Spectroscopic methods for determination of latex content of coating layers

IR, Raman and UV methods were used to determine latex contents throughout different coating layers. The chosen methods have surface sensitivities from 1 to 8 micrometers, and the z-directional resolution of IR and Raman techniques is adjustable in the range of coating layer thickness. The ATR-IR, UV and confocal Raman microscope measurements gave, with certain limitations, latex contents of between 3 and 18 parts in clay and carbonate coatings. A study of calibration coatings showed hoe changes in coating pigments interfere with latex determination. Changes in pigment particle size and particle shape cause differences in signal intensity, especially in UV measurements. Clay in coatings gives rise to fluorescence, which interferes with Raman analyses. The results of these measurements will be used to give information on latex migration in coated papers.