Starch acetate: A novel film-forming polymer for pharmaceutical coatings

Starch acetates (SA) have been investigated as novel, multifunctional excipients for the direct compression tableting process. In this study, the film‐forming ability of SA (DS 2.8) and the effect of commonly used plasticizers on the physical properties of SA films were evaluated. The results were compared with the properties of ethylcellulose (EC). Free films were prepared by a solvent‐cast method. Mechanical studies, water vapor and drug permeability tests, and thermal analysis (DSC) were used to characterize the film‐forming ability of SA and efficiency of tested plasticizers. SA films were tougher and stronger than EC films at the same plasticizer concentration. Also, in most cases, the water vapor permeability of SA films was lower than that of EC films. DSC thermograms supported the findings of the tensile test: plasticizers with several small ester groups (e.g., triacetin and triethyl citrate) were the most compatible with SA. Due to the good mechanical properties, low water vapor, and drug permeabilities of the films, SA seems to be a promising film‐former for pharmaceutical coatings. The toughness of SA films may result from their dense film structure, which is due to strong interaction forces between adjacent SA molecular chains.