The influence of starch gelatinization on the rheological, thermal, and morphological properties of poly(ɛ-caprolactone) with corn starch blends

Blends of poly(ɛ-caprolactone) (PCL) with gelatinized and nongelatinized corn starch (PCL/starch ratios of 75/25, 50/50, and 25/75 wt.%) were prepared by mechanical processing and characterized by their melt flow index (MFI), water absorption (WA), differential scanning calorimetry (DSC), and light microscopy (LM). The MFI showed that the viscosity of the blends increased with increasing starch content and that gelatinized starch made the blends less viscous. Starch made the blends more susceptible to WA. The rupture of the starch granules caused by gelatinization increased the WA and the loss of soluble matter. DSC showed that starch reduced the crystallinity of PCL in the blends. LM showed good dispersion of the starch in the PCL matrix and also showed that the blends with nongelatinized starch had poor interfacial adhesion.