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Ecofriendly substitutes for polystyrene

Rigid, custom-fit foam pieces like those that keep computer monitors firmly in place inside cardboard boxes during shipping could be made with eco-friendly starch from potatoes, wheat or corn, instead of from petroleum, according to Agricultural Research Service (ARS) research plant physiologist Gregory M. Glenn. Opting for starch in place of petroleum-derived polystyrene would lessen America's dependence on petroleum.

Glenn works at the ARS Western Regional Research Center in Albany, Calif. For nearly two decades, he has been developing and patenting innovative, "green" techniques for transforming commonplace plant starches—like the silky white cornstarch kept in kitchen cupboards everywhere—into convenient, biodegradable foamed goods like shipping liners, dinnerware and more.

Co-inventor Simon K. Hodson collaborated with Glenn in developing two recent technologies. Both approaches yield strong, durable, and versatile biofoams that look like familiar polystyrene foam goods. Like those conventional foams, the biofoams can be manufactured to a range of densities and can be die-cut or molded into a seemingly limitless array of shapes, sizes and thicknesses.

Both patent-applied-for technologies for making biofoams rely on an extruder—a standard piece of equipment—to heat and mix starch and other all-natural compounds. With one option, the extruder squeezes out long strings, called "thermoplastic melt," that are later cut into small beads about half the size of a marble.

At various points in the process, the beads puff and expand, such as when they are put into the cavity of a heated mold to press them into the desired shape. Expanded beads eventually touch one another, creating a strong matrix that's much like the bead matrix of polystyrene foams.

The biofoams aren't waterproof, but a moisture barrier, made from plant sources such as corn, can be added, ensuring that the finished foam is still derived exclusively from renewable,

by S. C.
18 september 2009, Food & Fun > Nature