Composition optimization of extruded starch foams using response surface methodology

Response surface methodology (RSM) was used to analyse the effect of polyvinyl alcohol (PVA) and calcium carbonate (CaCO3) on the objective attributes (shipping bulk density, radial expansion ratio, compressibility and spring index) of a biodegradable cushioning extrudate. A rotatable central composite design (CCD) was used to develop models for the objective responses. The experiments were run at 105degreesC with a feed rate of 27.8 l/h, screw speed 500 r.p.m. and die diameter 3.92 mm. Responses were most affected by changes in polyvinyl alcohol (PVA) levels and to a lesser extent by calcium carbonate (CaCO3) levels. Individual contour plots of the different responses were overlaid, and regions meeting the optimum shipping bulk density of 6.00 kg/m(3). radial expansion ratio of 3.30, compressibility of 43.71 N, and spring index of 0.91 were identified at the PVA level of 20.23% and the CaCO3 level of 7.89%, respectively. Copyright (C) 2004 John Wiley Sons, Ltd.