The Chemistry of Powder and Explosives - Sciencemadness Dot Org

BALL-GRAIN POWDER 329
in the presence of water than when water is absent. Diphenylamine
is dissolved in the ethyl acetate before the latter is added
to the water and nitrocellulose in the still. At the same time,
centralite or DNT or any other substance which it may be desired
to incorporate in the powder is also dissolved and added. The
water phase and the lacquer are then stirred for 30 minutes by
which operation the nitrocellulose is stabilized. 27 Starch or gum
arabic solution to secure the requisite colloidal behavior is then
introduced into the still, the still is closed, the temperature is
raised so that the lacquer becomes less viscous, and the mixture
FIGURE 82. Cross Section of Ball Grain, Double Base, Deterrent Coated
(112X). (Courtesy Western Cartridge Company.)
under pressure is agitated vigorously until the lacquer is broken
up into small globules of the correct size. The pressure is then
reduced, and the ethyl acetate is distilled off and recovered. If
the distillation is carried out too rapidly, the grains are shaped
like kernels of popcorn. If it is carried out at such a rate that the
volatile solvent is evaporated from the surface of the globules no
faster than it moves from the interior to the surface, if the distillation
is slow at first and more rapid afterwards, then smooth
ball grains are formed, dense and of homogeneous structure.
27 Diphenylamine in the presence of water thus has an action beyond
that which it has when it is added to the nitrocellulose gel (in the absence
of a separate water phase) during the manufacture of smokeless powder
by the usual process. Being preferentially adsorbed by the nitrocellulose, it
drives any acid which may be present out of the nitrocellulose and into
the water. After that it fulfils its usual function in the powder.