Response surface optimization of the feed compositions of biodegradable packaging foams

Response surface methodology (RSM) was used to analyse the effects of polyvinyl alcohol (PVOH) and calcium carbonate (CaCO3) on the physical and mechanical properties (radial expansion ratio, bulk density, 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 125°C with a feed rate of 27.8 l/h, screw speed of 215 r.p.m. and die diameter of 3.92 mm. Responses were most affected by changes in PVOH levels and to a lesser extent by CaCO3 levels. Individual contour plots of the different responses were overlaid. An optimum radial expansion ratio of 3.39, bulk density of 0.065 (g/cm3), compressibility of 32.27(N), and spring index of 0.906 were identified at 36% PVOH and 5% CaCO3.