Chemical Stability
Unreacted chemical components remaining in a coating after exposure to ultraviolet light can migrate through the board or affect the recyclability of the material. Uv cured lacquer residues are the monomers or photoinitiators that did not form into a solid polymer chain during the drying process. These traces can cause odors or pose a safety risk if the packaging is used for food products.
They are often detected using solvent extraction and gas chromatography.
Migration Risk
Chemical compounds that remain liquid within the solid coating layer are free to move through the porous structure of the paperboard. When uv cured lacquer residues are present in high concentrations, they can contaminate the contents of the package or cause the ink to remain tacky. This problem is often caused by old lamps or a conveyor speed that is too fast for the light intensity.
Testing for these residues is a standard requirement for pharmaceutical and food grade packaging. Producers must ensure a high degree of polymerization to avoid these issues.
Curing Efficiency
Modern curing lamps reduce the presence of these residues in finished coatings. Consistent monitoring of the lamp output prevents the shipment of under-cured material. This verification is essential for maintaining the safety and quality of the packaging.
