Starch-based degradable plastic film

Starch from cereal grains such as corn and wheat shows promise as a component of plastics. especially where the introduction of a biodegradable component is important. For many years up to the early 70s, petroleum was readily available at $2 to $4 per barrel and starch sold for about 5 cents per pound. Since that time. petroleum has increased 5- to 10-fold while starch maintained a steady price or increased little more than 2-fold. These price changes and increased availability now make starch economically attractive as a substitute for petroleum.

Most common starches contain 17-27% amylose. a linear polysaccharide consisting of 400-1.000 1A-linked a-D-glucose units, and 73-82% amylopectin. a branched molecule consisting of D-glucose units linked a-D( 1-4) with branches at the C-6 position once every 26 or more D-glucose units. Starch readily gelatinizes (or disperses) in hot water to form a paste that can be cast into film. However, such films are sensitive to water and become quite brittle upon drying due to retrogradation of the starch. To alter these properties. starch has been blended with water-soluble plasticizers and synthetic polymers.

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10.05.2010. 23:50

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