Influence of surfactants in aqueous-based polymeric dispersions on the thermomechanical and adhesive properties of acrylic films.

Good adhesion between a polymeric film and the surface of a solid substrate is critical to the performance of coated pharmaceutical products. Previous research has shown that tablet wettability by an organic-based cellulosic solution could predict the extent of film-tablet adhesion. Using an aqueous-based acrylic polymeric dispersion, the current study investigated the relationship between film adhesion and tablet wettability. Up to 10% (w/w based on dry polymer weight) polysorbate 80 or sorbitan monooleate was incorporated into the film-coating formulations. While the contact angle between the polymeric dispersion and the tablet surface was dependent on the type and concentration of surfactants added to the coating formulation, no correlation between tablet wettability and polymer adhesion could be established. The addition of surfactants to formulations containing the hydrophobic plasticizer tributyl citrate (TBC) caused lowering of the glass transition temperature of the polymer. Increased force of adhesion, elongation at adhesive failure, and adhesive toughness, however, were noted only in the TBC-plasticized films containing polysorbate 80. These findings demonstrate that our understanding of the mechanisms involved in film-tablet adhesion is still quite limited.