According to the composition of the UV-curable coating, during the photo-curing process, the phenomenon of incomplete curing is found in the coating layer. Why is this? From the analysis of the working principle of UV-curing, molecules must absorb light quantum with sufficient energy to become excited molecules. , Decomposes into free radicals or ions, and makes unsaturated organic compounds undergo polymerization, grafting, crosslinking and other chemical reactions to achieve the purpose of curing. What can affect the curing of the coating during this process?
The main factors that affect the curing degree of UV-curable coatings are the following:
1. The effect of UV light energy
During the curing process, if the UV energy of the photoinitiator in the supplied UV coating exceeds or is insufficient to affect the required energy, the supplied energy is scientifically greater than the required energy or it is blindly over-supplied, which will cause Negative effects of over-curing, such as explosion polymerization and anti-curing reactions. Therefore, the energy of the external light must be moderate, that is, neither excessive nor insufficient, which has caused the incomplete curing.
2, the effect of the distance of UV lamp curing
The distance between the UV lamp and the reflector and the surface of the illuminated object is 7-8㎝, which is the best curing distance (the strongest UV energy). However, depending on the curing substrate, the distance is generally about 10-15㎝. The distance is too low, because the surface temperature of the UV lamp is very high, the substrate is deformed by heat; the distance is too high, the UV energy is small, and the surface of the substrate is not dry and sticky. The curing distance must be appropriately adjusted with the substrate, coating, and lamp power. .
3.Effect of curing speed
Depending on the substrate, coating, curing distance, etc., the curing speed of the equipment is appropriately adjusted. The curing speed is too fast, the UV coating on the substrate surface is sticky or the surface is dry but not dry; the running speed is slow, and the surface of the substrate will age.
4, the impact of UV coating thickness
The thickness of the UV coating plays a key role in the effect of UV curing. The coating is too thick, and the drying time is relatively long under the same power light source. On the one hand, it affects the drying of the UV coating, on the other hand, it makes the surface of the substrate If the temperature is too high, the substrate will be deformed; if the coating is too thin, the surface gloss of the product will be poor. In addition, the hue, temperature, curing speed, substrate surface and other conditions of the thick coating of the UV coating need to be appropriately adjusted.
5. Impact of working environment
UV coatings have large changes in viscosity due to temperature, so room temperature should be adjusted. Generally, 15-25 ° C is more suitable, and it should not be exposed to direct sunlight during printing.
