How to Make a Biodegradable Styrofoam From Cassava Starch

Biodegradable foams from plants such as cassava might replace traditional Styrofoam products.

Styrofoam has proved to be an extremely useful material since its commercial production began in the 1940s. Its cheap manufacturing cost, light-weight water-resistant surface and ability to absorb vibrations have made it an abundant material. Its resistance to natural degradation, high recycling cost and environmentally harmful manufacturing process motivated scientists and businesses to find affordable, biodegradable alternatives. Cassava is an inexpensive South American plant that is rich in starch and can be a viable source ingredient for biodegradable composite materials.

Things You'll Need

• Thermo-pressing system
• Teflon mold
• Cassava starch
• Dolomite lime
• Fine sawdust
• Guar gum
• Magnesium stearate
• Saline solution

Instructions

1. Mix equal amounts of the cassava starch and dolomite lime.

2. Add, in a separate container, about 100 ml of water for each gram of the powder created in Step 1.

3. Mix sawdust into the water, and let it soak for five minutes. Use about 1 gram of sawdust for every 20 grams of the mixed starch/lime powder. This measurement might require experimentation, because the source plant effects the ideal percentage. Pine, aspen and eucalyptus fibers have been used successfully but with varying ideal measurements.

4. Add the starch/lime powder to the water.

5. Add a small amount of guar gum and magnesium stearate, and stir the mix thoroughly. Use between one to two parts per 100 grams for each. The guar gum will prevent the solids from separating, and the magnesium stearate will facilitate separating the foam from the mold.

6. Pour the mixture into the Teflon mold and insert it into the thermo-pressing system.

7. Heat the mold at about 400 degrees F under 0.36 MPa of pressure for about three minutes. These figures might require some experimentation depending on the shape of your mold and desired thickness of the foam. While under pressure, the steam created from the heat will cause the material to develop a porous structure.

8. Remove the foam from the mold once it has cooled.

9. Soak the foam in saline solution for several days in a stable, room-temperature environment to condition the surface and prevent the release of chemicals from the foam.

References

• "Characterization of Foams Obtained from Cassava Starch, Cellulose Fibres and Dolomitic Limestone by a Thermopressing Process"; Vivian Consuelo Reolon Schmidt, João Borges Laurindo; 2010
• "Biodegradable foams made of cassava starch and fibers : Influence in the mechanical properties"; Dulcerc F. Parra, Laura G. Carr, Patricia Ponce, Carmen C. Tadini, Ademar B. Lugao; 2006
• Purdue.edu: Cassava