Laser-induced Plasma Emission Spectroscopy (lips): a Useful Analaytical Tool for the Surface Chemical Characterization of Coated Paper Materials

A nontraditional method for chemical analysis of light weight coated (LWC) grade paper is described. Laser-induced plasma emission spectrometry (LIPS) produces three-dimensional profiles of coatings and fillers. The technique ablates the coating from the top to the paper base with a laser beam. LIPS provides spatial resolution and characterization of the chemical homogeneity of the paper coating and relates that information to the efficiency of the coating method. It provides information on binder migration which is a hindrance for improved stable coatings. Herein, several commercial LWC paper grades and their base papers were analyzed. Pigment identification of light weight paper coatings, coat weight distribution maps, and profiles were obtained. Blade and film coating generate different coating distribution profiles that are detected by LIPS. The phenomenon of binder migration was demonstrated by observing its masking effects on Si spectra. An investigation of filler content in base papers involved analysis of base paper used in LWC grades. The papers represented two different types of formers, but because of confidentiality issues, little else was revealed. A significantly higher amount of filler was observed at the surface of the base stock in Former A than in Former B, as indicated from Mg spectra of the filler.