Design,Synthesis And Properties Of A New Borate Ester Bonding Agent NBBA

HTPB component?HTPB/AP/RDX/Al?composite solid propellant is widely used in the rocket engine for its excellent comprehensive properties,but the solid content in the formula is high,which leads to the poor performance of the propellant charging process and the poor mechanical properties of the propellant.The bonding agent in use can not solve this problem completely.in which the second-generation boronic acid ester bonding agent BEBA-4 has good bonding effect,but there is still a problem that the mechanical properties fluctuate due to changes in the environment temperature and humidity.In view of this background,a new type of boronate ester bonding agent was developed.In view of the deficiency of the existing boronate ester bonding agents,this paper proposes the principle of“multi-center,multi-functional”bonding agent design and design a novel structure of polyamine and multi-boron bonding agent to ensure that the new boronate ester bonding agent interact on both RDX and AP,which not only increases the site of bond interaction,but also improves the hydrolytic stability of the boron ester structure.1,4,7-Triazaheptane and three cycloboronate intermediates were synthesized and NBBA bonding agents were obtained by transesterification.1,4,7-Triazaheptane was synthesized from diethylenetriamine and 2-chloroethanol as the backbone intermediates of NBBA.Single factor experiments and orthogonal experiments were combined to optimize the ratio of raw materials and reaction conditions.The ratio is:the molar ratio of diethylenetriamine to 2-chloroethanol is 1:6.5;the optimum process conditions are:the reaction temperature is 85°C,the reaction time is 5 h,the yield reaches 98.76%,and the structure of the product is characterized by,FT-IR,¹H-NMR,ES-MS and the determination of hydroxyl value,amines value.Three kinds of boron ester intermediates were synthesized with boric acid and various diols,and their structures were characterized by ¹H-NMR.Three kinds of polyamine multi-boron bonding agent NBBA were synthesized by transesterification of the intermediate of1,4,7-Triazaheptane and boric acid ester.The performance of three kinds of NBBA was analyzed from the aspects of hydrolysis resistance,NH₃ absorption and mechanical properties.NH₃ absorption properties of three kinds of NBBA are good,while NBBA-3 has the best hydrolysis resistance,low viscosity and good process performance.The test results show when NBBA-3 applied to HTPB four component propellant,the maximum tensile strength at room temperature reached 0.83 Mpa,the maximum elongation 58%;the maximum tensile strength of high temperature reached 0.52 Mpa,and the maximum elongation66%,meeting the requirment of the engine design.