Guide to UV Measurement
Cure
Cure is one of the most used and least understood terms in our lexicon today. In much the same way that one would answer the question of whether he or she is cured of a common cold, the definition of cure depends on the person giving the answer. Luckily, the question of cure of a UV formulation is more definitive.
A UV formulation is designed to do a specific job. A curable formulation, whether it is an ink, an adhesive, a hardcoat, or whatever, is considered to be cured when it meets the requirements of its intended application. Those requirements typically include a minimal performance specification such as a specific hardness target for a hardcoat or a shear hang time with a prescribed load and temperature for an adhesive. In addition, there may also be aging and environmental requirements. If a formulation after exposure fails to meet ALL the minimum requirements of acceptability for it's intended application, then it is not cured.
There are cases where a formulation may fail because it is overexposed to UV energy. As an example, if an uncured adhesive formulation is applied to a backing and a specific level of surface tack is a product requirement, it may be that the tack of the adhesive increases during exposure to an acceptable level but upon further exposure, a drop in tack to an unacceptable level occurs. In this case, the adhesive coating is overcured.