Characteristics of photoinitiators
UV-curing technology is characterized by less environmental pollution, fast curing speed, low energy consumption. It is the fastest growing market segment in the ink, coating, printing and packaging fields. UV-curing resin system is mainly composed of photoinitiator, reactive oligomer, active diluent and other additives. Photoinitiator is the key component of uv-curing resin system, which plays a decisive role in curing rate. According to different reaction mechanism, photoinitiators can be divided into free radical type and cationic type.
The free radical – initiated system has the fast curing speed, but its volume shrank greatly. The cationic – initiated system has small volume shrank, strong adhesion. Curing process is not blocked by oxygen, the reaction is not easy to terminate, “after curing” ability is strong, suitable for thick film curing, but curing speed is slow.
Combining the advantages of the two system, a hybrid system of free radical and cationic photoinitiator can produce both free radical polymerization and cationic polymerization.Two or more photoinitiators can be used together, the effect will be better.