Abstract
The elongation or the creep of Du Pont's Maylar film (0.0065×25×100mm) in the aqueous solution of phenol was recorded automatically by means of a linear variable differential transformer (Fig. 1) at various concentrations and temperatures under a constant load (50g).
The elongation of the film (Δlt) increased exponentially with time at the initial stage and attained a limiting value (Δl∞) according to the concentration (c) of phenol at a constant temperature (Fig. 2). Δl∞ increased almost linearly with the increasing concentration, while it decreased with the increasing temperature (Fig. 3).
The logarithm of the time for half elongation (log t1/2) decreased linearly with increasing log c; the higher the temperature, the smaller the inclination was (Fig. 4).
After unloading, the film shrank instantly at first and then recovered slowly to a limiting length, Δl being about a half of Δl∞ (dotted lines in Fig. 2). This elongation of the unloaded film means swelling by phenol. The change in the weight of the film during the process of swelling increased with the increasing concentration (Fig. 7). The infrared absorption measurement suggested that the phenol molecules absorbed by the film combine with the polyester molecules by hydrogen bonding.
The creeping of Maylar film in the phenol solution was accelerated by neutral salts, i.e. sodium chloride, sodium acetate and sodium sulfate, but was retarded by potassium carbonate (Fig. 8). Surface active agents accelerated slightly the creep at low concentrations, but retarded considerably at high concentrations.
These results suggest that the swelling effect of phenol is closely related to its carrier effect in the dyeing process of polyesters.
