Nitrocellulose stabilization

Single-base casting powder the casting powder consists of nitrocellulose, stabilizer, solid additives for ballistic modification, and a small amount of plasticizer. The normal ratio of casting powder to casting solvent, 2 1 by volume, yields a final composition of approximately 60% nitrocellulose. 

Later experiments were carried out with a nitrocellulose stabilization process that consisted in treating a partially purified nitrocotton in an ammonia bath (e.g. Reeves and Giddens [12]). This was based on the supposition that ammonia was capable of neutralizing accurately adds contained in the interior of nitrocellulose fibres. However, this method has not been adopted in practice, since it was feared that the sulpho groups attached to cellulose in the form of mixed esters would undergo only partial hydrolysis in the presence of ammonia and later spontaneous hydrolysis of these substituents in the finished (stabilized) product might reduce its stability. 

Procedure 13-02D Preparation of average nitrogen content (11 to12%l Nitrocellulose (stabilized form)... 

A filter cake from the wringer is washed to remove absorbed acid, transferred to a slurry tank of water, and quickly submerged, after which the nitrocellulose is pumped to the stabilization operation as a diluted water slurry. Exhaust systems are installed to protect personnel and equipment from acid fumes, and water sprays and cyclone separators are used for acid fume recovery before venting to the air. 

The beater additive process starts with a very dilute aqueous slurry of fibrous nitrocellulose, kraft process woodpulp, and a stabilizer such as diphenylamine in a felting tank. A solution of resin such as poly(vinyl acetate) is added to the slurry of these components. The next step, felting, involves use of a fine metal screen in the shape of the inner dimensions of the final molded part. The screen is lowered into the slurry. A vacuum is appHed which causes the fibrous materials to be deposited on the form. The form is pulled out after a required thickness of felt is deposited, and the wet, low density felt removed from the form. The felt is then molded in a matched metal mold by the appHcation of heat and pressure which serves to remove moisture, set the resin, and press the fibers into near final shape (180—182). 

Most of over six million dentures produced annually in the USA are made of acrylics (PMMAs) that includes full dentures, partial dentures, teeth, denture reliners, fillings and miscellaneous uses. Plastics have been edging into the dental market for over a half century. Even before the introduction of acrylics to the dental profession in 1937, nitrocellulose, phenol-formaldehyde and vinyl plastics were used as denture base materials. Results, however, were not wholly satisfactory because these plastics did not have the proper requisites of dental plastics. Since then, PMMAs have kept their lead as the most useful dental plastics, although many new plastics have appeared and are still being tested. Predominance of PMMAs is not surprising, for they are reasonably strong, have exceptional optical properties, low water absorption and solubility, and excellent dimensional stability. Most denture base materials, therefore, contain PMMA as the main ingredient. 

Mittasch Stability Test for Nitrocellulose. A test based on the measurement of press developed on decompn of NC. The app may be considered a very complicated modification of devices originated by Abel (Ref 4, p 241) and Hess (Refs 1 4). Abel heated NC samples in vac and detd the press increase. Hess believed that on heating NC in a closed vessel contg air, connected to a Hg manometer, it would be possible to achieve conditions more closely resembling those in storage in closed magazines. Neither of these methods found any practical application... 

S. Helf, Use of Saline Leaches to Stabilize Nitrocellulose , PATR 2550 (1958) 9) E.M. Smolin... 

Although these are no longer used as explosives, they are formed from diphenylamine that is used as a stabilizer for nitrocellulose explosives. The metabolism of nitrodiphenylamines has been examined under anaerobic conditions, and phenazine and 4-aminoacridine that are cyclization products of the initially formed 2-aminodiphenylamine have been identified (Drzyzga et al. 1996). 

RCF itself is not a good barrier, nor can it be heat-sealed. Barrier and heat-sealing are conferred by coatings of nitrocellulose or polyvinylidene chloride on one or both sides. RCF has poor dimensional stability due to moisture loss or gain. Its principal use is in laminates and over wrapping. 

The nature of the nitrocellulose used is of particular importance in explosives if freedom from exudation of free nitroglycerine during storage is to be avoided. Nitroglycerine is only a poor solvent for nitrocellulose and stability of the gel depends on continuous formation and breakdown of gelled structures. The distribution of nitrogen content and viscosity, even in the individual fibres of the nitrocellulose, is therefore of paramount importance. 

For nitrocellulose, including guncotton, the most suitable stability test is the B and J (Bergmann and Junk) test in which 2 g dried material is heated for 2 h at 132°C, the gases evolved being dissolved in water. The nitric acid in this water is reduced to nitric oxide, which is measured by volume. 

Many methods have been proposed and are used to study the thermal stability of propellants and to ensure the absence of possible autocatalysed decompositions during storage. None are sufficiently reliable to merit individual description. In practice, stabilisers are added, the usual being diphenylamine for nitrocellulose powders and symmetrical diethyl diphenyl urea (carbamate or centralite) for double base propellants. Provided a reasonable proportion of stabiliser remains, the propellant can be assumed to be free from the possibility of autocatalytic decomposition. The best test of stability is therefore a chemical determination of the stabiliser present. 

Butantriol wird mit Salpetersaure/Schwefelsaure nitriert. Die Stability des nitrierten Produktes ist sehr gut. Die Gelatinierung mit Nitrocellulose ist ahnlich der des Nitroglyzerins. 

Es ist unloslich in Wasser, loslich in Aceton und Toluol. Trinitrophenyl-glykolethernitrat ist sehr stabil und gelatiniert Nitrocellulose in der Warme. 

M55 rockets pose the greatest storage risk because they contain approximately 20 pounds of M28 propellant, a double-base propellant composed of nitroglycerine, nitrocellulose, plasticizers, a bum-rate modifier, and a stabilizer. The exact composition is given in Table 1-4. The propellant slowly decomposes exother-... 

Uses Solvent for lacquers, varnishes, dopes, nitrocellulose, natural and synthetic resins in cleaning solutions, varnish removers, dye baths mutual solvent for formation of soluble oils lacquer thinners emulsion stabilizer anti-icing additive for aviation fuels. 

Uses Camphor substitute in celluloid impregnating roofing paper plasticizer in lacquers and varnishes renders acetylcellulose, airplane dope, nitrocellulose, stable and fireproof gasoline additives insecticides floatation agents antioxidants, stabilizers, and surfactants. 

Uses. Rubber antioxidant and accelerator fungicide in veterinary medicine stabilizer for nitrocellulose explosives and celluloids manufacture of dyes... 

---