Quantifying Matting Agent Displacement in Package Printing Overprint Coatings
Quantifying matting agent displacement requires z-axis Raman depth profiling and strict viscosity recovery control to stop gloss drift and scuff failure.
Confocal Raman Microscopy
Analytical Technique
Spectroscopic imaging techniques provide non-destructive, high-resolution chemical mapping of multi-layer materials with sub-micron spatial resolution. Utilizing confocal raman microscopy allows researchers to identify the distribution of polymers, pigments, fillers and binders within a coated paper or board sample. This analysis is conducted by combining laser excitation with a confocal pinhole that blocks out-of-focus light from other depths.
Layer Analysis
Depth profiling of complex laminated structures is achieved by shifting the focal plane of the laser through the sample thickness. As the laser penetrates different depths, the scattered light provides a distinct vibrational spectrum for each material layer, such as polyethylene barriers, ethylene vinyl alcohol barriers, clay coatings and starch-based adhesives. This non-invasive cross-sectioning replaces traditional physical slicing, which often deforms the delicate interfaces of thin multi-layer films.
Processing the resulting spectral data generates clear cross-sectional images that show the thickness and uniformity of each barrier layer.
Surface Assessment
Surface chemical analysis helps identify the root causes of printing and adhesion failures on paperboard substrates. Localized accumulation of wax, silicone, plasticizers and unbound ink binders on the surface of the sheet can be mapped to explain poor ink transfer or dry rub resistance. Identifying these compounds through confocal raman microscopy ensures that mills can adjust their coating formulations or drying profiles to maintain consistent surface chemistry across production runs.