Effect of Extrusion Processing on Properties of Zein?fatty Acids Sheets

The feasibility of applying extrusion technology to the processing of zeinfatty acids resins was investigated. Zeinresins were prepared in the laboratory by mixing zein and fatty acids (1:0.75 w/w) in an aqueous ethanol solution followedby the recovering and drying of plasticized zein into a granular solid. Granular resins were melted in a twinscrew extruderand collected as large pellets, which were immediately rolled into sheets. A response surface experimental design wasfollowed to investigate the effect of three extrusion parameters (barrel temperature, screw speed, and amount of solvent addedduring extrusion) on mechanical properties of the resulting sheets. Zein resins were uniformly melted and flowed smoothlythrough the extruder barrel. Mechanical properties of sheets prepared by extrusion were comparable to those of samplesprepared by a previously described benchtop method, indicating the feasibility of extrusion for processing of zein resins.Extrusion temperatures included in the experiment affected mechanical properties and water resistance of zein sheets. Hightemperatures increased tensile strength but decreased elongation at break of resulting sheets. The storage stability of zeinsheets was also investigated. Zein sheets maintained their mechanical properties after three months of storage at roomtemperature, indicating their stability in storage. SEM images of sheet external and crosssection surfaces seemed to showan entanglement of fiberlike structures. Further research is needed to determine sheet morphology.