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 (CaCO 3 ) 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 105°C 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 (CaCO 3 ) 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 CaCO 3 level of 7.89%, respectively. Copyright © 2004 John Wiley & Sons, Ltd.