STUDIES ON LOWERING OF THE SWELLING DEGREE OF RAYON

Abstract

As a preliminary test for a continuous heat-treatment, four tire-cord rayons and a textile rayon were treated in batch system at 130_??_200°C for 2.5 min. as follows: Samples of 800mg each were put into a small stainless steel autoclave containing water, which was closed tightly. Quick heating and cooling of the content were carried out by pouring the autoclave in an oil bath maintained at the desired temperature and taking it out of the bath followed by showering with cold water. The following results were obtained:(1) The degree of swelling, Q, of tire-cord rayon dropped to 1.6_??_1.7 from the original value of 1.7_??_1.8, while that of the textile rayon to 2.0 from 2.45.(2) The greater part of the lowering of the degree of swelling occurred within 2.5 min. of heating and elongation of the heating time was not so effective.(3) The decrease of DP was negligible at the temperature lower than 170°C, but it became obvious when the temperature was raised to over 170°C.(4) The depolymerization proceeded according to the Sharples' theory: 1/DPt-1/DPo=Kαt, where α is accessibility of the rayon, t the time of heating, K the velocity constant. The activation energy of the depolymerization reaction was 32.5 kcal/mole, which coincides nearly with the value of hydrolysis of cellulose in homogeneous acid solution.(5) The moisture regain of the rayon decreased very slightly by the treatment.(6) Iodine sorption J decreased as did the degree of swelling whereJ and Q were in linear proportion.