EFFECT OF EXTRUSION PROCESSING ON PROPERTIES OF ZEIN–FATTY ACIDS SHEETS
The feasibility of applying extrusion technology to the processing of zein–fatty acids resins was investigated. Zein 
resins were prepared in the laboratory by mixing zein and fatty acids (1:0.75 w/w) in an aqueous ethanol solution followed 
by the recovering and drying of plasticized zein into a granular solid. Granular resins were melted in a twin–screw extruder 
and collected as large pellets, which were immediately rolled into sheets. A response surface experimental design was 
followed to investigate the effect of three extrusion parameters (barrel temperature, screw speed, and amount of solvent added 
during extrusion) on mechanical properties of the resulting sheets. Zein resins were uniformly melted and flowed smoothly 
through the extruder barrel. Mechanical properties of sheets prepared by extrusion were comparable to those of samples 
prepared by a previously described bench–top 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. High 
temperatures increased tensile strength but decreased elongation at break of resulting sheets. The storage stability of zein 
sheets was also investigated. Zein sheets maintained their mechanical properties after three months of storage at room 
temperature, indicating their stability in storage. SEM images of sheet external and cross–section surfaces seemed to show 
an entanglement of fiber–like structures. Further research is needed to determine sheet morphology.