Stability and compatibility testing using a microcalorimetric method

Abstract

A microcalorimetric method is used for compatibility and stability studies. The high sensitivity of the instrument permits measurements at 60°C or even lower, i.e. under more realistic conditions than offered by conventional techniques like DTA and vacuum stability tests. The instrument consists of four independent calorimeters with a short thermal relaxation time, high sensitivity and excellent baseline stability. The calorimeters are placed in a common, precisely thermostated water bath. In compatibility studies, heat flow curves are recorded for the pure components and a mixture of these. A theoretical curve is constructed, which simulates a non-interacting system. The difference between the theoretical and the experimental curve for the mixture reflects the degree of interaction between the materials. A number of compatibility problems are discussed, including interactions in mixtures of TNT with amine/amide type polymers, polycarbonate — double base propellant interactions under various conditions and the influence of an anaerobic sealant on a high explosive and a propellant. Some results from stability measurements on an igniting compound are also presented.