China's National Development and Reform Commission encourages the development of products with low VOCs content, and eliminates and restricts the use of solvent-based adhesives, coatings and other products with high VOCs content. Among them, radiation curing and water-based are the two mainstream trends in the development of low VOCs materials.
Radiation curing has the advantages of fast curing speed, simple process, green and environmental protection, etc., and is widely used in coatings, adhesives, 3D printing and other fields. Radiation curing technology is generally divided into UV free radicals, UV cations, and free radical/cation mixed curing systems, providing more solutions with different performance for downstream applications.
1)
UV cations vs UV radicals
Curing performance comparison UV cationic.
Most radiation curing systems are still acrylic systems. Not only the curing shrinkage is large, but it can also cause internal stress in the coating or adhesive components during the curing process, reduce the bonding strength, and even cause local cracking and warping. Therefore, reducing or even eliminating the volume shrinkage during the curing process is of great significance for improving the bonding strength of coatings or adhesives.
The UV cationic system has the advantages of low shrinkage and no oxygen inhibition, which can perfectly improve the problem of UV free radicals. The following is a detailed comparison of the differences in performance and reaction characteristics between the two systems:
2)
Cationic curing resin
The UV cationic system is mainly based on alicyclic epoxy resin and oxetane. Alicyclic epoxy resin refers to a resin in which the epoxy group is directly connected to the alicyclic structure. It has low viscosity, good thermal stability, low halogen content, excellent electrical properties, UV resistance and yellowing resistance, and UV curing is oxygen-free. Advantages such as polymerization inhibition and low migration.
3)
UV cationic curing application fields
UV cationic curing has many advantages such as oxygen-free polymerization inhibition, low viscosity, and excellent bonding. It is widely used in coatings, inks, adhesives, 3D printing and other fields.