A wide variety of irgacure options are available to you, such as free samples. Phenylbis 2,4,6-trimethylbenzoyl phosphine oxide Thick-section curing is also possible with this photoinitiator. Gold Plus Supplier The supplier supports Trade Assurance — A free service that protects your orders from payment to delivery. Are you a distributor irgcure is interested in being listed here?
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There are two types of free-radical generating photoinitiators, designated as Type I and Type II photoinitiators. The highlighted bond in each species undergoes homolytic cleavage upon the absorption of UV light.
Type II photoinitiators require a co-initiator, usually an alcohol or amine, functional groups that can readily have hydrogens abstracted, in addition to the photoinitiator.
The absorption of UV light by a Type-II photoinitiator causes an excited electron state in the photoinitiator that will abstract a hydrogen from the co-initiator, and in the process, splitting a bonding pair of electrons.
An example mechanism is shown in Figure 2. Figure 2. Benzophenone and benzophenone-type photoinitiators are the most common Type II photoinitiators. Once the free-radicals are generated, the polymerization mechanism is no different than any free-radical polymerization process. The chain propagation, termination and transfer steps found in other free-radical processes are consistent in UV polymerization.
Mechanistically, it is only the initiation process to generate free radicals that separates UV polymerization apart. It is this initiation process however that gives UV-curable resins, specifically free-radical UV-curable resins, a very unique advantage over traditional free-radical systems and that advantage is control.
In UV polymerization process you have complete control over the number and rate of free-radicals generated at any point in the process. Free radicals can only be generated upon absorption of UV radiation and the source of UV radiation is defined and controlled by your process an important subject to be discussed in a later post. If you are familiar with thermally-activated free-radical initiators, usually azo or peroxide-based initiators, you will recognize the initiator half-lives as a function of temperature provided by the manufacturer.
This half-life generally indicates the temperature at which half of the initiator molecules split to generate free-radicals with in a specific time period, usually one hour. What this relationship implicitly implies is that at all temperatures free-radicals are generated, with lower rates of generation at low temperatures and higher rates of generation at higher temperatures — generally following the Arrhenius relationship i.
While UV polymerizable resins have specific UV exposure requirements, they do not have pot-lives or freezer storage requirements — they are stable at room temperature in the absence of UV light. In our next post we will discuss the monomeric and oligomeric materials that utilized free-radical photoinitiators.
Photoinitiator 819 | CAS 162881-26-7
JP2016177298A - 液晶ディスプレイ保護板 - Google Patents
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