Viscosity of nitrocellulose

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. 

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. 

The viscosity of nitrocellulose solutions in ether-alcohol undergoes similar changes as the composition of the solvent is modified. 

Fig. 102. Influence of the composition of the solvent (alcohol and ether) on the viscosity of nitrocellulose solutions (Gibson and McCall [57]).

Fig. 103. Change of viscosity of nitrocellulose solution in amyl acetate with addition of aromatic hydrocarbons, according to Drinbcrg [62].

The effect of temperature on the viscosity of nitrocellulose solutions has been studied by many authors, e.g. Nishida [68], Drinberg [62], E. Karrer et al. [69], Kozlov [70] and Goldman [71]. These experiments showed that the viscosity of concentrated nitrocellulose solutions is lowered more quickly, the higher the concentration of the solution. Attempts were made by E. Karrer, Berl and Umstatter [69] to find a formula expressing the relationship between the viscosity and the temperature (from 20 to 48°C). Shor [72] has examined the viscosity of nitrocellulose solutions within the concentrations range 14.9-17.9% and at temperatures from 0 to 40°C. On the basis of a mathematical analysis of the numerical results, the author has deduced the following formula ... 

Fig. 104. Change of viscosity of nitrocellulose solution with temperature (o —experimental and h— calculated values), according to Shor...

The relationship between the viscosity of nitrocellulose solutions and the age of poplar wood cellulose according to Pascal [74], is shown in Table 45. 

The effect of heat treatment of cellulose on the viscosity of nitrocellulose solutions... 

Effect of the conditions of nitration. The conditions under which the nitration was carried out exert an appreciable influence on the viscosity of nitrocellulose solutions. Thus a high nitrating temperature produces low viscosity nitrocellulose... 

The relationship between the nitrogen content and viscosity of nitrocellulose... 

In order to avoid the degradation of cellulose Wannow [82] used a mixture of nitric add with phosphoric add and water at temperatures of 0 and 20°C. The constant degree of polymerization was demonstrated by measuring the osmotic pressure. It has been confirmed that the viscosity of nitrocellulose solutions depends upon the nitrogen content of the substance (Fig. 105). 

Fig. 105. Change of viscosity of nitrocellulose solutions with nitrogen content (Wannow [82]). h— Nitration at 0PC, o — at 20°C.

A particularly marked change in the viscosity of nitrocellulose results from keeping it boiling in solutions of different reagents — bases and acids. In order to lower the viscosity of nitrocellulose, careful boiling in an alkaline medium is sometimes applied in practice. 

The viscosity of nitrocellulose is also affected by prolonged exposure to sunshine primarily by ultra-violet rays. It is beyond question that these cause shortening of the molecular chain. (Donald [87], Fric [88], Breguet and Caille [89], Stark [78] and others). 

Ultrasonic waves also bring about a reduction in the viscosity of nitrocellulose. The effect is more marked the higher the initial viscosity, and thus the longer the nitrocellulose chains (Sollner [93] Schmidt and Rommel [94]). For instance, nitrocellulose with a molecular weight of 123,000, estimated by means of Staudinger s viscosity equation, subjected in solution form to the action of ultrasonic waves suffered a degradation to a molecular weight of 70,000-80,000. 

Sometimes an increase in the viscosity of nitrocellulose is possible, through cross links formed between free hydroxyl groups. This involves the chemical reactions of cellulose, which are discussed later (see p. 303). 

It follows from the experiments of Nishida [98] and Kozlov [70] that mixing or stirring solutions of nitrocellulose causes the viscosity to increase initially and then to fall. As mentioned already (p. 261) the viscosity of nitrocellulose is of major... 

There exist instances where an increase in the viscosity of nitrocellulose solutions is recommended as in the product intended for manufacture of blasting gelatine, i.e. for the solution of nitrocellulose nitroglycerine. The solution must have the consistency of firm gelatine. 

Radiation of 253.6 mft wave-length especially is capable of reducing the viscosity of nitrocellulose solutions. Radiation of 366 mfi wave-length has practically no influence on the viscosity. Nitrogen content was decreased in both cases. With 366 mp, radiation applied under specific experimental conditions, the nitrogen content was reduced after 48 hr from 11.85 to 11.68%. 

The viscosity of nitrocellulose is also reduced. For instance, during 2 hr kiering nitrocellulose with a polymerization degree P of 200 undergoes a de-polymerization to P = 50, at the same time losing 0.12% of nitrogen. 

Stabilization. After being thoroughly washed free from acid, the nitrocellulose is subjected to stabilization-either in boilers and afterwards in autoclaves (Fig. 153), or directly in autoclaves. Pressure boiling nitrocellulose in autoclaves makes it possible to control the viscosity of nitrocellulose with a high accuracy, since both time and temperature are controlled. The kiers for lacquer nitrocellulose manufacture are... 

Vibrometer 366 Vieille Test 179 366 Virial equation 120 viscosity of nitrocellulose 224 Visol Visol-1 -4 -6 = vinylethylether and mixtures with isopropylalcohol and vinylbutylether liquid rocket fuel (german)... 

Both these characteristics are responsible for the veiy high viscosity of nitrocellulose solutions. 

The EFFECT OF HEAT TREATMENT OF CELLULOSE ON THE VISCOSITY OF NITROCELLULOSE SOLUTIONS... 

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