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Making Ball Propellants

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Instead of falling into a tank after extrusion, the granules move immediately into a liquid-filled shaper that keeps the granules in constant motion. The action of granule against granule and against the walls and paddles of the shaper unit “beats” the cut granules into spheroids. The action is much like that of placing a cube of modeling clay into a large can, closing the lid, and shaking it. The clay cube will be rounded. The liquid in the shaper contains chemicals that start to draw off excess moisture from the granules. From the shaper, the granules move to a series of progressive evaporators that drive off unneeded solvents.

Although most finished ball powders are double-base, they start as pure nitrocellulose. In ball powder production, the nitroglycerin is added after shaping. The NG content is created by surface impregnation. The impregnated granules are sorted by size, and any coatings required are added before drying. If the powder is to be flattened ball, the granules are roller pressed at this still-soft stage.

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