Starch is a kind of completely biodegradable polysaccharide natural polymer that is widely used at present. It has the advantages of wide material sources, low price and easy biodegradability. It occupies an important position in the field of biodegradable materials. But the disadvantage is that the water resistance of starch-containing degradable plastics is not good, the wet strength is poor, and its performance will be reduced when exposed to water.
       What is the effect of different moisture content on the crystallinity of corn starch granules?
       X-ray diffraction method was used to study the crystallinity of corn starch granules with different moisture content. Only in the glassy state, the amorphous region of starch produces X-ray diffraction patterns. The intensity and area of ??the diffraction peaks depend on the water content of the starch to some extent.
       The X-ray diffraction pattern of corn starch granules is composed of two parts: microcrystalline area and amorphous area. As the moisture content increases, the crystallinity of the sample increases from small to large, and reaches an equilibrium value (about 45%).
       At room temperature, when the moisture content is at a low level (less than 11.25%), the amorphous region in the corn starch granules is in a glassy state, and the diffraction pattern shows a combination of the two parts of the microcrystalline region and the amorphous region.
       When the moisture content is at a high level (greater than 18.55%), the amorphous region in the starch granules is in a rubbery state, and the X-ray diffraction pattern is only formed by the microcrystalline region. At lower moisture content, the increased moisture content due to plasticization will result in the formation of more crystallites.