Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2007
Publication Date: 5/1/2008
Citation: Tang, X., Alavi, S., Herald, T.J. 2008. Barrier and Mechanical Properties of Starch-Clay Nanocomposite Films. Cereal Chemistry. 85:433-439. Interpretive Summary: Citizens are requesting better use of our natural resources and to reduce landfill waste. One means to contribute to this effort is to offer a biodegradable packaging material as an alternative to petroleum based packaging material. To this end, starch (either corn, waxy corn, wheat or potato) and clay were blended and melted in mixer called an extruder. The extruder prepared the starch-clay blend or composite into very small particles called nanocomposites. The results indicated that corn-clay nanocomposites exhibited better mechanical properties (tensile strength, water vapor permeability) compared to nanocomposites prepared from other starch sources. Packaging materials is used in most consumer products. The impact of the research may limit our dependency on foreign petroleum used to produce these packaging materials. Additionally, the biodegradable nature of the starch-clay nanocomposite packaging material will place less stress on our environment.
Technical Abstract: The poor barrier and mechanical properties of biopolymer-based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch-clay nano-composites were synthesized by a melt extrusion method. Natural (MMT) and organically modified (I30E) montmorillonite clays were chosen for the nanocomposite preparation. The structures of the hybrids were char-acterized by X-ray diffraction (XRD) and transmission electron micros-copy (TEM). Films were made through casting using granulate produced by a twin-screw extruder. Starch/MMT composite films showed higher tensile strength and better water vapor barrier properties than films from starch/I30E composites, as well as pristine starch, due to formation of intercalated nanostructure. To find the best combinations of raw materials, the effects of clay content (0–21 wt% MMT), starch sources (corn, wheat, and potato), and amylose content (0, 28, 55, 70, 100%) on barrier and mechanical properties of the nanocomposite films were investigated. With increase in clay content, significantly higher (15–92%) tensile strength (TS), and lower (22–67%) water vapor permeability (WVP) were obtained. The barrier and mechanical properties of nanocomposite films did not vary significantly with different starch sources. Nanocomposite films from regular corn starch had better barrier and mechanical proper-ties than either high amylopectin or high-amylose-based nanocomposite films. WVP, TS, and elongation at break (%E) of the films did not change significantly as amylose content increased beyond 50%.