SUPERCRITICAL-FLUID EXTRACTION OF POLYMERS - THEORETICAL EXPLANATION OF PRESSURE AND FLOW-RATE EFFECTS

A theoretical model is compared with experimental results for the supercritical fluid extraction (SFE) of additives and other small molecules from polymers. The model explains the transition between the two extreme situations in which either diffusion through the polymer or solvation in the supercritical fluid is the dominant rate determining process. From fitting the model to data obtained at varying pressure, information on diffusion coefficients and solubilities is obtained which shows the expected behaviour. Predictions by the model of the effect of flow rate are close to experimental observations. SFE from polymers can thus be understood successfully by use of the model.