Photoinitiator classification, 4-Benzoylphenyl Methacrylate is a photoinitiator

Photoinitiator, also known as photosensitizer or photocuring agent, is a kind of compound that can absorb energy of a certain wavelength in the ultraviolet region (250-420nm) or visible region (400-800nm), produce free radicals, cations, etc., thus triggering the polymerization and crosslinking of monomer curing. Photoinitiator products are mainly used in radiation curing technology. Light curing technology is a new green technology in the 1960s. Photoinitiator is the key material in light curing system. It forms formula products with active diluents, oligomers, auxiliaries and other raw materials, and then applies to end users. Although the amount of photoinitiator is not large, it plays an important role in the photocuring system.

The key development direction of photoinitiator is ybrid photoinitiator, visible light initiatore, water based type, macromolecular type and so on.

1、Free radical - cationic hybrid photoinitiator

The free radical system has a fast curing speed but a large shrinkage. And cationic light curing volume shrinkage, strong adhesion, curing process is not hindered by oxygen polymerization, the reaction is not easy to stop, "after curing" ability is strong, suitable for thick film light curing, but the curing speed is slow. Combining the advantages of the two, the hybrid system of free radical and cationic photoinitiator can not only induce cationic polymerization of free radical polymerization, but also make full use of advantages and avoid disadvantages, which has a synergistic effect. More satisfactory results can be obtained when two or more photoinitiators are used together.

2、Visible light initiator

Fluorinated diphenyltitanyl (Irgacure 784) and bis (pentafluorophenyl) titanyl (Irgacure 784) have outstanding photoinitiation activity, storage stability and low toxicity, their absorption wavelength has extended to 500nm, there is a large absorption in visible light region, especially effective for visible light induced polymerization and curing of acrylate. The yellow index of the film is small because of the photobleaching effect under the light. And the deep curing is good, which is conducive to the thorough curing of thick film. In the acrylate system, the photoinitiation efficiency of 0.2% was 2~6 times higher than that of 2%Irgacure651.

3、Water based photoinitiator (WSP)

Aryl ketones, including diphenyl ketone derivatives, thioxanone derivatives, alkyl arone derivatives, benzoyl derivatives, etc.

4、Macromolecular photoinitiator

The introduction of ordinary photoinitiator into the macromolecular chain, it becomes a macromolecular photoinitiator, its good compatibility with resin, curing after no migration, not volatile, reduce the smell. Macromolecular photoinitiators can be divided into four types: side chain cracking type, main chain cracking type, side chain hydrogen grabbing type and main chain hydrogen grabbing type. Side chain cracking type macromolecular photoinitiators are more successful among the existing categories.