Chemical Degradation
Process where light sensitive molecules in ultraviolet inks decompose into smaller fragments or byproducts after exposure to a curing lamp. This photoinitiator breakdown is the necessary first step in the polymerization reaction that hardens the coating on the paper surface. However, the resulting chemical fragments can sometimes lead to unwanted odours or potential migration issues if the reaction is not managed.
Curing Efficiency
Intensity of the ultraviolet light and the concentration of the initiator determine the speed and completeness of the chemical change. When photoinitiator breakdown is insufficient, the ink remains tacky and can smear or set off onto the back of the next sheet in the stack. Over exposure can also lead to problems, as the board may become brittle or the coating may discolour due to excessive degradation of the organic components.
Proper lamp maintenance prevents these defects.
Migration Analysis
Identification of the specific byproducts formed during the curing process is necessary for ensuring the safety of food packaging. Laboratories use chromatography to detect the residues of photoinitiator breakdown and verify that they do not exceed the migration limits. Some byproducts are more volatile than the original molecules, meaning they pose a higher risk of passing through the board to the product inside.
Residual fragments are quantified as part of the safety certification.
