Meaning
Photoactive compound used to initiate polymerisation in ultraviolet curing systems. 2-isopropylthioxanthone initiates the crosslinking of resins by absorbing light and generating free radicals. The chemical stops being active once the light source is removed or the initiator is consumed.
Migration Probability
Transfer of the substance occurs when the ultraviolet dose is insufficient to anchor the molecules within the polymer network. Because 2-isopropylthioxanthone is a small molecule, it can move through the plastic matrix and reach the surface of food packaging. This transfer often results from the set-off effect where the printed outer side of one sheet touches the food-contact side of another in a stack.
Curing Performance
Efficiency in high-speed printing depends on the rate at which the initiator reacts to the specific wavelengths of the lamp. 2-isopropylthioxanthone works well with pigmented inks that would otherwise block the light because it absorbs in the longer ultraviolet spectrum. If the concentration is too low, the surface remains tacky and the part may fail adhesion tests.
Formulation Impact
Cost considerations often dictate the ratio of this initiator relative to cheaper alternatives in the resin blend. While 2-isopropylthioxanthone is effective, its presence can impart a slight yellow tint to clear coatings. This aesthetic change is acceptable in industrial components but might be rejected in high-clarity cosmetic packaging.
Proper levels ensure that the resin reaches its full tensile strength and chemical resistance within milliseconds. The chemical remains a standard choice for inks used on non-porous plastic substrates.
