The preparation and properties of dialdehyde starch and thermoplastic dialdehyde starch

Dialdehyde starch (DAS) is prepared by periodate oxidation of starch, and DAS with different aldehyde contents is plasticized by glycerol to obtain thermoplastic DAS (TPDAS). DAS is characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystalline starch is destroyed and oxidized to form amorphous DAS, while amorphous starch inside of starch granules is degraded. As a result, DAS containing 93.05% aldehyde content formes a ring shape. Compared to thermoplastic native starch, the re-crystallization of DAS can not take place in TPDAS during the storage period, because periodate oxidation has destroyed the crystallization of starch. With the increasing of aldehyde contents of DAS, the tensile strength and the resistance of both moisture absorption and water vapor permeability of TPDAS are improved. It is ascribed to the cross-linking of aldehyde groups in TPDAS.