Preparation and properties of halloysite nanotubes/plasticized Dioscorea opposita Thunb. starch composites

A traditional Chinese medicine, Dioscorea opposita Thunb. is rich in starch, which was isolated and used to prepare the plasticized starch (PS). And PS was composited with halloysite nanotube (HNT) by the casting process. Amylose content of native starch was about 24.5%, and the granules were in the size of about 20 μm. The starch showed the typical B-type with relative crystallinity of 26.9%. According to the characterization of the composites with scanning electron microscope, mechanical tensile testing, rapid visco-analyser, thermogravimetric analysis and water vapor permeability, HNT could obviously improve the pasting viscosity, mechanical properties, thermal stability and water vapor barrier of the composites. When HNT contents varied from 0 to 9 wt%, the tensile strength increased from 3.9 to 9.7 MPa, and the water vapor permeability decreased from 8.48 × 10−10 to 6.61 × 10−10 g m−1 s−1 Pa−1 at RH 75% and from 14.54 × 10−10 to 11.7 × 10−10 g m−1 s−1 Pa−1 at RH 100%.