Research On Performance Of Polyamino And Polynitro Derivatives Of Pyridine And Their N-oxides And Formulations

2,6-Diamino-3,5-dinitropyridine-l-oxide(ANPyO) and 2,4,6-triamino-3,5-dinitropyridine (TNPyO) are the representative compounds of polyamino and polynitro derivatives of pyridine and their N-oxides are novel energetic materials. ANPyO and TNPyO may be potential insensitive high energy explosive candidates with low mechanical sensitivity and cost, good stability and heat resistance, and high energy. They have a wide applied future in the energetic material field.The fine samples of ANPyO or TNPyO were respectively prepared by recrystallization from the solvents of trifluoroacetic acid(CF3COOH), dimethyl sulfoxide(DMSO) and N,N-dimethyl formamide(DMF) in the paper. The properties of the samples of ANPyO and TNPyO were compared. Results show that the average particle sizes of ANPyO and TNPyO that were prepared by recrystallization from CF3COOH are the smallest, their BET specific surface area are respectively 0.454m2·g-1 and 2.760m2·g-1; The thermal analysis and thermal decomposition kinetics calculation indicate that the temperatures of the exothermic peaks of ANPyO(CF3COOH) and TNPyO(CF3COOH) are the highest, the results are respectively 370.69℃and 355.9℃at 10℃·min-1 heating rate, and their activation energy are respectively 279.63kJ-mol-1 and 303.15kJ·mol-1; Mechanical sensitivity of ANPyO and TNPyO that were prepared by recrystallization from CF3COOH are respectively the lowest.ANPyO and TNPyO were coated with fluorine rubber F2311 and nitrile-butadiene rubber(NBR) by means of solution-water suspending-distillation method. The structures and properties of ANPyO, TNPyO and coated samples were characterized by fourier transform infrared spectroscopy(FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermograimetry (TG), and mechanical sensitivity test. The results show that the decomposition peak temperatures of coated ANPyO and TNPyO are lower, decomposition heats are higher, decomposition depths are smaller than uncoated ANPyO and TNPyO; It is found that particles of ANPyO and ANPyO become bigger; In FTIR spectra, N-H and nitrogen atom in pyridine spectral characteristic absorption bands have shifted; Mechanical sensitivity of coated ANPyO and TNPyO become lower respectively. Energy and mechanical sensitivity performance of ANPyO and TNPyO can be improved by coating, the performance of ANPyO and TNPyO coated by F2311 are better than NBR.The thermal decomposition processes of ANPyO, TNPyO and their formulations were studied by TG curves at different heating rates. The thermal decomposition kinetic parameters, such as activation energy, pre-exponential factor and reaction order, and the mechanism functions of ANPyO, TNPyO and their formulations were obtained by the integral iso-conversional non-linear method and Ozawa's method. The results show that the thermal decomposition mechanism of ANPyO and TNPyO and their formulations are classified as random nucleation and growth of n=1. Adiabatic thermal decomposition of ANPyO, TNPyO and their formulations have been investigated using accelerating rate calorimetry. Kinetic parameters, such as activation energy, pre-exponential factor and reaction order are calculated using reaction rate method. Thermal safety of ANPyO, TNPyO and their formulations have been evaluated according to temperature, pressure and temperature rise rate in thermal decomposition and calculation results.Thermal decomposition processes of ANPyO were investigated by using, TG-DTG, TG-MS, coupling techniques and in-situ thermolysis rapid scan-FTIR coupling technique. Mechanism of ANPyO thermal decomposition was presented by tracking test gaseous and agglomerate productions and their change in the thermal decomposition. The results show that the thermal decomposition process of ANPyO can be divided into steps, the ring reaction occur between-NH2 and adjacent-NO2 of pyridine ring, and releasing NO in the first step, and then pyridine ring decompose and release CO, HCN and CO2 etc gases.Some heat resistant composite explosives composed of ANPyO, some polymer binders containing fluorin and little heat resistant plasticizer were prepared. The performance tests were conducted by measuring the heat resistance, formability, explosion energy and sensitivity. The results show that the ANPyO-based heat resistant composite explosives have good heat resistance and formability, indicating that heat resistant composite explosives can be used in the temperature range of 200～250℃; Their mechanical sensitivity is vicinal and lower than that of ANPyO individual explosive. Performance of formability, penetration and power capability of ANPyO applied in the petroleum perforator were tested, performance formability and penetration of formulations containing NBR are the best among the all formulations.Density functional theory calculations were performed on crystalline ANPyO. The conduct bands are generally quite flat, while the valence bands are degenerate. The carbon, oxygen and amino nitrogen atoms make up the narrow lower energy bands. While the carbon, amino nitrogen and atoms in nitro group make up the higher energy bands. Change of electronic charges for the decrease of the cell edge a and c are almost the same, but different from the decrease of the cell edge b, indicating an anisotropic effect related to compressions. The C-Nitro and the N-0 (N-oxide) bonds are the weakest, and tend to rupture upon external stimulation. The crystal lattice energy is predicted to be-166.03kJ/mol, after being corrected for basis set superposition error. The Mulliken population for the N-0 (N-oxide) bond in crystal is much smaller than that in molecule, indicating that the molecular packing weakens this bond. Judged by the fact of N-0 (N-oxide) bond being weaker than C-Nitro bond, ANPyO is sensitive to mechanic impact than 1,3,5-triamino-2,4,6-trinitrobenzene, which is in good agreement with experiment. The performances of ANPyO such as low sensitivity were illuminated from molecular level.In order to know the desensitizing efficiency of ANPyO on nitroamine explosives, ANPyO/RDX and ANPyO/HMX composites were prepared by crystal coating and mixing method respectively. The structures and properties of the samples were characterized by SEM, DSC, mechanical sensitivity and detonation velocity tests. Results show that ANPyO has a better coating on nitromine explosives in crystal coating than mixing method; The average particle sizes of the samples are situated between ANPyO and nitromine explosives; The decomposition peak temperatures of the samples are lower than that of nitromine explosives; Mechanical sensitivity of the samples are lower than that of nitromine explosives, and mechanical sensitivity of the samples in crystal coating decreased more significant. The nitromine explosives-based polymer bonder explosive(PBX) samples were manufactured with ANPyO deterrent and different rubber binder. The structures and properties of the samples were tested. Results show that mechanical sensitivity of PBX samples are lower than that of nitromine explosives, detonation velocity of PBX samples are distinct higher than ANPyO.