Effects of propionyl content on the morphology, mechanical properties, and biodegradability of esterified cassava starch/polycaprolactone blends

The chemical structure of cassava starch was modified via an acylation with two different reaction systems: propionic anhydride in an aqueous sodium hydroxide solution and propionic anhydride in dimethyl sulfoxide/triethylamine mixtures. The acylation was carried out by the variation of reaction parameters to generate modified starches with a variety of propionyl contents. After that, the modified starch was blended with polycaprolactone (PCL) at a 30/70 weight composition in a twin‐screw extruder. The results from the tensile testing of the various modified starch/PCL blends show that the moduli and tensile stresses of the materials were higher than those of the unmodified starch/PCL blend. The elongation values of the modified starch/PCL blends, however, decreased with the propionyl content. Scanning electron micrographs of the blends containing modified starch with 62 and 80% propionyl were also different from those of blends containing modified starch with 16 and 28% propionyl in term of phase contrast. Finally, the rate of biodegradation of the blends decreased with increasing propionyl content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2154–2162, 2005