ can depress the agglomeration of the condensed phase combustion products of HTPB propellant,the mechanism study points that the fluorine-containing material produced by the decomposition of Fe?PFO?₃ can react with the oxide layer on the surface of Al powder to produce AlF₃,which leads to the crack of the oxide layer on the surface of Al powder,so that the internal active aluminum can react with the external oxidizing material,thereby improving the combustion efficiency of the Al powder and reducing the agglomeration of the condensed phase combustion products.