PROPERTIES AND MICROSTRUCTURE OF PLASTICIZED ZEIN FILMS

A new method for preparation of zein films involving plasticization of zein with oleic acid to form an intermediate moldable resin was prese nted. The resin was stretched over rigid frames to form thin membranes that were set in flexible films. The objective of the study was to in vestigate the effect of film preparation method on film properties. Te nsile properties, microstructure, and thermal behavior of zein films p lasticized with oleic acid were investigated for films prepared by con ventional casting from ethanol solutions and by stretching of plastici zed resins. Cast films were stiff and brittle, whereas resin films sho wed more flexibility and toughness. Differential scanning calorimetry thermograms of cast films indicated phase separations were generated w hen heated that were not observed for resin films. Microstructure imag es showed a higher degree of structure development and orientation in resin than in cast films. Glass-transition temperatures of resin films were measured at -94 and 104.4 degrees C, indicating the film remaine d flexible through a wide temperature range. Resin film flexibility an d toughness were attributed to effective plasticization that led to fi ber formation and orientation.