Effects of extrusion temperature and moisture content on mechanical properties of starch-based foams
1999
Cha, J.Y. | Chung, D.S. | Seib, P.A.
Blends composed of wheat and corn starch, poly(ethylene-co-vinyl alcohol), polystyrene, plasticizers, and nucleating and blowing agents were equilibrated at several relative humidities and extruded at several temperatures and 100 rpm screw speed using a single screw, C. W. Brabender laboratory-scale extruder. Bulk compressibility, bulk resiliency, and relaxation time of the starch-based foams were studied. A mathematical model was developed to predict bulk compressibility of the starch-based foams using a dimensional analysis method. Bulk compressibility decreased as extrusion temperature and moisture content increased; whereas, the rate of relaxation in stress relaxation test increased. Bulk resiliency increased as extrusion temperature increased and moisture content decreased. The mechanical properties of starch-based foams compared to those of commercial polystyrene foams. The results indicated the optimum extrusion temperatures of the blends for making foamed cushioning materials (bulk compressibility: 120 to 300 N, bulk resiliency: 65 to 100%): 150 degrees C for a blend using normal wheat starch, and 160 degrees C for a blend using hydroxypropylated wheat starch.
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