Effects of α‐amylase and glycerol levels on the composition optimization of poly(β‐hydroxybutyrate‐ co ‐valerate)/starch blended biodegradable resin analyzed with response surface methodology

Response surface methodology was used to analyze the effects of the enzyme level ( X 2 ) and glycerol level ( X 1 ) on objective attributes [water solubility index (WSI), water absorption index (WAI), and maximum loading ( Y 3 )] of a cornstarch/poly(β‐hydroxybutyrate‐ co ‐valerate) blended composite. A rotatable central composite design was used to develop models for the objective responses. The experiments were run at barrel temperatures of 160, 160, 165, and 165°C, with a screw speed of 40 rpm and complete feeding (filling ratio = 1). Responses were most affected by changes in X 2 and to a lesser extent by X 1 . Individual contour plots of the different responses were overlaid, and regions meeting the optimal WSI of 8.73%, WAI of 3.94 g of gel/g of dry weight, and Y 3 of 304.17 N were established at an X 2 of 5.43 g and an X 1 of 120.79 mL. These predicted values for the optimal process conditions were in good agreement with the experimental data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011