Overview and action mechanism of photoinitiators

2022-02-11 Shanghai Massive Chemical

Although Inmot company of the United States obtained the first patent on UV curing as early as 1946, Bayer Company of Germany industrialized UV curing technology in 1967, thus leading to the concept of photoinitiator, since then the continuous development of photoinitiator. Today, there are a plethora of photoinitiators on the market.

Overview of photoinitiators

Photoinitiator, also known as photosensitizer or photocuring agent, is a kind of compound that can absorb certain wavelength energy in the ultraviolet region (250 ~ 420nm) or visible region (400 ~ 800nm), generate free radicals, cations, etc., thus leading to polymerization of monomers and crosslinking curing.

In the light curing system, including UV glue, UV paint, UV ink and so on, accept or absorb external energy itself chemical changes, decomposition into free radicals or cations, resulting in polymerization reaction. All the light can produce free radicals and further initiate polymerization of substances collectively known as photoinitiator.

Mechanism of action of photoinitiator

Some monomers absorb photons and form excited states M* : M+ hv→M*; The excited active molecules can generate free radicals: M*→R•+R '• through homolysis, and then initiate monomer polymerization to form polymer. Radiation curing technology is a new energy saving and environmental protection technology. UV light, electron beam, infrared light, visible light, laser, chemical fluorescence and other radiation curing, are fully in line with the "5E" characteristics, that is, efficient, practical, economic, energy saving and environmental friendly, therefore known as "green technology".

Photoinitiator is one of the important components of photocuring adhesive, which plays a decisive role in curing rate. After UV irradiation, the photoinitiator absorbs the energy of light and splits into two active free radicals, which leads to chain polymerization of photocurable resin and active diluent, so that the adhesive can be crosslinked and cured. It is characterized by fast, environmental protection and energy saving.