Effect of citric acid and processing on the performance of thermoplastic starch/montmorillonite nanocomposites

A facile two steps extrusion processing conditions are used to prepare thermoplastic starch (TPS)/glycerol modified-montmorillonite (GMMT) nanocomposites. X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrate glycerol can enlarge the d-spacing and destruct the multilayer structure of montmorillonite (MMT) effectively using high speed emulsifying machine (HSEM) in the first modification step. So the enlarged d-spacing and destructed platelets of MMT are favorable to form intercalated or exfoliated TPS/GMMT nanocomposites in the second melt extrusion processing. However, scanning electron microscopy (SEM) and XRD show the possible competition between TPS matrix and plasticizer for the intercalation between MMT layers can deteriorate the plasticization of TPS. In addition, citric acid (CA) can increase the plasticization of TPS and dispersion of MMT in nanocomposites effectively detected by fourier transform infrared (FT-IR) spectroscopy and SEM. At the same time, this facile processing conditions and CA can improve the mechanical properties and water vapor permeability (WVP) of TPS/GMMT nanocomposites obviously.