Research On The Mechanical Properties Of High-plasticized High-energy Solid Propellants

As the power source of missile and aerospace engine,solid propellant is the key technology of weaponry.Its mechanical properties affect energy release and then limit the range of application.In order to satisfied the high energy requirement of the advanced missile weaponry,GAP/CL-20 high-energy solid propellant was obtained by using energetic binder GAP and high-energy explosive CL-20.GAP/CL-20 high-energy solid propellant had the highest energy in present applied propellants,but its basic mechanical properties were poor and adjustable methods were limited.In this paper,the influencing laws of the components on the mechanical properties of GAP/CL-20 high-energy solid propellant were investigated,the main influencing factors and their influencing mechanisms were revealed,and the effective methods were put forward by research conclusions.The influencing laws of components on the mechanical properties of GAP/CL-20high-energy solid propellant were studied through uniaxial tensile test.It was revealed that the binders,bonding agents,plasticizers and the plasticizing ratio were the main influencing factors.The maximum tensile strength of propellant increased from 0.39 MPa to 0.45 MPa,and the maximum elongation increased from 98.3%to 417.7%with PEG replacing GAP.The maximum tensile strength of propellant decreased from 0.62 MPa to0.30 MPa,and the maximum elongation increased from 48.2%to 84.4%with Bu-NENA replacing NG/BTTN.When NG/BTTN was plasticizer,the maximum tensile strength of propellant decreased from 0.62 MPa to 0.39 MPa,and the maximum elongation increased from 48.2%to 98.3%with the plasticized ratio increasing from 1.0 to 3.0.The maximum tensile strength of propellant increased from 0.13 MPa to 0.39 MPa,and the maximum elongation decreased from 233.4%to 98.3%with adding NPBA.Inverse gas chromatography and contact angle method were used to investigate the surface properties of main components and the interaction among them.It was revealed that the adhesive work between GAP matrix and CL-20,70.69 mJ·m^-2,was lower than 98.61mJ·m^-2 between PEG matrix and HMX,which indicated that the interaction between GAP matrix and CL-20 was inferior to that between PEG matrix and HMX.The binding energy between binder and explosive was calculated by molecule dynamics.It was revealed that the binding energy between PEG and HMX,456.48 kJ·mol^-1,was 76.03%larger than259.32 kJ·mol^-1 between GAP and CL-20,which meant the interaction between GAP and CL-20 was inferior to that between PEG and HMX.The influence of interface phase structural changes was analyzed through dynamic mechanical analysis.The ratio of contribution to tanδbetween interface phase and binder matrix was indicated by parameter A.The cohesive situation was poor when parameter A was small.The parameter A of GAP/CL-20 propellant,13.15,was larger than 4.91 of PEG/CL-20 propellant and 10.24 of GAP/HMX propellant at room temperature,so that the cohesive situation of GAP/CL-20propellant was poor.In situ tension process of propellant was observed through scanning electron microscope.The results showed that it was easy for particles of GAP/CL-20propellant to dewet and the expanding rate of dewetting was faster than that of PEG/CL-20propellant.This paper uncovered that the inferior interaction between GAP matrix and CL-20 was one of fundamental reasons that caused poor mechanical properties of GAP/CL-20 high-energy solid propellant.According to the results of influencing laws and mechanisms,both physical and mathematical models of the mechanical properties of GAP/CL-20 high-energy solid propellant were established.The mathematical model was based on the state equation of high elastic polymer,and the physical model was based on cross-linking model of propellant.The characteristics of GAP/CL-20 propellant such as high plasticized ratio,rigid GAP molecule chain and the interaction between GAP matrix and CL-20 were all considered when established the models.And they were analyzed that rigid GAP network structure and inferior interaction between GAP matrix and CL-20 were fundamental reasons which caused poor mechanical properties of GAP/CL-20 propellant.Based on the research results,the regulative methods were put forward from aspects including binder structure and interface interaction,which were proved by adding NPBA binding agent and G-GAP binder with high molecular weight.