Cuprammonium fluidity, cotton cellulose

Figure 9. Data showing the change in cuprammonium fluidity of cotton cellulose in acids at 20 °C. (Reproduced with permission from Ref. 26.

The rate of breakage of cellulose bonds in cotton is readily found from the changes in the degree of polymerization (DP) as exposure continues, using the cuprammonium fluidity as a measure of the DP. In jute, however, this method is not always satisfactory because it is difficult to achieve a complete dissolution of the cellulose component in cuprammonium hydroxide because of interference from the lignin in the fiber. Moreover, preliminary removal of lignin is not advisable, as whatever the process used, it is always liable to cause some degradation of the cellulose. 

Among the various solvents suggested for dissolution of cellulose, cuprammonium solution is recommended as a general solvent having 15 0.1 g/1 Cu, 200 5 g/1 NHj and less than 0.5 g/1 nitrous oxide. The fluidity in this solvent of the solution of cotton is given by... 

A 0-5 per cent solution of a regenerated cellulose has a fluidity of about 40, which is approaching the limit of accuracy of measurement. It is therefore usual to work with a 2 per cent solution which brings fluidities into the range of 7-5 to 35,- and normally well-bleached regenerated cellulose rayon should have a fluidity of 11 to 12. For mixtures of cotton and viscose or other chemically similar rayons, the weights of fibre required per 100 ml of cuprammonium solution are given in Table 3.2. 

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