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UV coating and composition
UV coatings vary depending on the application area, but the basic dagger is the indigo light, monomer, photoinitiator and additives. UV curing the main reaction process is: caused by radiation-induced photoinitiator decomposition, the formation of active radicals lead monomer or oligomer polymerization cross-linking. Thus, the initiating efficiency of the photoinitiator plays an important role in the cost of the formulation and the rate of light curing, and different curing techniques such as hybrid curing, light and dark curing, etc., also occur around the initiator problem.
1, monomers and oligomers
The main feature of monomers and oligomers is the inclusion of end-group double bonds, which are the basis of photocurable film formation in the research and modification of photocurable film-forming materials. The main idea of its research is: by chemical means, will contain double bond monomer attached to the resin, so that resin has light curing activity.
At present, the acrylic ester is still the most commonly used in the field of light curing oligomers, accounting for 82% of the market; In addition, there are epoxy resin and unsaturated resin two oligomers are commonly used, accounting for 8%. However, conventional photocurable oligomers, such as epoxy acrylate, urethane acrylate, acrylated polyester (or polyether) and unsaturated polyesters, generally have high viscosity, and with the increase of relative molecular weight, Its viscosity also increases, therefore, often need to join the monomer to increase its viscosity. But the monomer will affect the performance of the coating, but also irritating to the skin. In this way, to solve the problem of viscosity of light-cured resin, it has become the focus of light-cured coatings, and the use of hyperbranched polymer is to solve the problem of resin viscosity in one direction. The unique three-dimensional molecular structure of the hyperbranched polymer has the properties of low viscosity, high reactivity and good compatibility, and it also makes the shrinkage of the cured film smaller and thus has good substrate adhesion properties.
2, photoinitiator
Photoinitiator is the core technology of light curing, its performance determines the UV curing coating curing and curing rate. The shortcomings of many light-cured coatings are due to the low efficiency of the photoinitiator or the addition of fillers. In order to meet the growing industrial demand, the development of newer, faster, and unique properties of the photoinitiator has become an important aspect of UV curing technology research. At present, the type of initiator mainly free radical photoinitiator, cationic photoinitiator and so on several.
(1) free radical photoinitiator
Free radical photoinitiators are divided into two types: pyrolysis and hydrogen enrichment.

UV Curing Coatings and Their Prospects