Nonisothermal decomposition and safety parameters of HNIW/TNT cocrystal.

To explore the thermal decomposition behavior and evaluate the thermal safety of the cocrystal 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW)/2,4,6-trinitrotoluene (TNT), its thermal and kinetic behaviors were studied by differential scanning calorimetry (DSC) technique. With the help of onset temperature (T (e)) and maximum peak temperature (T (p)) from the non-isothermal DSC curves of HNIW/TNT cocrystal at different heating rates (β), the following were calculated: the value of specific heat capacity (C (p)) and the standard molar enthalpy of formation , the apparent activation energy (E (K) and E (O)) and pre-exponential constant (A (K)) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method, density (ρ) and thermal conductivity (λ), the decomposition heat (Q (d), as half-explosion heat), Zhang-Hu-Xie-Li's formula, Smith's equation, Friedman's formula, Bruckman-Guillet's formula, Frank-Kamenetskii's formula and Wang-Du's formulas, the values (T (e0) and T (p0)) of T (e) and T (p) corresponding to β → 0, thermal explosion temperature (T (be) and T (bp)), adiabatic time-to-explosion (t (tiad)), 50% drop height (H (50)) for impact sensitivity, critical temperature of hot-spot initiation (T (cr)), thermal sensitivity probability density function [S(T)] vs. temperature (T) relation curves with radius of 1 m and ambient temperature of 300 K, the peak temperature corresponding to the maximum value of S(T) vs. T relation curve (T (S(T)max)), safety degree (SD) and critical ambient temperature (T (acr)) of thermal explosion. Results show that the kinetic equation describing the exothermic decomposition reaction of HNIW/TNT cocrystal is The following thermal safety parameters for the HNIW/TNT cocrystal are obtained: T (e0) = 464.45 K; T (p0) = 477.55 K; T (be) = 472.82 K; T (bp) = 485.89 K; t (tiad) = 4.40 s, 4.42 s, and 4.43 s for n = 0, 1, and 2, respectively; T (cr) = 531.90 K; H (50) = 19.46 cm; and the values of T (acr), T (S(T)max), SD and P (TE) are 469.69 K, 470.58 K, 78.57% and 21.43% for sphere; 465.70 K, 470.58 K, 78.17% and 21.83% for infinite cylinder; and 459.39 K, 464.26 K, 77.54% and 22.46% for infinite flat.