Performance and Aging of Mn/MnO₂ as an Environmentally Friendly Energetic Time Delay Composition

Abstract

The Mn/MnO2 reactive system was investigated as a suitable replacement for the traditional W/BaCrO4/KClO4/diatomaceous earth delay composition. The delay performance, ignition sensitivity, and aging characteristics were examined in aluminum microchannels similar in diameter to common delay housings (4.7 mm). Stoichiometries with measured combustion temperatures between 1358 and 2113 K were self-sustaining with combustion velocities ranging from 2.4 to 7.3 mm s–1. The Mn/MnO2 system produced less gas than W/BaCrO4/KClO4/diatomaceous earth compositions allowing consideration for use in sealed delay housings. Accelerated aging at 70 °C and 30% relative humidity for 8 weeks resulted in no measurable loss of performance. Safety characterization showed that this composition is not sensitive to ignition by friction or electrostatic stimuli. The combustion products (as determined by X-ray diffraction) appear to be benign based on current regulations. Therefore, the Mn/MnO2 system appears to be a suitable low gas-producing, nonsensitive, less toxic delay composition with good longevity.

Measurement and Modelling of Pyrotechnic Time Delay Burning Rates: Method and Model Development

“…Alternatively, two thermocouples can be used to provide both the start-and the end time triggers while simultaneously enabling continuous tracking of temperature profiles [4]. High speed cameras are suitable for compositions burning in open channels and in glass columns [5].…”

Review of Gasless Pyrotechnic Time Delays

“…The Mn/MnO 2 reactive system is not sensitive to ignition by friction or electrostatic stimuli [114]. Stoichiometries with measured combustion temperatures between 1358 and 2113 K were found to be self-sustaining with burning rates ranging from 2.4 to 7.3 mm s À1 .…”

“…Much progress has been made in the development of slow 'green' gasless compositions, e. g. B/Fe 2 O 3 [25], W/MnO 2 [28], and Si/ CaSO 4 [19]. Mn/MnO 2 [26,114] and Si/Bi 2 O 3 [20] offer 'green' medium-slow and medium-fast burning options respectively. Missing is a 'green' delay composition that can compete with the burning rates offered by the Si/Pb 3 O 4 system.…”

“…The X-ray diffraction-de- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 termined combustion products appeared to be benign based on current regulations. Miklaszewski et al [114] concluded that Mn/MnO 2 appears to be a suitable low gas-producing, insensitive, less toxic delay composition with good longevity.…”

“…The differences were attributed to differences in the nature of the oxides present on the surfaces of the iron particles. Impact, friction, and electrostatic discharge tests have shown that the B 4 C/NaIO 4 /PTFE [4] and the Mn/MnO 2 [114] delay systems are insensitive to unintended ignition.…”