Theoretic Studies Of The Aging Reactions Of Nepe Propellant

Density functional theory method was used to study various aging channels of nitrate ester plasticized polyether (NEPE) propellants, mainly for the decomposition mechanisms of some plasticizers and polymer binders among them. Main parts of the thesis are as follows:1. The B3LYP/6-311G**method was employed to invesitgate the decomposition mechanism of a plasticizer nitroglycerin (NG). Two possible decomposition paths are found:(I) The O-NO2bond in NG was homolytically fractured to form·NO2and CH2ONO2CHONO2CH2O·, which subsequently decomposes to form·CHO,·NO2, and2CH2O;(Ⅱ) NG decomposes by successive HONO eliminations to form HONO and CHO-CO-CHO, which subsequently decomposes to form CH2O+2CO2and·CHO+CO. The rate constants of the initial process of the two decomposition channels indicate that the O-NO2cleavage pathway is easier to occur than the HONO elimination.2. The unimolecular decomposition channels of another plasticized1,2,4-butanetriol trinitrate (BTTN) were studied at the level of6-311g**level. We find two main mechanisms: First, the O-NO2hemolysis was happened to form·NO2and CH2ONO2CHONO2CH2CH2O·, which subsequently decomposes to form CH3CHO+·CHO+3NO2+HCHO; Second, successive HONO were eliminated to form three HONO and OHCCH2CHONO2CH2ONO2, which subsequently decomposes to form CH3CHO+2CO+3HONO.3. The B3LYP/6-31G*method was used to study the degradation mechanisms of the monomer (PT) of polyethylene glycol (PEG) polyurethane and four pathways are found:(a) The C-O homolysis in-NH-CO-O-of PT was happened firstly and the final products are INT100+-CH2OH+HCHO+TDI or2INT100+2HCHO;(b) PT firstly decomposes by intramolecular H-transfer reaction and the products are2TDI+glycol;(c) PT reacts with·NO2and·NO and the products are INT109+2HNO2;(d) PT reacts withs·NO2to form O-NO2and the products are INT105+2INT100.4. The decompositions of the monomer (HN) of hydroxyl terminated polybutadiene (HTPB) polyurethane were studied using the B3LYP/6-31G*and four pathways are found:(1) The C-O homolysis in-NH-CO-O-was happened firstly and the products are INT72+·CH2OH+CHCH+HCHO+INT70;(2) HN firstly decomposes by intramolecular H-transfer to form INT95+H2O+2INT72;(3) HN reacts with·NO2and·NO to form INT79+2HNO2;(4) HN reacts with·NO2to form O-NO2and finally to form2INT70+INT86.