39—sorption of Water by Viscose Rayon at Low Humidities

Sorption data are presented for moisture regains below ½ per cent at 25–65° C for a commercial viscose rayon. The adsorption isotherm is reproducible provided that whenever the rayon is dried most of the water is removed at not too high a temperature. Hysteresis effects are reported in cycles of adsorption-desorption of up to only 1–2 per cent regain. This is of interest in that capillary mechanisms are inadmissible in this region and swelling effects are likely to be very small or negligible. The low humidity adsorption isotherms may be approximately described by means of the Freundlich equation. The isosteric heat of adsorption is calculated from the data.