Nitroguanidine powders

For many years guanidine thiocyanate was the most easily prepared and the most commonly used of the salts of guanidine. Other salts were made from it by metathetical reactions. Nitro-guanidine, prepared from the thiocyanate by direct nitration with mixed acids, was found to contain traces of sulfur compounds which attacked nitrocellulose and affected the stability of smokeless powder, and this is one of the reasons why nitroguanidine powders did not come into early use. Guanidine thiocyanate is deliquescent. Strong solutions of it dissolve filter paper. 

The propellant which has exclusively been used for a long time in conventional military weapons is the smokeless (or, more accurately, low-smoke) powder. According to its composition, it can be classified as single-base powders (e.g., nitrocellulose powder), doublebase powders (e.g., nitroglycerine powder) and triple-base powders (e.g., nitrocellulose + nitroglycerine (or diglycol dinitrate) + nitroguanidine powders). 

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... 

The crystalline structure of 2-nitroguanidine had already been previously studied by Bryden and coworkers1 (Ref. 29 therein). They there report the existence, but not the position, of hydrogen bonds, which was instead rendered possible through the use of the neutron powder diffraction method5. The skeleton backbone of this molecule consisting of a central C atom and four N atoms is almost coplanar. Both nitramine groups are essentially on the plane of the molecular skeleton. 

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. 

Nitroguanidine Guanidine, Sulfuric acid, Water Secondary high explosive, Found in triple-base smokeless powders... 

Single base A smokeless powder that contains nitrocellulose, but does not contain nitroglycerin or nitroguanidine. 

Non-explosive substance (e.g. vaseline) are added to nitroglycerine powders to reduce the heat of explosion and the temperature of the flash. The addition of cool explosives such as nitroguanidine has the same effect. 

Investigations showed that the salts of other alkali metals are not so efficient in suppressing secondary flame as potassium salts. Fairly numerous experiments were carried out to clear up whether or not known antiknock substances, such as tetraethyl lead or nickel carbonyl prevent the development of a secondary flame. They proved to have no effect on its development. In practice, two methods for removing gun-flash may be employed, i.e. either a special flashless powder is produced, containing nitroguanidine or DNT and a small admixture of potassium sulphate,... 

Double base powders, i.e. nitroglycerine powders without a volatile solvent also include modem flashless powders containing nitroguanidine. 

Other patents of the interwar period include several that specified addition of substances rich in carbon, e.g. of powdered hydrocellulose, to obtain flashless charges. In the U.S.S.R. nitroglycerine powder was used in which a part of the nitroglycerine was replaced by aromatic nitro compounds. During World War II the most widely used flashless powder contained nitroguanidine (in Germany called Gudol powder). 

The idea of adding nitroguanidine to smokeless powder had been already considered by Vieille [45]. He suggested adding nitroguanidine to reduce the erosiveness of the powder (see p. 548)... 

It was difficult to manufacture since the nitroguanidine had to be introduced into the powder mass in a state of fine subdivision, otherwise the powder was not uniform. In some factories, therefore, methods were worked out to obtain nitroguanidine in the form of fine dust. 

Tubular powder without nitroguanidine for anti-aircraft and heavy guns [42]... 

Other substances suggested for flashless powder instead of nitroguanidine included aminotetrazole which was, however, rejected due to its hygroscopicity, and methylene-urea. 

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