Activators are agents that can increase the activation of other substances. In polymer chemistry, it refers to substances that can easily cleavage the bonds between carbon atoms and heteroatoms in heterocyclic compounds to undergo polymerization or condensation. Commonly used are water, alcohol, acid and alkali. For example, when caprolactam is condensed to polycaprolactam, a small amount of water is added as an activator to split the ring and condense. In the luminescent material, it refers to a trace substance that can cause luminescence. For example, zinc sulfide and cadmium phosphide are used as luminescent pigments, and a small amount of silver or copper can be added as an activator.