Stabilization nitrostarch

One of the nitrostarch stabilization methods worked out by Hackel and T. Ur-banski (unpublished) consisted in giving the nitrostarch a very finely divided form so as to make it possible for water to invade the interior of the nitrostarch granules. It is, in fact, a method very similar in principle to the process of stabilizing nitrocellulose, since the fundamental operation in the latter consists in cutting the nitrocotton fibres into shorter pieces so as to open the interior of the fibres and permit water to penetrate. 

Experimenting with a still stronger nitric add, sp. gr. 1.52, Will and Lenze [1] prepared nitrostarch characterized by a nitrogen content of 14.04%. They established that it is possible to produce nitrostarch of high nitrogen percentage and adequate stability providing it is subjected to a stabilization boil in ethyl alcohol. 

Initially nitrostarch could not be used in practice due to its inadequate chemical stability, but by the beginning of the present century nitrostarch had found practical application in the U.S.A., where it was introduced by a British chemist, Hugh [24] who in 1900 and 1903 constructed and set in operation two nitrostarch factories one near Asburg Park, New Jersey, and the other near Wharton. Hugh advertized non-freezing Hugh s Powder as a substitute for dynamite. It has been proved to be pure nitrostarch. 

In the period after World War I the efforts of the Trojan Powder Co. to improve the chemical stability of nitrostarch were continued, and a series of patents was granted (Waller [28]). 

Special care was devoted to the manufacture, stabilization and application of nitrostarch in the Trojan Powder Co. under the direction of Snelling. His work during the period from 1918 to 1945 is embodied in a large number of patents [29]. 

In principle the viscosity of nitrostarch is affected by the same factors which cause a change of viscosity in nitrocellulose. Thus a high nitrogen content in the product, an elevated nitration temperature, or an intensive stabilization boiling of the nitrated product lowers the viscosity of the nitrated substance. However, in the case of nitrostarch the changes in viscosity under the influence of these factors are insignificant. 

The problem of how to stabilize nitrostarch has been solved by different means, but the majority of stabilization processes remain obscure as patent secrets. None the less, from certain observation some general conclusions can be made. It was early observed by Bechamp [13] that nitrostarch obtained by nitration in nitric acid alone is more stable than one obtained by means of nitric acid mixed with sulphuric acid. This has been confirmed experimentally by Hackel and T. Urbanski [18], and seems likely to be explained by the formation of starch sulphates or mixed nitric and sulphuric esters of starch. 

The other principal operation in the stabilization of nitrostarch is prolonged boiling, initially in acid water, and finally in alkaline water. As in the stabilization of nitrocellulose premature alkalization of the stabilizing medium is not recommended as this hinders the hydrolysis of sulphuric esters. Nevertheless in some American contributions (as mentioned above) early addition of ammonia for washing nitrostarch is reported to favour the formation of a stable product. 

For laboratory purposes nitrostarch may be stabilized by boiling with ethyl alcohol. The insoluble part containing 13.4-13.9% N is characterized by considerably higher chemical stability than the raw product before boiling (Ashford, Cook and Hibbert [39]). 

Schuckher also patented (1890) a method for the prepn of Nitrostarch which consisted of dissolving dried and pulverized starch in nitric acid, and pouring the soln into mixed nitric-sulfuric acid. After washing and drying, the Nitrostarch was stabilized by the addition of aniline... 

Trojan Explosive. A Nitrostarch based expl used by the USA during WWI and to a limited extent in WWII in demolition charges. It contained Nitrostarch 40, Na nitrate 37.7, Ba nitrate 20, oil 0.8, and stabilizer (diphenylamine or Ca carbonate) 1.5% grey solid pressed in Vi and 1-lb... 

Nitrostarch resembles nitrocellulose in several respects, but, owing to its poor stability, difficulty in preparation and hygroscopicity, it is not used anywhere outside the USA. Fleadache-free industrial explosives are based on nitrostarch. 

Heat tests at 120° and 134.5°C indicate nitrostarch is less stable than nitrocellulose at ordinary temperatures, the two appear to be of similar stability as judged by long term storage tests. 

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