ON THE VISCOELASTIC PROPERTIES OF REGENERATE CELLULOSE FILAMENTS SPUN UNDER VARIOUS DEGREE OF STRETCHING

Abstract

The viscoelastic behavior of regenerate cellulose filaments spun under various degree of stretching were measured under normal air condition and swelling condition by water by using several longitudinal vibration methods over a range of frequency from subsonic to supersonic.
The results were represented in terms of relaxation spectrum over a range of relaxation time from 1 ×10^-6 to 1 sec.
Under normal air-condition, the relaxation spectrum is composed of wedge type portion in the range of relaxation time shorter than 1 × 10^-5 sec and of box type portion in the range longer than 1 × 10^-5 sec. In the range of wedge type the effect of stretching during spinning is hardly noticeable, while in the range of box type the higher the degree of stretching, the higher the intensity of spectrum is especially within the range of orientation factor of 20%.
Comparing the results under swelling condition with those under normal air, it is obvious that the real part of complex dynamic modulus is very much decreased in order with decreasing orientation factor of filaments while the imaginary part is not so much decreased as in the case of real part. The facts show that the relaxation spectrum in the time range longer than that covered here may be very much decreased with swelling in order with decreasing orientation factor, while the spectrum in the time range covered here is not so much affected. It may be considered that such a remarkable decrease of relaxation spectrum in the longer time range must be ascribed to destruction of hydrogen-bridge and to increase of chain mobility in the amorphous region due to swelling by water.