Starch application as dry strength additives in papermaking

Starch is a complex combination of carbohydrates that is insoluble in water and composed from Amylose and Amylopectin. The paper strength increases by refining, wet pressing and additives. Refining increases the paper strength about 98-99 percent but decreases the tear strength. Also more energy is consumed as a result of refining operations. Starch derivatives are considered as a common paper dry strength additives that are used in today's paper manufacturing industry. Using starch as dry strength additives increases the paper hydrogen bonds between the fibers and thus improves the strength and quality of the resulting paper. Constituent fibers of the paper are mostly anionic to increase the durability of the starch on paper’s fiber, starch molecules must bind to cationic groups. Results have shown that cationic starch in paper increases the resistance to rupture, bursting, and tensile strength. Cationic starches have some advantages such as good capability of diffusion, high penetration and high adsorption on the fibers.