Liquid penetration as a simple detection method for structural differences in particulate films prepared from slurries

We have investigated the use of liquid penetration to evaluate and detect structural differences in dried thin films. Two different films were fabricated from slurries that consisted of solid particles and a polymer. Both slurries had the same composition, but were prepared using different mixing processes. Clear differences in the void distributions of the as-prepared films were observed using mercury porosimetry. No significant differences were observed after the films were compressed. However, cross-sectional scanning electron microscopy images showed clear structural differences, including segregated particles after compression. Liquid penetration times into the films were measured and explained using a modified kinetic model. The wettability of the films using solvents of low polarity was also evaluated and was found to be dependent upon the extent of segregation within the films. This result suggested that liquid penetration measurements could be used as a simple method to evaluate the structure of particulate films. [Display omitted] •Mixing condition of slurry strongly affects internal structures of dried film.•Liquid penetration time depends on the extent of segregation of particles in films.•Kinetic model for our experimental system was derived from the Washburn equation.•Good agreement between our kinetic model and measured data for liquid penetration.•Liquid penetration as a simple method to evaluate internal structures of films.