UV curing technology has revolutionized the printing industry, offering faster curing times, increased productivity and reduced energy consumption. However, the presence of oxygen during the curing process can have a significant impact on the performance of UV curing of inks.
Oxygen inhibition occurs when oxygen molecules interfere with free radical polymerization, resulting in incomplete curing and compromised ink performance. This phenomenon is particularly pronounced in inks that are thin and have a high surface area to volume ratio.
When UV curable inks is exposed to ambient air, oxygen molecules dissolved in the ink formulation and oxygen diffused from the air can interfere with the polymerization process. The low concentration of dissolved oxygen is easily consumed by primary reactive free radicals, resulting in a polymerization induction period. On the other hand, oxygen constantly diffusing into the ink from the external environment becomes the main cause of inhibition.
The consequences of oxygen inhibition can include longer curing times, surface adhesion and the formation of oxidized structures on the ink surface. These effects can reduce the hardness, gloss and scratch resistance of the cured ink and affect its long-term stability.
To overcome these challenges, researchers and UV LED manufacturers have explored various strategies.
The first is to change the reaction mechanism. By improving the photoinitiator system, surface oxygen inhibition of the cured ink can be effectively suppressed.
Increasing the concentration of photoinitiators is another way to mitigate the effects of oxygen inhibition. By adding more photoinitiators, the ink formulation becomes more resistant to oxygen inhibition. This results in higher ink hardness, better adhesion and higher gloss after curing.
In addition, increasing the intensity of the UV curing equipment in the curing equipment helps mitigate the negative effects of oxygen inhibition. By increasing the power of the UV light source, the curing process becomes more efficient and compensates for the reduced reactivity caused by oxygen interference. This step must be carefully calibrated to ensure optimal curing without damaging the substrate or causing other adverse effects.
Finally, oxygen inhibition can be mitigated by adding one or more oxygen scavengers to the printing equipment. These scavengers react with oxygen to reduce its concentration, and the combination of a high intensity LED UV curing system and the oxygen scavenger can minimize the impact of oxygen on the curing process.With these improvements, manufacturers can achieve better curing performance and overcome the challenges of oxygen inhibition.
Post time: Jan-19-2024