ARS researchers have developed a way to prepare shrink films made from renewable and biodegradable resources. Modified starches, such as waxy corn starch, are completely dissolved or dispersed in water. Next, vinyl or acrylic compounds, are mixed with the starch under specific conditions to achieve graft polymerization. The starch-poly(methyl acrylate) graft copolymers can then be extrusion blown into thin films using conventional methods. When the film is wrapped around an object and exposed to high humidity, it uniformly shrinks around the contours of the object without forming breaks, tears, holes, bubbles, or striations. The shrink film is very stable at room temperature and humidity, and yet can also be removed easily by soaking for a few minutes in warm water. The advantage of using this technology verus plastic shrink films is that it doesn’t require the use of heat.

Shrink films can be made to fit the contours of irregularly shaped articles, and are widely used in the packaging industry. Most shrink films are made from petrochemicals. The long-term uncertainty of prices and supplies of petroleum and environmental concerns have increased interest in alternative sources of raw materials for making plastics.

The technology is applicable to the packaging industry. Particularly, the technology is useful in the packaging of irregularly shaped, highly polished, abrasion-sensitive, or heat-sensitive objects, including glassware, porcelain, tools, scientific instruments, fruit, and other food products. This technology contains a synthetic plastic.

Please refer to USPN 4,839,450 (Docket #0959.87), "Moisture-Shrinkable Films from Starch Graft Copolymers," which issued June 13, 1989.

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