(730a) Investigate Soy Protein As Plastic Component in Polymer Blends

Feng Chen, Jinwen Zhang

School of Mechanical and Materials Engineering & Composite Materials and Engineering Center

Washington State University, Pullman, WA 99164

Abstract

Soy protein (SP) has been recognized as a promising alternative to petroleum-based plastic materials. However, owing to some obstacles such as water/moisture sensitivity, high melt viscosity, narrow process window and/or brittleness, SP plastics based-on neat SP have little practical values. To overcome these disadvantages, blending SP with other biodegradable polymers has received increasing attention. However, SP has only been investigated as organic filler in these blends. Although these blends display higher water resistance, processibility and/or toughness than neat SP plastics, the stiffness of the resulting blends are not satisfactory and the strength is often lower than that of both the neat SP plastics and the neat polymer.

In this work, soy protein concentrate (SPC) was blended with poly(butylene adipate-co-terephthalate) (PBAT) in a single-step compounding process. The mixing of the blends was carried out by extrusion compounding and test specimens were prepared by injection molding. Different influence of SPC as a plastic component and filler on phase structure and mechanical properties of the resulting blends were investigated. The intrinsic cause-deformability of soy protein and extrinsic cause-melt shear stress and interfacial tension in phase morphology development of PBAT/SPC blends were discussed. SP percolation network structure was noted in the blends with SP processed as plastic component. Owing to the extensive crosslinking of the SP molecules, the resulting blends actually became in situ formed polymer/SP composites. The composition-processing-structure-property relationship in soy protein blends were studied in detail.  Resulting blends demonstrate an overall superior performance when SPC is used as plastic.