Starch–poly(ethylene‐co‐acrylic acid) composite films. Effect of processing conditions on morphology and properties

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Abstract
Formulations containing 4 parts cornstrach, 5 parts poly(ethylene‐co‐acrylic) (EAA), 1 part urea, and 1.6 parts of either water or aqueous ammonia were extruded at either 110–120°C or 150–160°C; and the resulting extrudates were then extrusion‐blown into films. Complex formation between EAA and starch was measured by either X‐ray diffraction or by solvent extraction of uncomplexed EAA. Although the processing temperature had only a minor effect on the amount of EAA complexed by starch, use of aqueous ammonia rather than water in these formulations increased the amount of complexed EAA by about a factor of 2. In films prepared with aqueous ammonia, the polysaccharide phase was present as submicron‐sized domains. When ammonia was omitted from these formulations, the polysaccharide phase was less uniform in size and contained particles that were over an order of magnitude larger than those observed with ammonia.