R. Meyer J. Köhler A. Homburg Explosives

Gunpowder
156
lose mixture is gelatinized with the aid of solvents – mostly alcohol and
ether. Additives – stabilizers in particular – can be incorporated at this
stage. The plastic solvent-wet mass thus obtained is now shaped in
extrusion presses to give strips or tubes and is cut to the desired
length by a cutting machine. The residual solvents in the powder are
removed by soaking the powder in water and drying. The dried powder
is then polished in drums and is graphitized. A surface treatment is
performed at the same time, using alcoholic solutions of Centralite,
dibutyl phthalate, camphor, dinitrotoluene, or other phlegmatization
agents.
To make nitroglycerine powder, nitrocellulose is suspended in water,
the suspension is vigorously stirred, and nitroglycerine is slowly introduced
into the suspension, when practically all of it is absorbed by
the nitrocellulose. The bulk of the water (residual water content
25–35%) is then centrifuged off or squeezed out, and the powder
paste is ground. It is then mixed by mechanical kneading with nitroglycerine-insoluble
additives and is gelatinized on hot rollers, as a
result of which the water evaporates, leaving behind a residual water
content of about 1%.
This product, which is thermoplastic, can now be geometrically
shaped as desired, in accordance with the type of the powder, using
finishing rollers, cutting and punching machines, or hydraulic extrusion
presses.
This solventless processing avoids variations in the characteristics of
the products due to the presence of residual solvents. No prolonged
drying operations are needed for ballistic stability of the gunpowder.
If the use of solvents is required in the production process of double
and triple base propellants, the nitroglycerine can be introduced in the
mixtures in the form of a “master mix”, a gelatinized mixture consisting
of 85% nitroglycerine and 15% alcohol-wet nitrocellulose of the same
type as the prescribed powder component.
Depending on their intended use, nitroglycerine powders have a nitroglycerine
content between 25 and 50%.
In the USA and in the United Kingdom, a large amount of nitroglycerine
and nitroguanidine powders are still produced with the aid of
solvents. Acetone is added to nitroglycerine in order to facilitate the
kneading and pressing operations, but must be subsequently removed
by drying.
A number of liquid nitrate esters other than nitrocellulose have been
recently used, including diglycol dinitrate, metriol trinitrate, and butanetriol
trinitrate, of which diglycol dinitrate has been the most extensively
employed. Powders prepared with it or with triglycol dinitrate are lower
in calories. This fact is relevant to the service life of the gunbarrels in