Nitrocellulose viscosity

Concentration of n2o4% Nitrogen content of nitrocellulose % Viscosity of a 2% solution in acetone Stability min... 

Conventional nitrocellulose lacquer finishing leads to the emission of large quantities of solvents into the atmosphere. An ingeneous approach to reducing VOC emissions is the use of supercritical carbon dioxide as a component of the solvent mixture (172). The critical temperature and pressure of CO2 are 31.3°C and 7.4 MPa (72.9 atm), respectively. Below that temperature and above that pressure, CO2 is a supercritical fluid. It has been found that under these conditions, the solvency properties of CO2 ate similar to aromatic hydrocarbons (see Supercritical fluids). The coating is shipped in a concentrated form, then metered with supercritical CO2 into a proportioning airless spray gun system in such a ratio as to reduce the viscosity to the level needed for proper atomization. VOC emission reductions of 50% or more are projected. 

Nobel invented gelatinous dynamite in 1875 by accident. He investigated the effect of nitroglycerine on the collodion (nitrocellulose in a mixture of ether and alcohol) that he used to treat a cut finger and found that it produced a tough plastic material with adjustable viscosity and high water resistance. 

Nitrocellulose is always in motion in the digester and well suspended in water, so that each fiber receives uniform treatment, producing a uniform viscosity much superior to the batch product. The continuous product has no oppor-... 

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. 

When a major portion of Guncotton was dispersed with acetone-alcohol and the residual portion with one of the above compds, equal weights of the compds were superior to dibutyl phthalate and to triacetin first, with respect to time reqd for complete dispersion and secondly, in producing solns of low viscosity Ref A.J. Philips, The Relation of the Hydrogen Bonding Concept to the Gelatinization of Nitrocellulose, PATR 1249 (March 1943)... 

Fedoroff, "Basic Research Leading to the Development of Ideal Propellants. Preparation of Low Viscosity, High Nitrogen Nitrocellulose , PATR 1678 (Feb 1948)... 

Energetic Plashcizer or co-plashcizer for high viscosity nitrocellulose (NC) and most preferred plashcizer for cyclodextrin nitrate polymers... 

With wood nitrocellulose smaller amounts of solvent are used (70-90%). This is accounted for by the lower degree of polymerization of wood cellulose in comparison with that of cotton. With its lower degree of polymerization wood nitrocellulose swells and dissolves more readily, producing solutions of a relatively low viscosity. 

The final web thickness of flake and tubular powders, after the removal of solvent, amounts to 53-65% of the web thickness of the strip at the moment of extrusion. The extent of shrinkage depends on such factors as total solubility, the viscosity of nitrocellulose, the quantity of solvent and the composition of the dough at the moment of extrusion. A greater solubility and a higher content of solvent lead to greater shrinkage of the strip. 

An important factor influencing the dimensions of the predried powder is the viscosity of the nitrocellulose solution. The lower the viscosity of the nitrocellulose, the greater is the shrinkage of the nitrocellulose gel on drying. This produces flakes or tubes of considerably smaller size than those from nitrocellulose of higher viscosity. 

Finely ground nitrocellulose of low viscosity was used. It was impregnated with DGDN under water in the usual way. After dehydration in a centrifuge to a moisture content of 18-22%, the blend was stirred into molten TNT. The vat was evacuated to evaporate the water and to produce a homogeneously gelatinized grain. 

A highly concentrated dispersion of carbon black is first prepared with a portion of the binder and solvent. The viscosity of this concentrate is a function of the particle size, structure, and surface chemistry of the black, the type of binder and its interaction with the pigment black, and the proportions of black, binder, and solvent. The final paint is made from the concentrate by adding more binder and solvent, its carbon black concentration is 3-8% referred to the solids content. Wetting agents are sometimes added to improve dispersibility and prevent flocculation. A number of concentrates for paint manufacture e.g., carbon black-nitrocellulose chips or carbon black -alkyd resin pastes, can be obtained from paint producers. 

Polymerization degree of nitrocellulose (determined by measuring the viscosity of acetone) 77 170 220 440 670 1360 2500... 

Water content of nitrating acid % Nitrogen content of nitrocellulose /o Solubility % Molecular weight of nitrocellulose (from viscosity measurements)... 

With solutions that have been prepared from solvents at a limiting ratio, i.e. where a small change in the proportion of the solvents may cause the dissolved nitrocellulose to coagulate, the highest viscosities are observed. The question is discussed below. 

Viscosity, as well as solubility, is a most important characteristic for distinguishing various types of nitrocellulose. The determination of viscosity is of great theoretical importance, since it is used to study the degree of polymerization of nitrocellulose. In commercial practice viscosity frequently plays a decisive part, for it is used to assess suitability of nitrocellulose for specific purposes. Thus, in... 

With regard to their viscosity, nitrocellulose solutions demonstrate the typical properties of lyophilic colloids. The action of pressure, temperature and concentration causes anomalies to appear indicating that these solutions deviate from the... 

Fig. 101. Change of viscosity with addition of water to solutions of nitrocellulose in acetone (Masson and McCall [58]).

The viscosity of nitrocellulose solutions is to some extent dependent on the composition of the solvent, and on its solvent capacity or strength . Masson and McCall [58] have examined the viscosity of nitrocellulose solutions in acetone to which different amounts of water had been added. They obtained a curve, reproduced in Fig. 101, that illustrates the effect of the water content of the acetone on the viscosity of nitrocellulose solutions. 

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