Composition factors affecting the water vapor permeability and tensile properties of hydrophilic zein films

Transparent unplasticized zein films were prepared in aqueous ethanol or acetone. Tensile properties indicated that films prepared in acetone were stronger but less flexible than those prepared in ethanol. Both types of films, however, were too brittle for most applications. Films containing a glycerol:poly(propylene glycol) ratio of 1:3 exhibited elongation values almost fifty times greater than glycerol-plasticized films. Incorporation of cross-linking agents inter zein films resulted in approximately a 2-3-fold increase in tensile strength values. Water vapor barrier properties were best for unplasticized zein films cross-linked with 20% polymeric dialdehyde starch. Incorporation of plasticizer into zein films resulted in an almost doubling in water vapor permeability values.