Not that I am an ink chemist, but I believe your supplier was probably referring to free radical chemistry and cationic formulas. Free radical UV inks have acrylates and oligomers as their primary components, and are used in flexo, gravure, rotary letterpress and offset coatings. They also have a photoinitiator that will allow them to absorb UV light energy to be able to form free radicals, which in turn starts the polymerization process. They also have other additives such as silicones, waxes and other inhibitors.

     Cationic inks use very different epoxy resins and other monomers as the primary components as well as a photoinitiator. They do have similar additives as cationic inks. Cationic is the most common system used because it has more capabilities, and the raw materials are more readily available. They have better solvent, abrasion resistance and are more compatible with water-based inks. Cationic inks are claimed to have better adhesion and although longer to cure do give good barrier protection, and it is claimed the base materials are less toxic.