Impact sensitivity of propellants

This paper reports an experimental study of the rapid deformation and ignition behaviour of a number of cast double-base propellants both at room temperature and at temperatures below the glass transition of those compositions that were elastomer modified. A range of techniques were used to obtain stress/strain data on the materials. A drop-weight machine with transparent anvils was used in conjunction with a high-speed camera to observe the deformation behaviour during impact. The aim was to gain understanding of the key parameters leading to the impact initiation of propellants. The only propellants that ignited violently in solid disc form at room temperature were the conventional compositions, the most sensitive being a composite modified propellant containing aluminium and ammonium perchlorate. All compositions were sensitized if they contained gas spaces. In addition, all the elastomer modified compositions were sensitized by cooling them below their glass transition (ca.210K). The mechanisms leading to ‘hot spot’ formation and ignition of the propellants are discussed.

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