Theoretical and Experimental Studies on Thermal Behavior of 3-Methyl, 3-Carboxy, and 3-Nitro Substituted 1H,4H-6-nitro-pyrazolo[4,3-c]pyrazole

To evaluate the stability, heat-resistance ability and thermal safety of MNPP(1H,4H-3-methyl-6-nitro-pyrazolo[4,3-c] pyrazole), CNPP (1H, 4H-3-carboxy-6 -nitro-pyrazolo[4,3-c] pyrazole), DNPP (1H, 4H-3,6-dinitro-pyrazolo [4,3-c] pyrazole), the theoretical investigation on MNPP, CNPP and DNPP was performed by the DFT-B3LYP/6-31G level using Gaussian 09W program. The theoretical density (rho) of the compounds was obtained by quantum chemical method. The Kamlet-Jacobs formulas were employed to calculate the detonation properties including the detonation velocity (D) and pressure (P). Their thermal behaviors were investigated by Differential Scanning Calorimetry (DSC), Thermogravimetry-Derivative Thermogravimetry (TG-DTG) and in-situ cell thermolysis/Rapid-Scan Fourier Transform Infrared Spectroscopy (RSFT-IR). Results show that (1) using critical temperature of thermal explosion, free energy of activation of decomposition reaction and self-accelerating decomposition temperature as criterions, the thermal stability, heat resistance ability and thermal safety of the three compounds decrease in the order of DNPP > MNPP > CNPP, but using energy gap and total energy as criterions, the thermal stability decreases in the order of DNPP > CNPP > MNPP, therefore, DNPP is the most stable compound among the three compounds; (2) Among of the three compounds, DNPP possesses the maximum theoretical density (1.80 g.cm(-3)), the fastest detonation velocity (8.49 km.s(-1)) and the highest detonation pressure (31.96 GPa), suggesting that DNPP has good detonation properties and potential use in energetic material.