Manufacture of Double-Base Propellants

Manufacture of Double-Base Propellants. The following methods are used a)Solvent Process -similar to that used for single-base proplnts,... 

Centralites are not only stabilizers, but gelatinizers as well. The latter property is taken advantage of in solvent-free manufacture of double base propellants. 

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. 

The application of nitrocellulose depends strongly on the degree of nitration. For example, guncotton with 13.45 percent nitrogen is used in the manufacture of double-base and high-energy propellants [4]. 

B) W.H. Rinkenbach, Calorific Values of Smokeless Powders as Affected by Variations in Composition, Granulation, etc , PATR 673 (1935) C) C.S. Davis, Development of Improved Propellant and Primer to Reduce Flash in Caliber. 50 Ammunition (Ignition Study) , PATR 1672 (1947) D) W.H. Rinkenbach, Study of Stability of Double-Base Propellants , PATR 1674 (1948) E) J.E. Rainier W.M. Rowe, Propellant for 2ES-40,000 Jato, T29 , PATR 1692 (1948) F) N.S. Garman et al, The Effect of Temperature Conditioning on Stability and Sensitivity Characteristics and the Chemical Composition of Ml and M6 Propellants Manufactured with Crude or Refined Dinitro-toluene , PATR 4841 (1975) (limited distrib)... 

Solventless Extrusion Process. The solvendess process for making double-base propellants has been used ia the United States primarily for the manufacture of rocket propellant grains having web thickness from ca 1.35 to 15 cm and for thin-sheet mortar (M8) propellant. The process offers such advantages as minimal dimensional changes after extmsion, the elimination of the drying process, and better long-term baUistic uniformity because there is no loss of volatile solvent. The composition and properties of typical double-base solvent extmded rocket and mortar propellant are Hsted ia Table... 

Paste. In double base propellant manufacture, the initial mixture of guncotton and nitroglycerine. 

Nitrocellulose is transported in tightly closed drums or in pasteboard drums lined with plastic bags inside, which contain at least 25% of a moisturizing agent (water, alcohol, isopropanol, butanol, etc.). Spherical NC particles are precipitated from solution under vigorous stirring, and preferably used for manufacturing of cast or composite double base propellants. 

Single base" smokeless powder, developed mainly in the United States, uses only nitrocellulose. "Double base" smokeless powder, developed in Europe, is a blend of nitrocellulose and nitroglycerine. "Cordite," a British development, consists of 65% NC, 30% NG, and 5% mineral jelly. The mineral jelly (a hydrocarbon material) functions as a coolant and produces substantial amounts of CO 2, CO, and H 2O gas to improve the propellant characteristics. "Triple base" smokeless powder, containing nitroguanidine as a third component with nitroglycerine and nitrocellulose is also manufactured. 

The Armed Forces demand a long shelf-life (min 10-12 years) for propellants for use in different rockets and missiles. However, the shelf-life of propellants is limited. There are some chemicals which on their addition to these propellants during their manufacture retard the processes responsible for their deterioration and consequently, increase their shelf-life. The main purpose of addition of these chemicals in propellant formulations is to enhance their shelf-life without adversely affecting their manufacturing processes and properties. Such chemicals or additives are known as stabilizers in case of DB and composite modified double-base (CMDB) propellants whereas anti-oxidants in the case of composite propellants. The additives for this purpose are therefore selected depending on the type of propellant. 

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