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The resiliency and modulus of viscose rayon as a function of swelling and temperature


  • Presented before the Fiber Society in Washington, D. C., October 28, 1960.


Resiliency and modulus measurements were made on viscose rayon yarn swollen to different extents in acetone–water mixtures. The resiliency was measured as a function of temperature and found to pass through a minimum at a temperature which is assumed to be the glass transition temperature (Tg) for the amorphous portion of the fibers. The effect of the degree of swelling on Tg was observed by changing the composition of the acetone–water mixture, and it was found that the Tg decreased with increased swelling. The plasticizing action of water apparently reduces the Tg from a value above the decomposition temperature (240°C.) for dry rayon to below 0°C. for water-wet rayon. At 21°C., the resiliency of rayon in acetone–water mixtures passed through a minimum as the water concentration changed. The concentration at the minimum corresponds to that which lowers the Tg to 21°C. Similar measurements were made on rayon immersed in polymer–water mixtures and in air at different relative humidities, and it was found that there were differences in the values of resiliency and modulus at equal water fugacities in the three media. Wet-state crosslinking lowered the Tg of rayon and increased the rubberlike elasticity above Tg. Dry-state crosslinking did not change Tg but greatly reduced the depth of the resiliency minimum. Both the modulus and the resiliency were increased over most of the range of water content by dry crosslinking.

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