How to solve the problem of incomplete curing of UV coating?

January 5, 2023 Longchang Chemical

How to solve the problem of incomplete curing of UV coating?

UV coating technology has become the mainstay of green coatings because of its environmental friendliness, high efficiency and high hardness, and is inevitably and increasingly accepted in a wide range of applications. The range of substrates it can be applied to has evolved from wood and paper to plastics, metals, ceramics, glass and other fields.


UV curing principle and characteristics

UV curing (UV curing), refers to the strong ultraviolet light irradiation, the system of photosensitive substances in the chemical reaction to produce active fragments, triggering the system of active monomer or zwitterionic polymerization, cross-linking, so that the system from the liquid coating instantly into a solid coating. curing process is a photochemical reaction process, that is, under the action of ultraviolet light energy, prepolymer In a very short period of time cured into a film, UV light in addition to causing the surface curing of the material, more penetration into the liquid UV-curable ink, and stimulate the further curing of deep ink; compared with traditional ink, UV-curable ink polymerization and drying more thoroughly, without any evaporation or solvent-based contaminants, 100% curing. UV curing technology has been developed rapidly in the world, and rapidly in Electronics, printing, construction, decoration, medicine, machinery, chemical and automotive industries to promote the application.


UV curing technology is widely used mainly because of its unique advantages: it cures quickly, catering to the needs of modern automated production; pollution-free, in line with the direction of development of modern coatings and inks; high quality coating film, high hardness, scratch resistance, corrosion resistance and other advantages and has attracted much attention.


Here we discuss the six factors that affect the incomplete UV light curing


1, the energy of ultraviolet light.

(1). UV light energy is insufficient, generally because the uv lamp production power density is too small, or with the transformer parameters do not match, thus causing incomplete curing.

(2). UV coatings in the photoinitiator is not enough to absorb reasonable UV energy, resulting in incomplete curing.


2. The temperature inside the UV furnace is too low.

UV furnace due to excessive air volume of the centrifugal fan, or the role of excessive water cooling, the oxygen blocking situation is too strong, resulting in the UV lamp surface temperature is too low to work properly, resulting in incomplete curing of UV coatings.


3, the distance of the light curing lamp.

UV lamp and reflector and the distance between the surface of the illuminated object in 7 ~ 8cm when the strongest UV energy, but according to the different curing substrates, the general curing distance is selected at about 10 ~ 15cm.

(1). Distance is too low, because the UV lamp surface temperature is very high, the substrate is deformed by heat.

(2). Distance is too high, UV energy is small, the surface of the substrate is not dry and sticky.


4, the thickness of the UV coating.

UV coating thickness plays a key role in the effect of UV curing, according to the paint hue, temperature, curing speed, substrate surface and other different conditions for appropriate deployment.

(1). The coating is too thick, the drying time is relatively long under the irradiation of the same power light source, on the one hand, it affects the deep drying of UV coating, on the other hand, it will make the surface temperature of the substrate too high, leading to the deformation of the substrate.

(2). The coating layer is too thin, which will lead to poor surface gloss of the product and fail to achieve the required surface effect.


5. Speed of conveyor belt of coating line.

According to the different substrates, coatings and curing distance, the speed of the equipment conveyor belt, i.e. the speed of light curing, should be adjusted appropriately.

(1). Curing speed is too fast, the substrate surface UV coating sticky or surface dry but not dry inside.

(2). Slow running speed, the surface of the substrate will age.


6, the environment of light curing process.

UV coating viscosity changes greatly due to temperature, so the room temperature should be adjusted, generally controlled at 15-25 ℃ is more appropriate, the temperature is too low will produce orange peel phenomenon, and pay attention to the printing can not be exposed to direct sunlight.


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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