A Compatibility Problem with the MK-148 Electric Delay Primer
Abstract
The MK-148 electric delay primer has a bridge-wire beaded with 2-4 mg of a mix containing approximately 90% normal lead styphnate (NLS) in a nitrocellulose binder cured by solvent evaporation. A ferrule or sleeve is potted (Scotchcast 8 epoxy resin) onto the bridge-wire plug. Additional epoxy resin is used to seal the bridge-wire ferrule to a stainless steel delay body containing, in sequence, an airgap, A-1A, delay mix, A-1A and lead azide. The Scotchcast 8 epoxy adhesive is an amine-cured resin. The amines, all low molecular weight and volatile, are major components of this adhesive and, as such, are specified by the U.S. Navy for use in this item--in spite of literature reports of incompatibility with explosives. This investigation was begun as a result of failure of some MK-148's for contract N60530-81C-0178 to fire after 28-day Temperature and Humidity (T&H) cycling between -65 and +160 F, with a cumulative exposure at the high temperature of approximately 384 hours. Microscopical study of pure unmilled normal lead styphnate (NLS) and milled NLS beads showed extensive chemical attack during exposure to the vapors of curing epoxy even at room temperature. NLS exposed to epoxy vapors for 16 hours 160 F was essentially destroyed, as shown by polarized light microscopy and x-ray diffraction. Amine-cured adhesives are incompatibile with lead styphnate; basic lead styphnate is more stable than NLS to amines but would still risk failure in units such as the MK-148. No amine-cured adhesives should be used in ordnance components requiring dependable performance of lead styphnate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 02, 1983
- Accession Number
- ADA203139
Entities
People
- T. G. Blake
- Walter C. Mccrone