Why is it necessary to add a polymerization inhibitor to light-curing coatings?
In the production process of coatings, some types of coatings contain high polymerization activity of substances, easy to be affected by external factors and polymerization, to light-curing coatings, for example, the main composition of light-curing coatings oligomers and active diluents are high polymerization activity of acrylates, another important composition of photoinitiators and extremely easy to produce free radicals or cations of substances. In such a mixed system, it is very easy to polymerize due to the influence of external light and heat, so it is necessary to add the right amount of polymerization inhibitor. This article introduces the characteristics and applications of polymerization inhibitors for readers.
Polymerization inhibitor is to prevent the occurrence of polymerization of additives. Polymerization inhibitor can terminate all free radicals, so that the polymerization reaction completely stopped. Commonly used polymerization inhibitors are phenols, aromatic amines, aromatic nitro compounds, etc. Oxygen in the air is a good polymerization inhibitor, because oxygen itself is a double radical, very easy to combine with free radicals, generate peroxide radicals, initiation activity is greatly reduced, and finally generate monomer and peroxide bonding alternating oligomers. Light-curing coating polymerization inhibitors are mainly used phenols, such as p-hydroxyanisole, hydroquinone and 2,6-di-tert-butyl-p-cresol. Due to the addition of hydroquinone, sometimes cause the system color darkening, often not used. But phenolic polymerization inhibitors must be in the presence of oxygen to show the polymerization blocking effect.
In the presence of phenolic polymerization inhibitors, so that the peroxide radicals are quickly terminated to ensure that there is sufficient concentration of oxygen in the system, prolonging the blocking time. Therefore, in addition to the addition of phenolic polymerization inhibitors to improve storage stability, we must also pay attention to the storage of the paint in the container can not be too full, to ensure that there is enough oxygen.