Phase inversion in plane membranes. II. A direct comparison between experiments and evaporation model predictions
✍ Scribed by Carlo Castellari
- Book ID
- 103057926
- Publisher
- Elsevier Science
- Year
- 1988
- Tongue
- English
- Weight
- 748 KB
- Volume
- 69
- Category
- Article
- ISSN
- 0011-9164
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✦ Synopsis
The drying of acetone-cellulose acetate solutions is analyzed using a computer simulation model. The evaporation model takes into account both a timevarying surface concentration and a concentration dependence of the diffusion coefficient. The flux of solvent at the polymer-air interface is calculated by means of the experimental weight-loss curves presented in Part I of the work. The model predicts four basic system variables that include the dependence of both diffusivity and activity of the solvent on the concentration. A comparison between theory and experiments indicates that the predicted dependence of the self-diffusion coefficient agrees, in general, with the one obtained by tracer measurements. However, as long as the thickness of the cast film increases, a growing discrepancy between the observed and predicted values of the parameter D* (0) is found. The reason for the discrepancy is probably the uniform film-thinning limiting assumption. The polymer-solvent interaction parameter found by means of the numerical procedure seems to be underestimated. This inadequacy could be considered a consequence of the assumptions introduced in determining the solvent activity.