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Objective:
Currently, all small-caliber tracer and incendiary ammunition
is produced at the Lake City Army Ammunition Plant (LCAAP)
in Independence, Missouri. So that soldiers or marines can
select the correct ammunition while in combat or training,
the ammunition is made identifiable by applying low volatile
organic compound (VOC) paint to the projectile tip. The conventional
spray- or dip-paint application processes are sensitive to
several atmospheric factors, are inefficient and wasteful,
release toxic solvents, and cause environmental and occupational
health and safety hazards. As a substitute for traditional
paint application processes, this project investigated a powder
coating technology at the Concurrent Technologies Corporation
(CTC) test facility in Johnstown, Pennsylvania.
Technology
Description:
Powder
coatings are composed of finely ground plastic particles,
which consist of resins, pigments, fillers, binders and hardeners,
but no solvents. When exposed to heat, the plastic particles
melt or react and flow to form a continuous film of high durability
and chemical resistance. No toxic gases are emitted when powder
coatings are applied or cured. Powder coatings are typically
applied using electrostatic spray equipment and cured in an
oven. They can be either thermoplastic or thermoset.
Results:
At
the CTC test facility, 7.62-millimeter (mm) tracer projectiles
were loaded on a test jig, powder-coated with an epoxy-based
thermoset paint using a manual electrostatic spray gun, and
then cured in an oven. By performing standard Lot Acceptance
Tests, which included coating adhesion and finish quality,
and quick and easy visual identification of bullets, these
projectiles were compared with similar projectiles that had
been coated in a conventional painting process at LCAAP. The
powder coating was resilient and represented an improvement
over the conventional process. Both samples of projectiles
were subsequently loaded into cartridges at LAAP, and ballistics
tests were performed on the LAAP test range. The accuracy,
velocity and trace performance of each were indistinguishable.
Benefits
and Implications:
Powder
coatings can be stored indefinitely, have a lower curing time,
and are more easily removed from spray equipment as compared
to conventional liquid paints. The use of hazardous solvents
in the paint formulation would be eliminated, and the occupational
health of workers would improve. However, implementation on
the 7.62-mm cartridge line alone at LCAAP would not be economically
justifiable due to the currently low throughput rate. The
payback on the estimated $40,000 cost for the required facility
modifications would be 4-5 years unless the technology was
also implemented on other types of ammunition. Powder coating
is a versatile technology that is applicable to several calibers
of ammunition at LCAAP, and implementation for a wide range
of ammunition may be appropriate. Material (i.e., projectile)
handling methods however would have to be developed, and the
safety issues concerning the heat sources used to cure the
paints in the proximity of live ammunition would have to be
addressed. (Project Completed - 2003)
References:
1.
ESTCP
Cost and Performance Report. July 2003. (PDF File Format)
ESTCP Point of Contact:
Program Manager, Pollution Prevention
ESTCP Program Office
901 North Stuart Street, Suite 303
Arlington, VA 22203
Telephone: (703) 696-2128
Fax: (703) 696-2114
E-mail: P2@estcp.org
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