Revised Intumescent Coatings for the 60-mm PA124 Military Container

Report No. ARL-TR-3679
Authors: Pauline Smith and Kestutis Chesonis
Date/Pages: November 2005; 22 pages
Abstract: An intumescent coating has all the properties of ordinary paint; furthermore, this coating will not sustain combustion. Consequently, it will not burn, providing a high degree of protection to the subsurface. Upon exposure to flame or heat, it immediately foams and swells, contributing an effective insulation and heat shield for the subsurface. An intumescent coating system for fire and heat protection is specified for 60-mm mortar containers. The projected intumescent coating system for ammunition containers performed unsuccessfully during testing at the Aberdeen Test Center. The complexity of this project included paint delamination, cracking and chipping after the drop, and impactresistant test. The specified intumescent system (intumescent and topcoat) was supplied by NoFire Technologies Inc. and consists of a waterbased A-18NV, MIL-PRF-24596, type II intumescent paint and a solvent-based topcoat (Uracoat). The intumescent coating system is applied over the forest-green coating (basecoat) used on the containers. Testing performed on the NoFire intumescent coating system has shown it has poor flexibility, impact, and marginal moisture resistance. In order to improve intumescent coating system flexibility, a water-based emulsion topcoat was formulated by the U.S. Army Research Laboratory (ARL) to replace the Uracoat. The water-based emulsion topcoat when applied over the NoFire intumescent coating showed improved flexibility and impact resistance, but performed poorly in moisture resistance tests. Also, the same tests were performed on the NoFire intumescent with various Army coatings (i.e., MIL-DTL-64159 CARC topcoat, MIL-DTL-11195 Type II, ARL water-based emulsion topcoat) and showed similarly poor results as the Uracoat. As a result, it was concluded that the NoFire intumescent coating with any topcoat was designed for interior use, and an alternative intumescent coating system was pursued.
Distribution: Approved for public release
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Last Update / Reviewed: November 1, 2005