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T HE MAIN objective of this research is to improve ink printability of papers via their modification with various types of water-based polymer latexes during paper manufacturing process. In order to achieve this target, various types of styrene-acrylate polymer latexes were used for modification of different types of papers. Styrene-acrylate latexes were prepared via emulsion polymerization of styrene with various acrylate monomers using emulsion polymerization technique. The effect of different emulsifying agents on the properties of the prepared emulsions was studied. The obtained results showed a significant improvement in degree of gloss and ink density on the polymer-coated papers which positively affect the ink ability, and ink holding properties of the modified paper. In addition, ink gloss and ink density of the coated papers improved with increasing the concentration of modifying latexes containing Texapon®P as emulsifier. These promising results open the way to use polymer latexes in treatment of documented value which can be used in stabilization of disappearing ink on paper leading to prevent forgery.

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The aim of this work is to compare between erasable and disappearing inks and study their role in the forgery of different documents. The obtained results showed differences between erasable and disappearing inks that help the documents examiner to deal with them when submitted in cases. The disappearing ink which contains phenolphthalein loses its color by time faster than that contains thymolphthalein. While the color of erasable ink did not generally change by time at room temperature but changed on exposure to UV light. On the other hand, the disappearing ink is absorbed by paper while erasable ink remains on paper surface. The two types of ink are more stable on polycarbonate polymer sheets. The polymer component of erasable ink is chemically bonded with polycarbonate polymer leading to ink stability. The presence of Ti in the pigment of disappearing ink acts as tag in forgery examination due to its diffusion inside polycarbonate sheet.