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Development of photoinitiators
2021-06-02
1. Free radical-cation hybrid photoinitiator
The free radical research and development system cures fast, but shrinks greatly. While cationic light curing has small volume shrinkage, strong adhesion, the curing process is not blocked by oxygen, the reaction is not easy to terminate, and the "post-curing" ability is strong, suitable for light curing of thick films, but the curing speed is slow. Combining the advantages of the two, the free radical and cationic photoinitiator are formulated into a hybrid system, which can not only polymerize tourists with cationic polymerization, but also maximize the strengths and avoid weaknesses, and has a synergistic effect. Compatible use of two or more photoinitiators can achieve more satisfactory results.
2. Visible light initiator
Fluorinated diphenyl titanocene (Irgacure 784) and bis(pentafluorophenyl) titanocene have outstanding photoinitiation activity, storage stability and low toxicity, and their absorption wavelength has been extended to 500nm, which has a larger visible light region. Absorbing, it is particularly effective for visible light-initiated polymerization and curing of acrylic esters. In addition, due to the photobleaching effect of the titanocene light, the yellowing index of the film is small; and the deep curing is good, which is conducive to the thorough curing of the thick film. The activity of fluorinated diphenyl titanocene photoinitiator is 2~6 times higher than 2% Irgacure651 in the acrylate system.
3. Water-based photoinitiator (WSP)
The ammonium salt or sulfonate functional group is introduced into the common photoinitiator to make it compatible with water to make the water-based photoinitiator. The main types are aromatic ketones, including benzophenone derivatives, thioxanthone derivatives, alkyl aryl ketone derivatives, and benzyl derivatives.
4. Macromolecular photoinitiator
The common photoinitiator is introduced into the macromolecular chain to become the macromolecular photoinitiator, which has good compatibility with the resin, does not migrate after curing, is not easy to volatilize, and reduces the odor. Macromolecular photoinitiators can be divided into four types: side chain cleavage type, main chain cleavage type, side chain hydrogen abstraction type and main chain hydrogen abstraction type. Side chain cleavage type macromolecular photoinitiators are currently more successful.
5. Double curing
That is, the combination of light curing and other curing methods complements each other and highlights the advantages. It has fast curing at low temperature, excellent stability, can avoid separation and uncured, and obtain cured products with excellent mechanical properties and dimensional stability. The development of a dual curing system shared by light curing and other curing methods is effective in overcoming the weaknesses of light curing adhesives, expanding the scope of application and improving competitiveness. Other curing methods: thermal curing, moisture curing, oxidative curing, anaerobic curing, etc.
1. Free radical-cation hybrid photoinitiator
The free radical research and development system cures fast, but shrinks greatly. While cationic light curing has small volume shrinkage, strong adhesion, the curing process is not blocked by oxygen, the reaction is not easy to terminate, and the "post-curing" ability is strong, suitable for light curing of thick films, but the curing speed is slow. Combining the advantages of the two, the free radical and cationic photoinitiator are formulated into a hybrid system, which can not only polymerize tourists with cationic polymerization, but also maximize the strengths and avoid weaknesses, and has a synergistic effect. Compatible use of two or more photoinitiators can achieve more satisfactory results.
2. Visible light initiator
Fluorinated diphenyl titanocene (Irgacure 784) and bis(pentafluorophenyl) titanocene have outstanding photoinitiation activity, storage stability and low toxicity, and their absorption wavelength has been extended to 500nm, which has a larger visible light region. Absorbing, it is particularly effective for visible light-initiated polymerization and curing of acrylic esters. In addition, due to the photobleaching effect of the titanocene light, the yellowing index of the film is small; and the deep curing is good, which is conducive to the thorough curing of the thick film. The activity of fluorinated diphenyl titanocene photoinitiator is 2~6 times higher than 2% Irgacure651 in the acrylate system.
3. Water-based photoinitiator (WSP)
The ammonium salt or sulfonate functional group is introduced into the common photoinitiator to make it compatible with water to make the water-based photoinitiator. The main types are aromatic ketones, including benzophenone derivatives, thioxanthone derivatives, alkyl aryl ketone derivatives, and benzyl derivatives.
4. Macromolecular photoinitiator
The common photoinitiator is introduced into the macromolecular chain to become the macromolecular photoinitiator, which has good compatibility with the resin, does not migrate after curing, is not easy to volatilize, and reduces the odor. Macromolecular photoinitiators can be divided into four types: side chain cleavage type, main chain cleavage type, side chain hydrogen abstraction type and main chain hydrogen abstraction type. Side chain cleavage type macromolecular photoinitiators are currently more successful.
5. Double curing
That is, the combination of light curing and other curing methods complements each other and highlights the advantages. It has fast curing at low temperature, excellent stability, can avoid separation and uncured, and obtain cured products with excellent mechanical properties and dimensional stability. The development of a dual curing system shared by light curing and other curing methods is effective in overcoming the weaknesses of light curing adhesives, expanding the scope of application and improving competitiveness. Other curing methods: thermal curing, moisture curing, oxidative curing, anaerobic curing, etc.
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