Nitrocellulose types

The nitrocellulose coated films were the only type available until the early 1950 s, when vinylidene chloride copolymer coatings were introduced. The method of coating is essentially the same as that used for the nitrocellulose type. This later type of coating has the advantage that subsequent conversion, eg printing and bag making, does not have as marked an effect on barrier properties as on the nitrocellulose coatings where the water vapour permeability can be increased quite appreciably. 

The two procedures primarily used for continuous nitration are the semicontinuous method developed by Bofors-Nobel Chematur of Sweden and the continuous method of Hercules Powder Co. in the United States. The latter process, which uses a multiple cascade system for nitration and a continuous wringing operation, increases safety, reduces the personnel involved, provides a substantial reduction in pollutants, and increases the uniformity of the product. The cellulose is automatically and continuously fed into the first of a series of pots at a controlled rate. It falls into the slurry of acid and nitrocellulose and is submerged immediately by a turbine-type agitator. The acid is deflvered to the pots from tanks at a rate controlled by appropriate instmmentation based on the desired acid to cellulose ratio. The slurry flows successively by gravity from the first to the last of the nitration vessels through under- and overflow weirs to ensure adequate retention time during nitration. The overflow from the last pot is fully nitrated cellulose. 

Ink Types. There are 10 gravure ink types categorized by the binders or solvents used A, aUphatic hydrocarbon B, aromatic hydrocarbon C, nitrocellulose D, polyamide resins E, SS nitrocellulose M, polystyrene T, chlorinated mbber V, vinyls W, water-based and X, miscellaneous. 

For example, Day-Glo HM Series toners come ia a range of colors suitable for flexographic and gravure inks of the solvent-base type. The Radiant GF Series and Lawter HVT Series are also suitable for this type of apphcation (see Table 2). Generally, these toners are of the formaldehyde—sulfonamide type and requite oxygenated solvents, primarily alcohol—ester blends, for proper solution. For appHcations such as flexographic printing on film, these materials are modified with other resias such as nitrocellulose or polyamides ia the finished ink. 

Two of these types are lacquers, giving quick drying to the dust-free state at ambient temperature, but at the expense of lower film build. Nitrocellulose-based lacquers are preferred in some European countries and acrylic lacquers in North America. Nitrocellulose is plasticised with nondrying alkyds, polyester and liquid plasticiser. Acrylics are plasticised internally by use of plasticising monomers with methyl methacrylate and by solvent plasticiser. Acrylics give better durability and nitrocellulose gives easier application. 

Cellophane is an old and respected packaging material which has been improved over the years. The two general types are coated with nitrocellulose (N/C) and polyvinylidene chloride (PVDC), respectively. Nitrocellulose-coated cellophane is moisture proof and useful for packaging dry products. It does not exclude oxygen or moisture completely, but for noncritical products it is entirely satisfactory. Baked goods are often packaged in this breathing type film. It is often used for cookies, candies, and rolls because its lack of taste and odor makes it very compatible with these products. 

Shortly afterwards (1885) Vieille s powder was introduced in France under the name of B powder (Poudre B). Vieille utilized two types of nitrocellulose for its manufacture collodion cotton CP2, soluble in a mixture of ether and alcohol and forming the powder dough cotton CPi, insoluble in a mixture of ether and alcohol, incorporated into the powder mass in the form of unchanged fibres... 

A third type of propellant, the composite modified-double-base propellant, represents a combination of the other two types. These propellants are made from mixtures of nitroglycerine and nitrocellulose or similar materials, but with crystalline oxidizers such as ammonium perchlorate also included in the matrix. 

Figure 3. E. chrysanthemi cell surface labelling with sulfo-NHS-biotin. After labelling, the proteins were separated by SDS-PAGE, blotted onto nitrocellulose and revealed with PemB-antibodies (A) or with streptavidin-peroxidasc (B). Lane 1 A350 (wild type) lane 2 A837 kdgRy, lane 3 A350/pPME6. An arrowhead indicates the PemB position.

Nitrocellulose is usually handled wet and containing approximately 30% of water. Under these conditions it can be considered as a nonexplosive material when the nitrogen content does not exceed 12-6%. More highly nitrated cellulose is known as guncotton and is explosive even when moderately wet. When dry, nitrocellulose of all types is an extremely sensitive and dangerous explosive. Dry nitrocellulose is required for use in certain types of explosives and is then prepared by slow drying of the wet material in a current of warm air. 

Zapon. The fusehead is finally given a coat of a nitrocellulose solution as a protective layer and this coat may well be coloured with pigment so that the type of fusehead can readily be identified. 

The incorporating process is carried out in mixing machines of the Werner Pfleiderer type, that is with two heavy horizontal blades in a specially shaped bowl. Incorporation consists of mixing the alcohol wet nitrocellulose and other ingredients with a solvent, normally ether and alcohol mixture. The amount of solvent used is adjusted so that the final consistency is that of a stiff dough. 

Solvent type propellant. A double base propellant in which solvent is used to assist the gelatinisation of the nitrocellulose. 

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