A STRAY FIELD MAGNETIC-RESONANCE-IMAGING STUDY OF THE DRYING OF SODIUM-SILICATE FILMS

Stray field magnetic resonance imaging (STRAFI) is shown to be highly suited to the study of drying processes in thin films. Sodium silicate films have been chosen as a model system exhibiting many of the prope rties of film drying in general. Films have been dried, as a function of temperature in the range 22 to 62 degrees C, down to water contents of order 28% by weight, at which stage the film is glassy. The experi mental results have been quantitatively analyzed by treating the dryin g film as a colloidal solution. The results suggest that the localized hydrogen spin-spin relaxation time, and hence the mobility of the wat er in the films is independent of the drying regime and depends primar ily on the local water concentration. (C) 1996 Academic Press, Inc.