What are the six additives commonly used in UV coatings?

January 7, 2023 Longchang Chemical

What are the six additives commonly used in UV coatings?

UV cationic and UV free base materials are very different, but the overall composition is similar. The cationic system is mainly epoxy materials, but the ordinary bisphenol A epoxy reaction speed is slow, with more applications of alicyclic epoxy / oxetane materials; free radical system commercialization is now very mature, with epoxy / polyester / polyurethane modified acrylate materials can provide more choice of solutions.

UV cationic systems have fewer raw material options than free radical systems, and low viscosity alicyclic epoxy resins are the main polymers. Take alicyclic epoxy resins as an example.

TTA21 of various purity specifications is the most dominant product in the UV coating industry. As the application of cationic UV coatings/applications continues to grow significantly, it is foreseen that the amount of alicyclic epoxy resins represented by TTA21 will increase.


In the specific product applications of inks/coatings, in addition to both needing UV light to provide curing energy, the two systems reflect major differences in performance performance and reaction characteristics.


1. Oxygen-blocking effect

UV cationic system does not have the effect of oxygen-blocking, but more afraid of water, moisture will affect the curing efficiency of cationic system; UV free radicals on the contrary, by the oxygen-blocking influence.


2. Substrate adhesion

Usually in the more difficult to adhere to the surface of the substrate, such as glass / metal / high-density plastic, UV cation than UV free base has better adhesion performance.


3. Volume shrinkage rate

UV free radical system formulation curing shrinkage rate is generally above 10%, while UV cation system can control the shrinkage rate of 1-3%, is a good solution to solve the volume shrinkage.


4. Dark curing characteristics

UV cation system can continue to react to the inner layer after stopping the light source irradiation, to complete the material after curing, this is the dark curing characteristics, very suitable for thick coating applications, heating the cation after curing speed is significantly helpful; UV free radical is a stop-and-go reaction system.


5. Contact safety

UV cation system reaction degree is close to 100%, safety can be REACH / FDA testing certification, can be used in food packaging and other related fields.


6. Light curing speed

In general the UV free radical system curing speed than the cationic system, affected by oxygen-blocking products cationic surface drying will be faster, but the actual drying speed is not as fast as the free radical, you can promote the reaction by heating, and eventually can reach a very good degree of completion.


Formulation notes


UV cation system can be mixed with UV free radical system in any proportion, called UV hybrid system, can improve the relative curing speed of UV cation and UV free radical shrinkage, affected by oxygen barrier and other shortcomings, the same film thickness of the system curing energy difference is not large.


UV cation system is to rely on the initiator generated by Lewis strong acid to do the active point of the ring-opening reaction, the formula will commonly affect the initiator activity of the material is mainly azo organic pigments (can be modified to do protection), and free radicals mixed with TPO/819/907 and other structures containing P, S and other elements of the initiator, and similar to 115 multi-level amine.


Humidity on the UV cationic system curing influence, control the ambient humidity within 50% is appropriate; while heating will speed up the reaction speed.



UV Photoinitiator Same series products

Product name CAS NO. Chemical name
Sinocure® TPO 75980-60-8 Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide
Sinocure® TPO-L 84434-11-7 Ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate
Sinocure® 819/920 162881-26-7 Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide
Sinocure® 819 DW 162881-26-7 Irgacure 819 DW
Sinocure® ITX 5495-84-1 2-Isopropylthioxanthone
Sinocure® DETX 82799-44-8 2,4-Diethyl-9H-thioxanthen-9-one
Sinocure® BDK/651 24650-42-8 2,2-Dimethoxy-2-phenylacetophenone
Sinocure® 907 71868-10-5 2-Methyl-4′-(methylthio)-2-morpholinopropiophenone
Sinocure® 184 947-19-3 1-Hydroxycyclohexyl phenyl ketone
Sinocure® MBF 15206-55-0 Methyl benzoylformate
Sinocure® 150 163702-01-0 Benzene, (1-methylethenyl)-, homopolymer,ar-(2-hydroxy-2-methyl-1-oxopropyl) derivs
Sinocure® 160 71868-15-0 Difunctional alpha hydroxy ketone
Sinocure® 1173 7473-98-5 2-Hydroxy-2-methylpropiophenone
Sinocure® EMK 90-93-7 4,4′-Bis(diethylamino) benzophenone
Sinocure® PBZ 2128-93-0 4-Benzoylbiphenyl
Sinocure® OMBB/MBB 606-28-0 Methyl 2-benzoylbenzoate
Sinocure® BP 119-61-9 Benzophenone
Sinocure® 754 211510-16-6 Benzeneacetic acid, alpha-oxo-, Oxydi-2,1-ethanediyl ester
Sinocure® CBP 134-85-0 4-Chlorobenzophenone
Sinocure® MBP 134-84-9 4-Methylbenzophenone
Sinocure® EHA 21245-02-3 2-Ethylhexyl 4-dimethylaminobenzoate
Sinocure® DMB 2208-05-1 2-(Dimethylamino)ethyl benzoate
Sinocure® EDB 10287-53-3 Ethyl 4-dimethylaminobenzoate
Sinocure® 250 344562-80-7 (4-Methylphenyl) [4-(2-methylpropyl)phenyl] iodoniumhexafluorophosphate
Sinocure® 369 119313-12-1 2-Benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone
Sinocure® 379 119344-86-4 1-Butanone, 2-(dimethylamino)-2-(4-methylphenyl)methyl-1-4-(4-morpholinyl)phenyl-
Sinocure® 938 61358-25-6 Bis(4-tert-butylphenyl)iodonium hexafluorophosphate
Sinocure® 6992 MX 75482-18-7 & 74227-35-3 Cationic Photoinitiator UVI-6992
Sinocure® 6992 68156-13-8 Diphenyl(4-phenylthio)phenylsufonium hexafluorophosphate
Sinocure® 6993-S 71449-78-0 & 89452-37-9 Mixed type triarylsulfonium hexafluoroantimonate salts
Sinocure® 6993-P 71449-78-0 4-Thiophenyl phenyl diphenyl sulfonium hexafluoroantimonate
Sinocure® 1206 Photoinitiator APi-1206

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