Effect of plasticizers on properties of pregelatinised starch acetate (Amprac 01) free films.

Film coating is a technique widely used in the pharmaceutical field to improve and modify technological and release characteristics of capsules, tablets and granules. In this paper physical and mechanical properties of free films of Amprac 01, obtained by the solvent cast method, were studied in order to investigate the film forming ability of this modified starch and the effects of the addition of different plasticizers. A morphological microscopical analysis (SEM) was performed to study surface properties of the films, while thermal analysis (DSC) was carried out to investigate the influence of different types of plasticizers on the glass transition temperature of the polymer. Then a mechanical characterization permitted to evaluate important parameters such as film crack resistance and deformation at break. Extensional creep/relaxation tests were also performed to investigate the viscoelastic characteristics. As clearly demonstrated by the T(g) values, the residual water present in the films acted as plasticizers, making possible the formation of free films characterised by good macroscopical and mechanical properties. Except glycerol, the kind and amount of the other tested plasticizers did not markedly improve the mechanical and crack resistance of the films.