Study On Basic Properties Of A Novel Nitroglycerin-Free Cross-linked Double Base Propellant

Cross-linked modified double base propellant has been considered as an important propellant for its excellent comprehensive properties.For traditional cross-linked modified double base propellant,nitroglycerine(NG)is used as the plasticizer.However,the high sensitivity and volatility of nitroglycerine make it a dangerous material for related personnel.Thus using less or no NG has become the development trend of double/modified double base propellant.In this paper,the novel low melting point insensitive energetic plasticizer has been used as the substitute of NG and the formula system of such nitroglycerine-free cross-linked modified double base propellant has been designed.The effect of different components on the performance of propellants and its variation law has also been studied in this paper.The main research works are as follows:The energetic property of nitroglycerine-free cross-linked modified double based propellant has been calculated and the effects of GAP content,plasticizer content,solid content,new energetic materials on the energetic property of propellant have been also investigated in this paper.The results indicated that standard theoretical impulse decreased when GAP content increased;impulse decreased a little when GAP content was in the range of 0~40% and the GAP content in blinder should be controlled below 40%.When AP was replaced by CL-20,characteristic signal of propellant decreased apparently while its energy maintained relatively high.Based on these facts,the formula of nitroglycerine-free cross-linked modified double based propellant was initially identified.The preparation and property of GAP modified spherical propellant which is the main component of nitroglycerine-free cross-liked modified double based propellant have been studied.NC spherical propellant and GAP modified spherical propellant was prepared successfully using Breath Figures method and internal solution method.The results of TG test showed the decomposition of GAP modified propellant consists of two stages and thermal degradation activation energy of the two stages were 242.65kJ/mol and 167.83 k J/mol,respectively.The results of sensitivity test showed that friction sensitivity of GAP modified spherical propellant was lower than that of single based spherical propellant,and the impact sensitivity of GAP modified spherical propellant was higher than that of single based spherical propellant.The effect of three plasticized systems including GAPA/TEGDN,BuNENA and BDNPF/A on the technology,mechanical property and thermal decomposition property of propellant have been studied.The results showed the technology property and mechanical property of the propellant in which BuNENA was used as plasticizer was the best,whose glass transition temperature was the lowest.Thus BuNENA is selected as the plasticizer of nitroglycerine-free cross-linked modified double based propellant.The rheokinetics has been used to study the cure process and mechanism of GAP modified special propellant.It has been found that the cure mechanism of GAP modified special propellant under isothermal conditions accords with crystallization growth and nucleation kinetic mechanism.The apparent activation energy of IPDI/GAP modified special propellant cure system is 65~77kJ/mol and apparent activation energy increased when TPB was used as the catalyst,compared with the catalyst DBTDL.It has also been found that Al hindered the cure process of GAP modified special propellant and lead phthalate(combustion catalyst)catalyzed the cure process while lead oxide,copper oxide and adipic acid copper had no effect on the cure process of GAP modified special propellant.The effect of the GAP content,cure parameter R,cure temperature and the amount of catalyst on the mechanical property has been investigated.It has been found that adhesive system possesses the optimum mechanical property under the conditions that the content of GAP is 30%,cure temperature is 50℃,R=1 and the amount of catalyst is around 0.2%~0.4%.The effect of 22# bonding agent and carbon fiber on the mechanical property has been studied.It has been found that 22# bonding agent improved the tensile strength and the elongation of propellant obviously while carbon fiber enhanced the tensile strength but had no effect on the elongation.The content of CL-20 also has effect on the mechanical property.The propellant possesses excellent mechanical property for which tensile strength is 0.39 MPa and the elongation is 58% when the content of CL-20 is 42%.The thermal decomposition property of propellant has been studied.The results indicated that the thermal decomposition of adhesive film can be divided into three stages.The first stage is the decomposition and fracture of nitrate groups and carbamate groups.Then the azide group begin to decompose.And the third stage is the cracking of molecular chain framework.Thus the optimum model of such adhesive film is the model of D4.The first decomposition loss peak of propellant increased while the second one decreased as the content of CL-20 increased.The optimum kinetic model of decomposition for such propellant accords with B1-D4 model.For nitroglycerine-free cross-linked modified double base propellant,the mixture of CL-20 and RDX is a low eutectic system which results in the cryogenic liquefaction and the advance of decomposition temperature for CL-20.The decomposition mechanism of CL-20 is mainly based on the decomposition of C-N bonds.Carbon fiber can improve the decomposition heat of propellant obviously when the carbon fiber is used as the substitute of carbon black which indicates the favorable regulation of carbon fiber on the combustion performance of propellant.