Thermal Behavior,Nonisothermal Decomposition Reaction Kinetics of Mixed Ester Double-base Gun Propellants

The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by thermogravimetry（TG） and differential thermogravimetry（DTG）, and differential scanning calorimetry（DSC） under the high-pressure dynamic ambience. The results show that the thermal decomposition processes of the mixed nitric ester gun propellants have two mass-loss stages. Nitric ester evaporates and decomposes in the first stage, and nitrocellulose and centralite II（C2） decompose in the second stage. The mass loss, the DTG peak points, and the terminated temperatures of the two stages are changeable with the difference of the mass ratio of TEGDN to NG. There is only one obvious exothermic peak in the DSC curves under the different pressures. With the increase in the furnace pressure, the peak temperature decreases, and the decomposition heat increases. With the increase in the content of TEGDN, the decomposition heat decreases at 0.1 MPa and rises at high pressure. The variety of mass ratio of TEGDN to NG makes few effect on the exothermic peak temperatures in the DSC curves at different pressures. The kinetic equation of the main exothermal decomposition reaction of the gun propellant TG0601 was determined as： dα/dt=1021.59（1-α）3e-2.60×104/T. The reaction mechanism of the process can be classified as chemical reaction. The critical temperatures of the thermal explosion（Tbe and Tbp） obtained from the onset temperature（Te） and the peak temperature（Tp） are 456.46 and 473.40 K, respectively. ΔS≠, ΔH≠, and ΔG≠ of the decomposition reaction are 163.57 J·mol^-1·K^-1, 209.54 kJ·mol^-1, and 133.55 kJ·mol^-1, respectively.

Evaluation of Thermal Hazard of Composite Modified Double-base Propellant by Microcalorimetery Method

The thermal decomposition behavior of composite modified double-base（CMDB） propellant containing cyclotrimethylene trinitramine（RDX） was studied via a Calvet microcalorimeter at five different heating rates. The activation energy（E） and the pre-exponential factor（A） of two obvious exothermic processes were obtained by Kissinger＇s method and Ozawa＇s method. The entropy of activation（△S^≠）, the enthalpy of activation（△H^≠）, and the free energy of activation（△G^≠） of the first stage were calculated. To evaluate the thermal hazard of the RDX-CMDB propellant, the critical temperature of thermal explosion（Tb）, the self acceleration decomposition temperature（Tsgox）, the adiabatic decomposition temperature increment（ATad） and the time-to-explosion of adiabatic system（t） were presented as 145.3 ℃, 138.15 ℃, 1634 K and 583.71 s（n=0） and 586.28 s（n=1）, respectively.

Thermal Decomposition of Ammonium 3-Nitro-1,2,4-triazol-5-onate Monohydrate

The thermal decomposition of ammonium 3-nitro-1,2,4-triazol-5-onate monohydrate[NH4（NTO）·H2O] was studied by means of thermal analysis-MS coupling and the combination technique of in situ thermolysis cell with rapid-scan Fourier transform infrared spectroscopy. The results show that there are two endothermic steps and one exothermic step in the decomposition process of NH4（NTO）·H2O. The detected gas products consist of NH3, H2O, N2, CO2, CO, and NO2.

Estimation of Critical Temperature of Thermal Explosion for Energetic Materials Based on Non-isothermal Kinetic Equation dα/dt =A_0 exp(bT)[1+(T–T_0 )b]f(α)

Critical temperature（Tb） of thermal explosion for energetic materials is estimated from Semenov＇s thermal explosion theory and the non-isothermal kinetic equation da/dt=Aoexp（bT）[1＋（T-T0）b][（a） deduced via reasonable hypotheses, where To is the initial point of the deviation from the baseline of DSC curve. The final formula is （Tb-Te0）{ 1＋1/[1＋（ Tb-T00）b]}=1. We can easily obtain the initial temperature（T0/） and onset temperature（Tci） from the non-isothermal DSC curves, the values of Too and Tc0 from the equation TOi or ei=T00 or c0＋α1βi＋a2βi^2＋…＋aL-2L-2βiL-2, i=1,2,…L, the value of b from the equation： In[β/（Tei-T0i）]=ln[A0/G（a）]＋bTei, so as to calculate the value of Tb. The result obtained with this method coincides completely with the value of Tb obtained by Hu-Yang-Liang-Wu method.

Synthesis and characterization of poly(phthalazinone ether nitrile) (PPEN)-polydimethylsiloxane (PDMS) block copolymers

Block copolymers with different backbone compositions have been prepared by the condensation of dimethylamino terminated poly（dimethylsiloxane） （PDMS） and hydroquinone terminated poly（phthalazinone ether nitrile） （PPEN） in the presence of chlorobenzcne/N-methyl pyrrolidone （NMP） as solvents. The products were characterized by FTIR, ^1H NMR and gel permeation chromatography. Differential scanning calorimetry analysis indicated that the block copolymers showed separated microphase.

Theoretical Studies on Substituent Effect of the Reaction of Amide and Formaldehyde

The thermodynamic properties of the reaction of amide and formaldehyde were calculated via B3LYP method when substituents chosen included CH3,CH2CH3,CH2CH2CH3,CH2CH2CH2CH3,CH（CH3）2,CH2CH（CH3）2,CH（CH3）CH2CH3 and C（CH3）3.Based on the optimization of the structures for reactants and products,the thermodynamic functions of all the species for an actual state were obtained.The thermodynamic data and the equilibrium constants were investigated within a temperature range of 300―343.15 K.The calculated results show that the reaction is exothermic and spontaneous.The trends of all thermodynamic properties are consistent with the temperature.The preferential order of the substituent effect is CH2CH（CH3）2CH（CH3）CH2CH3CH2CH2CH2CH3 CH2CH2CH3CH2CH3≈CH（CH3）2C（CH3）3≈CH3.

Thermal Behavior, Specific Heat Capacity and Adiabatic Time-to-explosion of GDN

A new compound, [（NH2）2C=NH2]＋N（NO2）2-（GDN）, was prepared by mixing ammonium dinitramide （ADN） and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy（E） and pre-exponential constant（A） of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion（Tb） of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.

One-pot Synthesis of 2-Nitro-4,5-dicyano-1H-imidazole

In the last few decades,nitroimidazoles have been investigated mostly due to their properties as antibiotics,radiosensitizers and anti-protozoans[1 -3].Recently these nitroimidazoles,such as 2,4-dinitroimidazole,1-methyl-2,4,5-trinitroimidazole and their energetic salts, have attracted renewed attention for their favorable explosive performance as well as improved safety characteristics[4,5].Because of the activity of cyano group,2-nitro-4,5-dicyano-1 H-imidazole (NDCI) could be used as an intermediate in the synthesis of novel energetic materials containing nitroimidazole moiety.NDCI has been synthesized by the procedure given by Yixin Lu and coworkers[6],where the diazotization reaction and the Sandmeyer reaction were separately achieved.NDCI was obtained by adding a solution of sodium nitrite to 2-diazo4,5-dicyanoimidazole which was generated by diazotization of 2-amino-4,5-dicyano-1H-imidazole ( ADCI ) with sodium nitrite in water-hydrochloric acid and collected by filtration.Dry 2-diazo-4,5-dicyanoimidazole was so sensitive to shock that its separation may cause explosion[7].

A new approach to the synthesis of N-monosubstituted aniline and its derivatives viaβ-cyclodextrin host-guest complexes

A novel method for the synthesis of N-monosubstituted aniline and its derivatives via β-cyclodextrin （CD） host-guest complexes has been presented. The mild reaction gives the title compounds with high selectivity in good yields of 90-98%.

Synthesis, Crystal Structure and Thermal Behavior of 4,5-Diacetoxyl-2-（dinitromethylene）-imidazolidine

A new energetic material, 4,5-diacetoxyl-2-（dinitromethylene）-imidazolidine （DADNI）, was synthesized by the reaction of 4,5-dihydroxyl-2-（dinitromethylene）-imidazolidine （DDNI） and acetic anhydride, and characterized by single crystal X-ray diffraction. Crystal data for DADNI are monoclinic, space group C2/c, a= 15.9167（3）A, b= 8.6816（4）A, c=8.5209（3） A, t= 103.294（9）°, V= 1145.9（3） A3, Z=4,A=0.150 mm 1, F（000）=600, Dc= 1.682 gocm-3, R] =0.0565 and wR2=0.1649. Thermal decomposition behavior of DADNI was studied and an intensely exothermic process was observed. The kinetic equation of the decomposition reaction is：exp（-1.582 ×10^5/RT）. The critical temperature of thermal explosion is 163.76℃. The specific heat capacity of DADNI was studied with micro-DSC method and theoretical calculation method. The molar heat capacity is 343.30 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of DADNI was calculated to be 87.7 s.