Nitrocellulose hygroscopicity

Black Powder. Black powder is mainly used as an igniter for nitrocellulose gun propellant, and to some extent in safety blasting fuse, delay fuses, and in firecrackers. Potassium nitrate black powder (74 wt %, 15.6 wt % carbon, 10.4 wt % sulfur) is used for military appHcations. The slower-burning, less cosdy, and more hygroscopic sodium nitrate black powder (71.0 wt %, 16.5 wt % carbon, 12.5 wt % sulfur) is used industrially. The reaction products of black powder are complex (Table 12) and change with the conditions of initia tion, confinement, and density. The reported thermochemical and performance characteristics vary greatly and depend on the source of material, its physical form, and the method of determination. Typical values are Hsted in Table 13. 

Nitrocellulose powders gelatinized on the surface with centralite, camphor or nitro compounds are less hygroscopic since the layer of gel on the surface constitutes a non-hygroscopic coating which prevents the powder inside from attracting moisture. Nitrocellulose powders containing aromatic nitro compounds, e.g, dinitrotoluene (DNT) or dinitroxylene (DNX) are less hygroscopic. 

PETN differs from other nitric esters in failing to produce a colloid solution with nitrocellulose. This is the result of the symmetrical structure of PETN, which has a zero dipole moment. PETN is completely non-hygroscopic. Its specific gravity in crystalline form is 1.77. On compression the following density values are obtained ... 

Fig. 109. Hygroscopicity of nitrocellulose as a function of nitrogen content (de Pauw [119]).

The product is distinguished from nitrocellulose by its higher hygroscopicity and poorer solubility in organic solvents. Data illustrating the point are listed in Tables 102 and 103. 

Trinitronaphthalene appears to be a genuine stabilizer for nitrocellulose, a true inhibitor of its spontaneous decomposition. Marqueyrol found that a nitrocellulose powder containing 10 per cent of trinitronaphthalene is as stable as one which contains 2 per cent of diphenylamine. The trinitronaphthalene has the further effect of reducing both the hygroscopicity and the temperature of combustion of the powder. 

Dinitroglycerin gelatinizes collodion nitrocotton rapidly at ordinary temperature. The gel is sticky, less elastic, and more easily deformed than a nitroglycerin gel. Unlike the latter it is hygroscopic, and becomes softer and greasier from the absorption of moisture from the air. Water dissolves out the dinitroglycerin and leaves the nitrocellulose as a tough, stiff mass. 

Nitrostarch gives no color with iodine. It is insoluble in water and does not gelatinize to form a paste as starch does when it is boiled with water. It is not notably hygroscopic, but may take Up 1 or 2% of moisture from a damp atmosphere. It is soluble in acetone. The varieties of nitrostarch which are soluble in ether-alcohol contain about the same amounts of nitrogen as the varieties of nitrocellulose which dissolve in that mixed solvent. Nitrostarch does not form a good film or tough colloid as nitrocellulose does. 

Chromated Nitrocellulose(Coton-poudre chrome in Fr), Davey of England patented in 1877, the treatment of NC with a soln of chromate or dichromate together with or w/o K nitrate, glue or a hydrocarbon. This material was non-hygroscopic and suitable for use as a core in mining fuses, instead of BkPdr Refs l)Cundill(l889) in MP 5, 309 314 (1892) 2)Daniel(l902), 143 180... 

Glycerol dinitrate is a viscous liquid, but is more volatile and more soluble in water than nitroglycerine. It is hygroscopic and may be used as a gelatinizer of certain types of nitrocelluloses. It is more stable than glycerol trinitrate. Its vapors are toxic and cause headaches. 

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. 

DNAN forms colorless crystals with a melting point of 120 Celsius. It is fairly soluble in hot water, hot ethanol, methanol, and acetone. It is less soluble in cold water, cold ethanol, and insoluble in chloroform, benzene, ether, and petroleum ether. DNAN is somewhat hygroscopic, and moisture slowly decomposes it—should be stored in a desiccator. A small sample bums leaving a residue of carbon when ignited—a small sample can be detonated by the blow of a hammer. DNAN can be used in explosive compositions when alloyed with TNT, or other low melting secondary explosives, gun propellants with nitrocellulose, nitro starch, or nitroglycerine, and rocket propellants when mixed with ammonium perchlorate. DNAN also demonstrates usefulness for priming mixtures with lead azide, lead styphnate, or diazodinitrophenol, and for use in fireworks. ... 

NTA forms hygroscopic crystals or powder, which are soluble in water, acetone, isopropyl alcohol, and ether. It is used in blasting caps and detonators when mixed with RDX, making demolition charges when admixed with nitrocellulose or nitro starch, and in priming mixtures with lead styphnate, lead azide, or diazodinitrophenol. NTA is acidic and readily forms salts... 

Black powder is mainly used as an igniter for nitrocellulose gun propellants and to some extent in safety blasting fiises, delay fuses, and firecrackers. Potassium nitrate black powder (74 wt percent plus 15.6 wt percent carbon, 10.4 wt percent sulfur) is used for military applications. The slower-burning, less costly, and more hygroscopic sodium nitrate... 

This composition is somewhat hygroscopic because it contains strontium nitrate. When moistureproof stars are manufactured with this composition using nitrocellulose paste, they can be used in practice The burning rate is adjusted by changing the ratio of magnesium to oxidizers. Potassium perchlorate decreases the ash ... 

CoUoidaV lead azide. This is a pure fomi of lead azide (over 99% purity) in fine particles of 3-4 m. It is non-hygroscopic but not readily pourable and hence less adaptable for mass production. It is particularly sensitive to electric discharge and hence used for electric detonators. For tliis purpose colloidaf lead azide is often mixed wdth a concentrated nitrocellulose solution in ethyl ether-ethanol or oilier solvents. 

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