In the process of acid treatment, starch can undergo incomplete hydrolysis. The acid acts on the glycosidic bond to hydrolyze the starch molecules, the starch molecular chains are broken, and the starch molecules become smaller and become dextrin. Dextrin has fewer molecular chains, usually only a few dozen starch sugar molecular chains. The migration of dextrin in the gypsum board core is excellent, but it is easy to migrate to the outside of the tissue paper and affect the adhesion between the tissue paper and the gypsum board core, and the bonding of dextrin itself is not strong. Tests show that it is also not suitable as a gypsum board adhesive. Modified starch is also an incomplete hydrolysis product of starch. Its starch sugar molecular chain number is less than that of natural starch, and more than dextrin, usually between several hundred to several thousand. When the modified starch is heated, its viscosity gradually rises. When it is cooled, the viscosity of the modified starch increases slowly, the viscosity changes smoothly, and the final binding force is more remarkable.
The migration properties of modified starch can be well controlled. Most of the modified starch is migrated to the interface between the gypsum board core and paper. There is very little modified starch left in the gypsum board core. Similarly, it migrates into the paper. The amount of modified starch is also small. In the production process of gypsum board, adding less modified starch can firmly bond the gypsum board core and the surface paper together, which is an ideal gypsum board adhesive.