Conductance method for determining the mechanical properties of propellants

TLDR: In this article, a solid propellant grain is converted from a nonconductive filled elasto into a highly-conductive fill elastomer by introducing an effective amount of an alkali metal tungstate or the analogous ammonium salt which, in addition to imparting electrical conductance characteristics, also functions as an oxidizer in the propellant composition.

Abstract: A solid propellant grain is converted from a non-conductive filled elasto into a highly-conductive filled elastomer by introducing an effective amount of an alkali metal tungstate or the analogous ammonium salt which, in addition to imparting electrical conductance characteristics, also functions as an oxidizer in the propellant composition. When sodium tungstates, known as tungsten bronzes, or the analogous ammonium salt, are used to replace from 1 to 3 parts of the ammonium perchlorate oxidizer in the propellant formulation, it changes the grain to a highly-conductive grain, and, thereby, permits measuring the continuity of the propellant grain by means of electrical conductance measurements. These conductance measurements provide means of assessing the changes which take place in the solid propellant grain, such as, the physical and chemical changes (which affect mechanical properties) which the grain has undergone during storage or aging or when the grain is subjected to different load conditions, such as, acceleration, blast, shock, etc. In addition to the benefit of the reliable means for assessing such changes, the propellant grains employing the tungstates show an unpredicted increase in the propellant burning rate. The propellant density also increased due to the high density of the tungsten bronzes, and this is another benefit.