"Green" composites were successfully prepared from the thermoplastic cornstarch (TPCS) and activated-montmorillonite (MMT) by the method of blend extrusion. The thermoplastic cornstarch was plasticized with novel plasticizers urea and ethanolamine, and the activated-montmorillonites were obtained using ethanolamine as the activated solvent. The structure and morphology of "Green" composites were characterized by wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM), and transmission electron microscope (TEM). SEM and TEM images indicated that the composites presented reticulating fiber structure after being cooled by liquid nitrogen. The exfoliated MMT sheets in the composites acted as the inhomogeneous nucleation effect. The melting urea was crystaled over on the MMT sheets in the inducement of ethanolamine, and the column-shape crystal whisker overlapped together. Comparing with normal temperature, the mechanical properties of composites evidently improved after being cooled by liquid nitrogen, which was proved by the mechanical testing. The thermal stability and water-resistance of the composites also were studied in this paper. (c) 2005 Wiley Periodicals, Inc.