Binders and Other Accessory Materials

Compositions that are not used in loose powder form are consolidated in one of three ways They can be mixed with a sizable amount of a strong adhesive to form firm beads, bulbs, or elongated rods supported by wires, wood, or paper splints they can be compressed or loosely aggregated with the aid of adhesives to serve as overall burning stars or they may be pressed into a protective envelope with or without a binder. 

Though many mixtures compact quite well under compression, a certain amount of adhesive material is desirable in overall burning stars, be it that the rate of consolidation is slight, as is the case in many fireworks items, or that the pellet is subjected to strong adverse influences such as transportation vibration. 

In partially enclosed items, even though most of the mixture qiay be protected from physical disintegration by a strong cardboard or metal cylinder, binders are regularly added for increased strength and also for flame formation. The exception is the item whose proper function demands minimum gas development. 

Among water-soluble or water-dispersible binders are dextrins, gum arabic, casein, and animal hide glue. The latter has received great attention from the match manufacturers as well as from other industries. Hide glue is marketed in a great variety of viscosi- 

Fortunately, the less specialized formulations do not employ such a difficult malerial in fact, only rarely does one find a water-soluble colloid. A frequently found binder material is lacquer-grade nitrocellulose (MIL-N-244A, Grade D, sometimes also Grade A), dissolved in acetone (O-A-51) or other low-boiling solvents such as ethyl acetate. Celluloid (MIL-B-10854) solutions in acetone are sometimes preferred. Usual amounts are 1.8-4.0% on a dry basis. 

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