Microcalorimetry and DSC study of the compatibility of energetic materials

This study included accelerated aging of cyclotetramethylene tetranitramine (HMX) and CH-S (>97% RDX), coating of HTPB propellant with two sealants (A, B) and reaction kinetics between cyclotrimethylenetrinitramine (RDX) and organic salt (ammonium benzoate). Isothermal microcalorimetry (IMC) analyses at 55-75 degreesC and DSC analyses at decomposition temperatures (180-300 degreesC) were in agreement regarding compatibility. IMC heat Row measurements indicated that aging conditions did not affect HMX and CH-6. DSC rates of reaction at 200 degreesC were similar and thus indicated no reaction. DSC onset of reaction and IMC heat flow measurements showed that one sealant (A) had an interaction with the HTPB propellant while the other did not. When the sealants were combined their reaction with HTPB decreased as the amount of sealant B increased. Reruns of HTPB with sealants A and sealants A + B after 3 weeks at room temperature showed that there was still an additional reaction of similar to9%. IMC and DSC kinetic analyses were carried out on HTPB propellant + sealant A admixture. IMC gave a value of 5 kcal/mol for the reaction in the 55-75 degreesC region while DSC measured the decomposition reaction where the activation energy was lowered from 48 kcal/mol for the propellant to 43 kcal/mol for the admixture. DSC kinetic study of RDX + organic salt showed a shift of the RDX peak temperature from 217 degreesC (neat RDX) to 180 degreesC (admixture). The activation energy for decomposition of the admixture was 25 kcal/mol, Literature values for neat RDX is 47 kcal/mol. Thus DSC kinetic data indicated that the admixture was incompatible at elevated temperature. An IMC kinetic study at temperatures from 65 to 77 degreesC for this admixture gave a value of 33 kcal/mol. The reaction mechanism in the DSC and IMC experiments may be different since in the former case it involves a reaction between a gas (NH3) and a liquid (RDX) while in the latter case it involves a gas (NH3) and solid RDX which is a much slower reaction as also reflected in the higher activation energy. (C) 2001 Published by Elsevier Science B.V.