An Automatic Tester for Determining Degree of Ripeness of Viscose

The conventional Hottenroth index (H.I.) method for determining the degree of ripeness of viscose is very useful for viscose industries, but has a few inevitable shortcomings. In order to avoid these shortcomings and to control the ripening process more easily, an automatic tester was developed by one of us (S.O.). The principle of the tester is to record automatically the change in consistency of viscose sample during titration with salt solution; the change in torque required for stirring the sample viscose at constant velocity is converted to the change in electrical potential by means of a differential transformer device. Employing this tester, some rheological properties of viscose with added various salt solutions, especially ammonium chloride solution, were studied, and it was concluded that the conventional H.I. method did not always determine a volume of 10% NH4Cl solution by which coagulation of sample viscose just set in. On the oher hand, it was found that viscose with added ammonium chloride solution manifested thixotropic nature, and that the H.I. by the usual method represented a volum of 10% NH4Cl solution by which a viscose sample became notably thixotropic. Further studies were carried out for the practical application of this tester to the viscose industry, because it was desirable to correlate the H.I. with the characteristic point in coagulating curve obtained by this tester. It was found that when higher concentrations of viscose (viscose 30g: water 20ml) and ammonium chloride solution (13.5%) were chosen the plot of the logarithm of torque against the volume of NH4Cl solution added gave a broken straight line and the break point coincided very well with the H.I. given by the conventional method.