What are the factors that affect the effect of light curing?
The factors affecting the photopolymerization rate mainly include the activity and concentration of the photoinitiator, monomer reactivity (reactive group structure, functionality, monomer structure), reactivity of the photocurable resin, and radiation curing conditions (including light intensity, light source) Distribution intensity of each main output wavelength, anti-oxidation and anti-polymerization measures, etc.). Some of the above factors also have an impact on the final polymerization conversion rate. Prolonging the irradiation time appropriately can increase the conversion rate. Under normal circumstances, the effective radiation time is only a few seconds to tens of seconds. Excessively increasing the radiation time has little effect on improving the conversion rate. Various factors of impression curing may restrict each other and affect the curing effect together. There are many factors that affect the photocuring process, and the more common ones are mainly as follows:
What are the factors that affect the effect of light curing?
1. Sample thickness
The thickness of the film has a significant influence on the light curing, and the thickness of the light curing layer is limited by the viscosity of the coating and the coating process conditions. When the layer is thick, due to the light absorption and shielding effect of the photoinitiator itself, its fragments, resin, etc., it may cause incomplete curing of the bottom layer and affect the overall performance of adhesion.
2. Temperature effect
Properly increasing the temperature of the irradiated place is often conducive to the photocuring of the layer to a higher conversion rate.
3. The influence of photoinitiator concentration and type
Photoinitiator is a key part of the light-curing coating formula. Too low concentration is not enough to produce a higher curing rate, and it is not conducive to anti-oxygen inhibition; if the initiator concentration is too high, the residual amount after light curing is too large. The anti-yellowing and anti-aging properties of the layer are unfavorable, and the residual initiator is more likely to separate out of the cured film, which affects the appearance.
4. The effect of thinner is
The reactive diluent is used to reduce the viscosity of the coating and can improve the performance of the cured layer. At the same time, the reactive diluent also has a significant effect on the light curing process.
5. Dark response characteristics after irradiation
The post-irradiation dark reaction characteristics of cationic light-curing are well-known, but the dark aggregation and behavior of free-radical light-curing systems after irradiation are often overlooked.
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