Effects of processing conditions on nanoclay dispersion in starch-clay nanocomposites

Wheat starch samples containing Cloisite Na+ and 30B nanoclays were extruded from a twin-screw extruder. Moisture content, temperature, and screw speed were varied to determine their effect on nanoclay dispersion. X-ray diffraction and transmission electron microscopy (TEM) were used to examine nanoclay intercalation and exfoliation. Moisture content had the largest effect on Cloisite Na+ dispersion, with the highest moisture sample containing exfoliated nanoclays. Meanwhile, temperature and screw speed had little effect on Cloisite Na+ dispersion. For Cloisite 30B samples, only an increase in temperature produced slight intercalation of nanoclays. This was due to the incompatibility of starch with the more hydrophobic Cloisite 30B. Also, Cloisite Na+ and 30B intercalation did not depend on specific mechanical energy. In addition, water absorbance tests indicated the Cloisite Na+ sample containing the most welldispersed nanoclays had the lowest water uptake.