The co-plasticization effects of glycerol and small molecular sugars on starch-based nanocomposite films prepared by...

In this study, starch-based nanocomposite films (SNF) made with small molecular sugars (sucrose, fructose and glucose) and glycerol as co-plasticizers were prepared by extrusion blowing. The incorporation of sugars into SNF inhibited the formation of intercalated structures, as shown by X-ray diffraction (XRD) data. XRD analysis also showed that the relative crystallinity of the films decreased after the addition of sugars. Compared to control films, SNF made with sugars showed higher water vapor permeability (WVP, 4.78 × 10^-10 g.m/m².s.Pa), as well as a lower tensile strength and glass transition temperature (T_g, -14.2 °C). Fourier transform infrared (FTIR) analysis revealed that there were high levels of hydroxyl groups and water molecules aggregated around the starch polymer chains. Sugars played an important role in the melting and fracturing of starch granules, as confirmed by scanning electronic microscopy (SEM) data. For the films with sugars especially for glucose, the vertical elongation at break achieved 142%, representing approximately 76% enhancement in elongation at break value compared to the control film, which has almost reached basic standard of traditional plastics (V/H-E ≥ 150%). Thermoplastic starch films co-plasticized with sucrose (TPS-suc) presented better performance than those co-plasticized with fructose (TPS-fru) or glucose (TPS-glu).