DRY AND WET STRENGTHS OF POLYMERIC FILMS PREPARED FROM AN AQUEOUS COLLOIDAL POLYMER DISPERSION, EUDRAGIT RS30D

The mechanical properties of polymeric films are traditionally evaluat ed on dry cast or sprayed films. In this study, films were cast from a n aqueous colloidal polymer dispersion [poly(ethylacrylate thylmethacr ylate-trimethylammonioethylmethacrylate chloride) copolymer, Eudragit RS30D]. The mechanical properties were measured not only in the dry bu t also in the wet state by a puncture test, wherein a puncturing probe was driven through the dry or wet film. The puncture strength and elo ngation at puncture were measured as a function of crosshead speed, fi lm thickness, type and concentration of the plasticizer (triethyl citr ate or acetyl tributyl citrate), and storage humidity. The puncture st rength decreased and the elongation increased with increasing plastici zer concentration with dry films. An HPLC assay was used to determine the amount of plasticizer in the polymer -films before and after expos ure to an aqueous medium in order to correlate the plasticizer content in the films with the resultant mechanical properties. Triethyl citra te, a water-soluble plasticizer, leached from the polymeric films resu lting in significant changes in the mechanical properties when compare d to dry or wet films prepared with the non-leaching, water-insoluble acetyl tributyl citrate. The mechanical properties of the films were a ffected by the storage humidity.