moisture - shrinkable films can be extrusion blown from flour - poly graft copolymers . the films shrink when exposed at room temperature to relative humidities approaching 100 %. the films have potential application in shrink - wrapping irregularly shaped articles without application of heat . easy removal of the films by water washing is another feature suitable for this use . this invention allows the use of unmodified cereal flour in lieu of gelatinized starch as the substrate for graft polymerization . this substitution greatly simplifies the preparation and isolation of the graft copolymers and reduces the expense of the process by lowering raw material costs .