MORPHOLOGY AND MECHANICAL-BEHAVIOR OF ENGINEERING SOY PLASTICS

The morphology and mechanical behaviour of high protein content engine ering soy plastics are investigated. These engineering soy plastics ca n possess significantly higher Young's moduli (4.4 GPa) than those of petrochemical engineering plastics, if the moisture content in the soy plastics is kept low (<5% by weight). The low moisture soy plastic is found to be tougher than diglycidyl ether of bisphenol-A epoxy resins (0.96 MPa m(1/2) vs 0.8 MPa m(1/2)). The observed high fracture tough ness in the dry soy plastics is attributed to the formation of multipl e line arrays of cavitated voids (croids) in the damage zone. The form ation of croids may be associated with the presence of coagulated prot ein bodies (<0.05 mu m) in the soy plastics matrix. The ductility and dimensional stability of soy plastics is found to depend strongly on t he moisture content or the level of plasticizer utilized in the matrix . The biodegradable soy plastics show good potential as an alternative for replacing petrochemical, nonbiodegradable, plastics for engineeri ng applications. (C) 1997 Elsevier Science Ltd.