The objective of this work was to develop and mature a resonant acoustic mixing (RAM) process to reduce the environmental, safety, and occupational health impacts currently observed in the manufacture of the high volume pyrotechnic: Magnesium/Sodium Nitrate/Epoxy. These formulations are found in a variety of munitions including gun- and mortar-fired illumination projectiles. Common production methods for these materials can require personnel to manually scrape impellers during the mixing process while exposing them to over a hundred pounds of known sensitive pyrotechnic materials. In addition to safety concerns, large quantities of toxic solvents (e.g., acetone) are used to clean the many parts of these 1950’s-era mixers (e.g., impeller or mix-muller mixers). Acetone poses environmental, occupational health, and safety risks, which make these processes unsustainable. The proposed RAM method could significantly reduce personnel hazards and solvent waste streams.
Three RAM processes were developed to reduce the environmental, safety, and occupational health risks currently observed in the mix-muller manufacturing process of Magnesium/Sodium Nitrate/Epoxy illumination compositions. In these processes, it was shown that the key mixing step is the incorporation of the high-viscosity cross-linking agent Versamid 140. All RAM mixed materials were observed to be more homogeneous with similar/slightly lower sensitivity than the mix-muller produced materials. Performance testing showed that resonant acoustic mixed material produced similar burn times and similar/increased luminous efficiency to a mix-muller produced composition. As many of the Resodyn methodologies developed utilize solvent to lower the viscosity of the epoxy precursors, a number of lower-viscosity, commercially-available epoxy alternatives were also subjected to mechanical testing, performance testing, and inert RAM processing evaluation. In short, a number of low-viscosity curing agent alternatives appear to have promising RAM processing characteristics and minimal effect of combustion performance while being able to offer a range of mechanical properties to meet various application requirements.
For a pilot scale demonstration, the two-step RAM mix process was scaled from laboratory to concept scale (two lb. batch size) with no change in ignition sensitivity. In collaboration with Crane Army Ammunition Activity, three M485A2 illumination candles with RAM illumination composition were subjected to standard testing procedures along side candles that were produced with the standard mix-muller process. All three RAM candles performed similarly to their mix-muller counterparts and demonstrated that RAM is a viable alternative to mix-muller mixers.
A central benefit of RAM mixing is decreased operator exposure to production-scale quantities of sensitive explosives. Additional projected benefits of a production-scale RAM process may result in significant increases to overall throughput, labor cost reduction of 61-96%, and a reduction in acetone used for cleanup operations by over 99%.
Miklaszewski, E. J.; Yamamoto, C. M.; Mullins, M. L.; Shaw, A. P.,
“Safer Resonant Acoustic Mixing Methods for High-Volume
Production of Pyrotechnics” Joint Army-Navy-NASA-Air Force
Conference, May 2017.
Miklaszewski, E. J.; “Overview of Crane RAM Projects and
Capabilities”, 42nd TTCP Meeting, WPN TP-4, DSTL Porton
Down; 14 Feb 2017.
Moretti, J. “Future Pyrotechnics Focus Area”, 42nd TTCP
Meeting, WPN TP-4, DSTL Porton Down; 14 Feb 2017.