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 aceton e were stronger but less flexible than those prepared in ethanol. Both types of films, however, were too brittle for most applications. Film s 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 resulte d in approximately a 2-3-fold increase in tensile strength values. Wat er vapor barrier properties were best for unplasticized zein films cro ss-linked with 20% polymeric dialdehyde starch. Incorporation of plast icizer into zein films resulted in an almost doubling in water vapor p ermeability values.