The ever-growing environmental pressure caused by the widespread consumption of petroleum based polymers and
plastics have spurred a thrust into the development of biodegradable or environmentally acceptable materials.
Biopolymers derived from various natural botanical resources such as protein and starch have been regarded
as alternative materials to petroleum plastic because they are abundant, renewable, inexpensive and biodegradable.
Domestic cultivation of soybeans has led a great deal of research into the development of biopolymers derived from
their byproducts, such as soy protein. Soy proteins are complex macromolecules containing 20 amino acids with many sites available for interaction with a plasticizer. Therefore, soy protein can be converted to soy protein plastic through extrusion with a plasticizer or cross-linking agent . Although the mechanical properties of soy protein plastic can be controlled and optimized by adjusting the molding temperature and pressure or processing
parameter and initial moisture content , the application of soy protein plastic is limited because of its low strength
and high moisture absorption. The most effective method is to blend soy protein plastic with biodegradable polymer to
form soy protein based biodegradable plastic. Currently, the biodegradable plastics being used to blend soy plastic
include polyester amide, polycaprolactone, Biomaxw, poly(tetramethylene adipate-co-terephthalate) [8–10],
whose processing window matches with that of soy protein plastic.