Alkali solubility
The methods CCA8 : 53 and Merkblatt IV/29 were investigated in detail as reported before, but at present the industry of Japan has no positive intention of adopting CCA8 : 55 or Merkblatt IV/29B/55 or any other similar methods as the standard.The Committee of Japan, however, is not indifferent about these methods, for alkali solubility tests continue to excite the attention of several research laboratories.
CED or CAM
The dissolving power of both the solvents and the stability of cellulose against depolymerization in them were measured.When the two-stage dissolving procedure is used, cupriethylenediamine has a greater dissolving power than cuprammonium for samples of cellulose having medium degree of polymerization.It was observed that cellulose is far more stable in cupriethylenediamine than in cuprammonium.These tests were done at such concentrations that the product of intrinsic viscosity and concentration equaled three.
Flow behaviors of cellulose solutions
To secure some scientific background which might be helpful to authenticate or revise the methods for viscosity determination, the flow curves of solutions of cellulose varying in degree of polymerization in cupriethylenediamine and in cuprammonium were investigated.A capillary viscometer with continuously varying pressure head as designed by Maxon, Krieger and Sisko (J. Appl. Phys., 25, 971 (1954)) was constructed and improved so as to be used in oxygen-free atmosphere.The viscosities of non-Newtonian fluids were obtained from the ratio of shearing stress against rate of shear at any points on the flow curves.
The solvents, cupriethylenediamine and cuprammonium, are practically Newtonian.Whereas, the flow curves of cellulose solutions begin to deviate from linearity when the concentration exceeds a certain limit.The higher the degree of polymerization, the lower the limit concentration.The influence of rate of shear should be considered, when intrinsic viscosities are to be determined by the extrapolation of log (ηsp/c)-c plots.
One-point method
The one-point method as suggested by Wetzel, Elliot and Martin (Tappi, 36, 564 (1953)) and recently intended for practical use by Wilson (communication) gives intrinsic viscosities which are very conformable to those determined by the extrapolation method, so far as the degree of polymerization is not too high.The values were compared with those measured by the original Staudinger method.She differences are not too much.
The one-point method was tested also with cupramonium solutions.In various standard methods cuprammoniums varying markedly in composition are used. The constant k' of Martin's equation is sensitive to the copper content of the cuprammonium. If the proper value of k' is used, the one-point method affords very agreable values of intrinsic viscosities also for cuprammonium solutions of cellulose. The magnitudes of the constant to be used are : 0.30 for ACS, 0.31-0.32 for TAPPI and 0.35 for JIS cuprammonium.
