Study On The Relationship Of Action Between Difluoroamino Binders And Boron

Boron has high calorific value and volume calorific value.The theoretical specific impulse of the boron-based fuel-rich propellant can reach 12000N·s·kg-1 However,boron has high melting point and high boiling point lead to the problems of poor ignition performance and low combustion efficiency,which affect its high energy performance in practical applications.The introduction of the difluoroamino binder is expected to use the active fluorine element in the difluoroamino group to promote the ignition and combustion of boron.Therefore,in this paper,the boron-based fuel-rich propellant as the basis,the effect of difluoroamino binders:poly(3-difluoroaminomethyl-3-methyloxetane)(PDF)and the copolymer poly(3-difluoroaminomethyl-3-methyloxetane)and 3,3-bis(azidomethyl)oxetane(PDB)and boron was studied by using thermal decomposition experiment,combustion experiments and modem instruments analysis technology.The main work is as follows:(1)The thermal decomposition characteristics,kinetics,pyrolysis and thermal decomposition products were studied by DSC,TG,PY-GC/MS,FTIR and TG-FTIR-MS analysis for PDF and PDB.The results showed that the thermal decomposition of PDF was composed of two thermogravimetric stages.The first stage is the two step of HF is not completely dissociated,and obtain the coexistent structure of CH=NF and C=N,the activation energy is 110～120 kJ mol-1;The second stage is the rest of the CH=NF thermal decomposition or rearrangement and the decomposition of polymer backbone.The main thermal decomposition of PDB phase is 180～290 ℃,the decomposition peak temperature were 222.44 ℃ and 256.35 ℃,the corresponding activation energy were Ek=119.2 kJ·mol-1,Eo=121.19 kJ·mol-1 and Ek=162.44 kJ·mol-1,EO =162.82 kJ·mol-1,l1nAK,23.24 min-1 and 30.14 min-1 respectively;the main decomposition of energy containing groups,and obtained the coexistence of CH=N and C=N.HF(g)was produced during the pyrolysis of PDF and PDB.(2)The decomposition characteristics of the mixture of PDF/B and PDB/B by DSC and TG,The change rules of pyrolysis and thermal decomposition products were studied by combining PY-GC/MS,FTIR,SEM-EDS and TG-FTIR-MS analysis methods.;The results showed that the main thermal decomposition stage PDF/B is 140～300℃,the main decomposition peak temperature is 216.49 ℃;the main stage the decomposition of PDB/B to 170～300 ℃,the decomposition peak temperature of 222.38 ℃ and 254.08 0C;The main decomposition phase of PDF/B and PDB/B occurs mainly by the thermal decomposition of the energetic groups and the redox reaction of the thermal decomposition products with boron.Because of the introduction of boron,the thermal decomposition initiation temperature of the mixed systems are earlier than that of the binders,but it does not affect the thermal stability of the system and the thermal decomposition way of the energetic group.During the thermal decomposition of the mixed systems,the thermal decomposition products of PDF and PDB and boron have the oxidation exothermic reaction,and the corresponding gaseous products are produced.(3)The propellant formulation was designed and optimized by theoretical calculation.The thermal decomposition characteristics,ignition and combustion characteristics of the propellant were studied by TG and DSC,laser ignition test and constant pressure combustion test respectively,he results show that in the boron fuel-rich propellant based on the difluoroamino binder,the initial peak temperature of thermal decomposition is 210.84 ℃,which is earlier than that of the traditional propellant.The introduction of PDB shortens the ignition delay time and promotes the ignition of the propellant in the ignition process,which is beneficial to the combustion of boron and the dispersion of boron products in the combustion process.The burning heat of the propellant was improved.