Double-base casting powder

Double-base and CMDB powders are loaded on shallow trays which are stacked in dry houses and subjected to a stream of hot air (140°F.) for several days. Results of a typical drying run for a double-base casting powder are shown in Figure 5. Initial drying is quite rapid however, extended cycles are required to get consistent values below the specification maximum, in this case 0.50% total volatiles (TV). 

Tensile Strength of Cast Double-Base Powder as a Function of Nitrocellulose Content P 423 Elongation of Cast Double-Base Powder as a Function of Nitrocellulose. Content. .. P 423 Modulus of Elasticity of Cast Double-Base Powder as a Function of 1 1 ... 

There is also an as-yet small but growing class of formulations known as PBX Plastic Bonded Explosive. PBXs are similar to rubber-base, composite rocket proplnts in that they consist of 85% or so of powdered high-energy explosive incorporated into a plastic matrix (which can be a conventional plastic or a double-base) and cast into place. 

Fig 2 Tensile strength of cast double-base powder as function of nitrocellulose content... 

Fluid Ball . Trademark of Olin Mathieson Chem Corp, Stamford, Conn 06904, for a pro-pint casting powder consisting of fully col-loided NC having an average particle diam of 50 microns or less. Compn can include liq solid modifiers. Used as binder constituent of modified double-base rocket propints Ref CondChemDict(1961), 503-R 504-L ... 

Another substantial increase in delivered energy was obtained by incorporating substantial amounts of solid oxidizer e.g., ammonium perchlorate) and metallic fuel e.g., aluminum) in the casting powder. The resulting family of composite-modified double-base (CMDB) propellants has found widespread use in ballistic missiles and space motors. 

Curing. The curing process of a double-base propellant converts a bed of casting powder granules whose interstices are filled with casting solvent to a macroscopically homogeneous mass of propellant. It is convenient to discuss the theory of curing on a microscale and on a macroscale separately. 

The dilatometric behavior of cast double-base propellant reveals much concerning the nature of the cure process. As an illustrative example, Figure 19 shows the curing behavior at constant temperature, 80°F., for a casting powder which has a porosity of about 2.7% based on the total propellant volume. 

When a plot of maximum total volume change vs. percent theoretical casting powder density is extrapolated to 100% of theoretical density, the total volume change is usually less than 0.1%. Thus, during cure of a double-base propellant, the volume change caused simply by mixing polymer and solvent is small. 

Nonpolymerizable, castable, gel-type (cast double base powder) ... 

The difficulty in the manufacture of large grains may be overcome by substituting the classical method for the extrusion of powder by a novel technique whereby cast charges of double base propellant are produced. 

Powder casting process. This is the most versatile process for manufacturing double base powder charges of any size and shape. 

According to Boynton and Schowengardt [54] the ultimate tensile strength of double base rocket charges should be 120 lb/in2 and elongation ca. 30%. The propellant which gives these properties contains less binder than the maximum imposed by the casting powder process, but it can be produced by the slurry process. 

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