AKD stands for Alkyl Ketene Dimer, which is a sizing agent used in the paper industry. Sizing agents are chemicals that are applied to paper or paperboard to improve their resistance to water penetration. AKD is one of the commonly used sizing agents.

AKD is a cationic (positively charged) chemical compound that is derived from fatty acids. It is usually synthesized by reacting fatty acids with ketene gas, resulting in the formation of AKD. The AKD is then used as a sizing agent by adding it to the papermaking process.

When AKD is added to the paper pulp, it reacts with the cellulose fibers present in the pulp to form a thin hydrophobic (water-repellent) film on the surface of the fibers. This film reduces the absorbency of the paper and prevents water from penetrating into the paper, making it more resistant to liquid penetration and improving its strength and durability.

The use of AKD as a sizing agent offers several advantages. It provides excellent water repellency, enhances the printability of paper, improves ink holdout, reduces paper dusting, and enhances the dimensional stability of the paper. AKD is also relatively easy to handle and has low toxicity, making it a preferred choice in the paper industry.

Overall, AKD is an important sizing agent used in the papermaking process to improve the water resistance and performance of paper products.