Effects of plasticizers on the structure and properties of starch-clay nanocomposite films

Biodegradable nanocomposites were successfully fabricated from corn starch and montmorillonite (MMT) nanoclays by melt extrusion processing. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and film properties such as barrier, mechanical and thermal properties were also measured. As a conventional plasticizer, the influence of glycerol content was first investigated. As the glycerol content decreased from 20% to 5%, the degree of clay exfoliation increased. Films with 5% glycerol exhibited the lowest water vapor permeability (0.41 g mm/kPa h m(2)), highest glass transition temperature (53.78 degrees C), and highest tensile strength (35 MPa), but low elongation at break (2.15%). Urea and formamide were tested as alternative plasticizers for the starch-clay nanocomposites. The results indicated that the use of new plasticizers increased the degree of clay exfoliation. The formamide plasticized starch-clay nanocornposite films exhibited lower water vapor permeability (0.58 g mm/kPa h m(2)), higher glass transition temperature (54.74 degrees C), and higher tensile strength (26.64 MPa) than the other two plasticizers when used at the same level (15 wt%). (C) 2008 Elsevier Ltd. All rights reserved.