Preparation And Properties Of RDX-based High Energy Propellants

In order to improve the mechanical properties of high energy nitramine propellants,a series of high energy propellant formulations with GAP-based thermoplastic elastomers and nitrocellulose as binders and RDX as high-energy oxidants were designed,and the preparation process was determined.The effects of the proportion of GAP-based plastic elastomers and nitrocellulose,the particle size and the content of RDX on the energy performance,mechanical properties,thermal decomposition kinetics,and thermal expansion coefficient of high energy propellant were analyzed and discussed.The main findings are as follows:The theoretical calculation results of the energy characteristic parameters show that partial replacement of nitrocellulose with GAP-based energetic thermoplastic elastomers can reduce the explosion temperature of the propellant and increase the specific volume and the residual capacity.While increasing the content of the RDX could significantly increase the energy level of the system.Therefore,the unity of the high energy level and low detonation temperature of the propellant can be achieved by adjusting the formulation components.When the content of RDX is 60% and GAP-ETPE/NC ratio is1:1,the force constant of propellant can reach 1186 kJ/kg and the explosion temperature is 3075 K.DSC test results show that the GAP-based thermoplastic elastomer has good compatibility with nitrocellulose.And there is no obvious interaction with the solid phase of RDX,but it will advance the main decomposition peak temperature of RDX.The RDX-based high energy propellant samples were prepared by extrusion molding at room temperature.The volume ratio of ethyl acetate/acetone in the mixed solvent is 1:1.The ratio of solvent to binder is from 2:1 to 3:1,and the kneading time is 2 ~3h.The mechanical properties test results show that the GAP-based energeticthermoplastic elastomer has obvious toughening effect on high-energy propellant.With the increase of GAP-ETPE/NC ratio in the binder,the axial compressive strength and solid surface energy of the propellants decrease gradually.And the impact strength gets improved.The smaller particle size of RDX is,the higher mechanical strength and solid surface energy could be.The compressive strength of the propellants increase as the content of RDX increases,the main force of which is the mechanical reinforcement of the solid filler particles,but not its interaction with the binder system.The thermal decomposition process of RDX-based high energy propellant samples features significant thermal decomposition characteristics of the RDX.And it can be divided into two stages mainly: the thermal decomposition of nitrocellulose and the melting decomposition of RDX.The activation energy,pre-exponential factor,activation enthalpy and activation entropy of the thermal decomposition reaction of RDX-based high energy propellant all increase gradually as the GAP-ETPE/NC ratio increases.And the thermal stability gets improved obviously.While the varied particle size of RDX has little influence on the thermal stability of RDX-based high energy propellant.The propellant with higher content of RDX shows better thermal stability.The composition of binder system and the content of RDX are the main factors affecting the linear expansion coefficient of propellants.The linear expansion coefficient of the RDX-based high energy propellant gradually increases with the increased ratio of GAP-ETPE/NC,and decreases with the increased content of RDX.The change in the particle size of RDX has little effect on the linear expansion coefficient of high energy propellants.