Cellulose acetate solubility plot

I he simplest is the partition of a solute between two immiscible solvents. In this case [0] /[Z)], = K, where K is the partition coefficient. This equilibrium is often referred to as the Nernst distribution. When [Z)], is plotted against [Z)], at constant temperature the curve is a straight line which terminates at the point when both the fibre and the dyebath are saturated. There are slight deviations from the linearity of the curve, particularly as the solutions become more concentrated. This system is probably exhibited in its ideal form when dyeing cellulose acetate rayon from an alcoholic dye solution, but it is also essentially true in the case of the application of disperse dyes in aqueous suspension to cellulose acetate, because the dyes are all soluble in water to a very limited extent and the undissolved particles act as a reservoir to maintain the concentration of the solution. The curve for this isotherm is shown in Fig. 12.14. 

If this assumption is seriously in error, the actual mixed gas mobility selectivity of cellulose acetate may be even lower than indicated by the diffiisivity ratios in Table 20.3-1. Polymers such as cellulose acetate which are solubility selectors may tend to display plasticization-type responses in the permeability versus pressure plots such as that shown in Fig. 20.3-2h. More detailed sorption and diffiision data on a single, well-characterized film sample for this interesting system are needed badly to investigate these effects further. Understanding the principles at play in the case of cellulose acetate may permit expansion of the ranks of such solubility selecting materials for possible use as thin-film composite membranes or in blending with other, more plasticization-resistant membrane materials. 

FIGURE 3.3 Hansen solubility plot (three-dimensional) for cellulose acetate (Hansen, 2007), with Hansen partial solubility parameters, 8, 8p and 8h, in MPa. See Figure A3.28 for the same data plotted in a ternary Teas chart. 

---