Vol. 2 7, No. 2 /January 14, 1998 ISSN 0300-757X

BIODEGRADABLE COMPOSITE PLASTICS BASED ON SOY

Melt-away waste is a consumer society's collective dream. Researchers at Iowa State University are closer to making that dream come true with the advent of moisture-resistant soy protein plastic composites that could be used in food packaging, medical implants and sporting goods. The biggest barrier to viable soy protein plastics has been the material's natural tendency to absorb water and dissolve in moist environments. The Iowa State group led by Joshua Otaigbe blended soy protein plastic with a nontoxic polyphosphate filler supplied by Coming, tailoring the formula to last in water for a year. The success of the project hinged on joining the plastic and the filler. Otaigbe accomplished this by employing a coupling agent (g-aminopropyltriethoxy silane (A 1100)), which reacts spontaneously with water or -OH groups of glycerol to form silanols (I). Through a number of subsequent reactions, these silanols eventually facilitate polysiloxane and polymer-matrix bond formation. The bonded structure interface between the polymer and the fillers is resistant to water. After soaking the sample for 12 months in water under ambient conditions, the team observed a dramatic reduction in the intrinsic water absorption tendency of the composite. Because the composite constituents are biodegradable and nontoxic, the composite can be composted and returned to the soil as nutrients after its service life has expired. In medical applications, it may be possible to use these composites to make surgical implants. Blending the composite constituents with synthetic bioabsorbable polymers such as lactic acid, glycolic acid and polycaprolactone will also provide polymer alloys and composites with enhanced properties. Otaigbe's team has filed an invention disclosure and is looking for funding and development partners.

Details: Joshua Otaigbe, Assistant Professor, Materials Science and Engineering Dept., Iowa State University, 3053 Gilman Hall, Ames, 1A 50014. Phone: 515-294-9678. Fax: 515-294-5444. Internet: otaigbe@ iastate.edu.