Determination of the kinetic data of the thermal decomposition of energetic plasticizers and binders by adiabatic self heating

Abstract

The thermal decomposition behaviour of the following plasticizers and uncured binders (diols for PUR-type elastomer binders) was investigated in solutions of toluene (with 10 mass% contents) by adiabatic self heating with an `accelerating rate calorimeter' (ARC ™): uncured GAP (poly-glycidylazide) from two manufacturers, polyGLYN (poly-glycidylnitrate) mixture (58.8/41.2 in mass%) N-methyl-/ N-ethyl-NENA (NENA = N-(2-nitratoethyl)-nitramine), DANPE (1,5-diazido-3-nitraza-pentane), GAPA (short chain GAP but with azido end groups), EGBAA (ethylene glycol-bis-(α-azidoacetate), octylazide (not for use in explosives), GAP-AA-2000 (normal GAP, but OH-end groups as esters of α-azidoacetic acid), GAP-AA-500 (short chain GAP, but OH-end groups as esters of α-azidoacetic acid). Three types of energetic groups are represented with these compounds: the organic nitric acid ester group, the nitramine group and the organic azido group. The closed measuring system prevents the solutions from evaporating and gives a good adiabaticity. The amount of the solution weighed-in was about 6 g, the measuring cells used are made from titanium with one inch in diameter. All named energetic substances would deflagrate after a short period of controllable self heating with the weighed-in amount of energetic substance. The advantage of the investigation of the solutions is that the decomposition of the energetic substances can be followed in a fully controlled way. With the self heat rate curves one can distinguish the plasticizers and binders with respect to the decomposition temperature range, the heat generation and the heat generation rate. The Arrhenius parameters and the released heats of reaction have been determined from the self heat rate curves, which have been described well with reactions of first order. The self heat rate curves have been scaled to the thermal inertia equal to one, which corresponds to (1) the measurement on a solution without measuring cell and to (2) the measurement on the energetic substance alone without solvent and measuring cell. The procedures of the scaling and of the data evaluation are described.