Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2006
Publication Date: 5/12/2006
Citation: Chiou, B., Yee, E., Wood, D.F., Shey, J., Glenn, G.M., Orts, W.J. 2006. Effects of processing variables on nanoclay dispersion in starch-clay nanocomposites. Cereal Chemistry. 83(3):300-305. Interpretive Summary: The addition of nanoclays into various synthetic and natural polymers had resulted in improved moisture resistance properties. The best results were obtained for samples containing well-dispersed nanoclays. The nanoclays acted as a barrier to water molecules and inhibited their diffusion through the material. In this study, we wanted to improve moisture resistance of starch-based materials for use as disposable containers by incorporating nanoclays into them. We produced wheat starch-nanoclay composites using a twin-screw extruder and determined the main factors affecting nanoclay dispersion during extrusion. We varied moisture content, temperature, and screw speed and characterized nanoclay dispersion by using X-ray diffraction and transmission electron microscopy. Moisture content had the largest effect on nanoclay dispersion with the highest moisture content sample containing the most well-dispersed nanoclay. In contrast, temperature and screw speed had little effect on nanoclay dispersion. In addition, the sample with the best dispersed nanoclay had the lowest water uptake.
Technical Abstract: 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 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 well dispersed nanoclays had the lowest water uptake.