Synthesis And Applications Of Modified Boric Acid Ester Bonding Agents

Hydroxyl-terminated propellant, being an important kind of composite solid propellant, is often used in various kinds of large engines and it carries such characteristics as being inexpensive and energetic. Scientists have already developed different formulas to produce Hydroxyl-terminated propellant. With the development of modern defence technology, Hydroxyl-terminated propellant is required to have faster combustion rate and less combustion smoke.The high-energy hydroxyl-terminated propellant is enough to meet the operating requirement of engines, but its adhesives and its fillers are easy to be separated due to the high ratio of solid content in the propellent formulation which weakens the propellant’s mechanical property and limts the application of the high-energy hydroxyl-terminated propellant. We can add some boric acid ester bonding agent (BAG-5) to the formula which can enhance the propellant’s mechanical property. However, the propellant elongation percentage reaches at most50%, which fails to meet the operation requirement of engines. This thesis synthesized modified boric acid ester bonding agent via modified BAG-5. This modified boric acid ester bonding agent improves the mechanical property of butylated propellant which fulfills the demand of a certain kind of missile engine.Based on the function principle of boric acid ester bonding agent used in hydroxyl-terminated propellant, this thesis designed three modified boric acid ester bonding agents’molecular structures, namely, BAJ1series, BAJ2series and BAJ3series.This thesis choosed methyl acrylate, diethyl malonate, bromacetone and diethanol amine to synthesize three kinds of alcohol amine intermediates:N,N-two hydroxyethyl methyl propionate;N,N-two hydroxyethyl ethyl acetate formamide as well as N,N-two hydroxyethyl acetone. In this process, this thesis used orthogonal test and single factor analysis method to optimize the synthesis process of N,N-two hydroxyethyl methyl propionate as well as N,N-two hydroxyethyl ethyl acetate formamide. The optimal synthesizing technology for N,N-two hydroxyethyl methyl propionate requires that the molar ratio between methyl acrylate and diethanol amine to be1.2.Also, its reaction temperature should be controlled around40℃and its response time requires as long as3hours. Under this process, the reaction product will be light yellow sticky liquid and its production ration reaches92.2%.Comparably, the optimal synthesizing technology for N,N-two hydroxyethyl ethyl acetate formamide requires that the molar ratio between diethyl adipate and diethanol amine to be1.1:1. And the percentage of zinc acetate in diethanol amine should be controlled around0.3%. Its reaction temperature should reach as high as120℃and its response time is2hours. Under this process, the reaction product will also be light yellow sticky liquid and its production ration reaches88.7%. In this process, I used the IR, H1NMR and C12NMR to manifest its structure. The product structure of methyl acrylate and diethanol amine is composed by N,N-two hydroxyethyl methyl propionate while the product structure of diethyl malonate and diethanol amine is composed by N,N-two hydroxyethyl ethyl acetate formamide.Meanwhile, the thesis used polyether, boric acid, diethanol amine and alcohol amine intermediates as raw materials to synthesize the BAJ modified boric acid ester bonding agent via the ester exchange reaction. This thesis tested the boron content, amine value, Hydroxyl value, moisture content, water ratio and the PH value of modified boric acid ester bonding agent. The test report shows that the reactive hydrogen in the agent is decreased, its PH is weak alkaline and its average water ration is under5%.The thesis applyied this modified BAJ boric acid ester bonding agent to the high-energy hydroxyl-terminated propellant to produce propellant samples, and estimate its performance via the test of its mechanical property. Compared with BAG-5bonding agent, BAJ bonding agent bears more advantages concerning its performance. The ester base, carbonyl base and amido bond improves the adsorption ability to propellant fillers. The BAJ2-2-l’s tensile strength of BAJ modified boric acid ester bonding agent is0.802MPa, and its elongation reaches60.3%which is beyond the degisn requirement of mechanical property of high-energy butylated four-group composite solid propellant, thus bringing some actual application value.