Characterization of Penetration of Solvents into Press Blankets by Confocal Laser Scanning Microscope

The interaction of printing press blankets with ink oils and solvents can influence the printing results and the integrity of the blanket. Little has been reported on the penetration rate of various solvents into commercial blankets. A new method to characterize penetration rate is proposed here. Three different blankets are contacted with three solvents. A technique is developed where a fluorescent dye is added to the solvents to allow the position of the solvent to be detected with a confocal scanning laser microscope (CLSM). Top views of the samples reveal the distribution of the solvent within the surface structure of the blanket. The distribution does correlate with the blanket textures. Images of physical cross sections show that different solvents interact and penetrate into the blankets at different rates. These rates did not correlate to the contact angle of the solvent and the blanket but does relate to the relative densities of the samples as determined with back scatter electron images. The aliphatic solvent did not penetrate into one blanket type at all. Toluene penetrated to the rubber-fabric interface in 72 hours. The penetration rate seems to fit a diffusion mechanism.