Erosiveness nitroguanidine

Ordnance propellants are required to give the minimum of muzzle flash, smoke and barrel erosion. All these objectives are assisted by adding to the propellant a proportion of nitroguanidine (picrite), made by treating guanidine nitrate with sulphuric acid and brought to very fine particle size by recrystallisation and disintegration. 

Attention has been paid to nitroguanidine as an explosive since Vieille [28] found that the gases from the decomposition of nitroguanidine are less erosive than those from the decomposition of other explosives of comparable power (Table 4). 

Vieille expressed the opinion that nitroguanidine is less erosive than other explosives of the same power due to its low temperature of explosion. On the basis of experiments with a manometric bomb Patart [55] calculated the following data for nitroguanidine as an explosive ... 

Vieille considered that erosion is caused by fusion of the metal and subsequent expulsion of the molten substance. The results of Vieille s experiments are summarized in Table 170. The weak erosive action of nitroguanidine, attributable to its low temperature of explosion, is noteworthy. 

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)... 

An experiment with 18.11 grams nitroguanidine in a bomb of 75.0 cc. capacity (density of loading 0.241) showed an erosion of 2.29 per gram of explosive. 

Nitroguanidine (NQ) was first prepared by Jousselin in 1887 (Fig. 1.3). However, during WWI and WWII it only found limited use, for example in formulations with AN in grenades for mortars. In more recent days NQ has been used as a component in triple-base propellants together with NC and NG. One advantage of the triple-base propellants is that unlike double-base propellants the muzzle flash is reduced. The introduction of about 50 % of NQ to a propellant composition also results in a reduction of the combustion temperature and consequently reduced erosion and increased lifetime of the gun. NQ can be prepared from dicyandiamide and ammonium nitrate via guanidinium nitrate which is dehydrated with sulfuric acid under the formation of NQ ... 

Ref 26, p 387) that the gases from the expIns of NGu (Nitroguanidine) were much less erosive than chose from other expls of comparable force, and considered this fact to be in harmony with his general conclusion chat the hotter expls are the more erosive. In his experiments the explns were made to take place in a steel bomb, 17.8cc capacity, equipped with a crusher gauge and with removable perforated, steel plug thru the perforation in which the hot gases from the expln were allowed to escape. They swept away, or eroded off, a certain amt of the metal. 

Because of the low temperature of explosion, about 2,098°C, nitroguanidine is used in triple-base propellants that are practically flashless and less erosive than nitrocellulose-nitroglycerin propellant of comparable force. When used by the Germans in World War II in antiaircraft guns, a nitroguanidine propellant increased the barrel life from 1,700 firings to about 15,000 firings. 

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