Spectroscopic methods for determination of latex content of coating layers

IR, Raman and UV methods were used to determine latex contents throughout d ifferent coating layers. The chosen methods have surface sensitivities from 1 to 8 micrometers, and the z-directional resolution of IR and Raman techn iques 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 is parts in clay and carbonate coatings. A study of calibration coatings showed how changes in coating pigments inter fere with latex determination. Changes in pigment particle size and particl e shape cause differences in signal intensity, especially in UV measurement s. Clay in coatings gives rise to fluorescence, which interferes with Raman analyses. The results of these measurements will be used to give informati on on latex migration in coated papers.