Appearance: light yellow to amber transparent liquid
Density (25℃):1.000~1.100g/cm 3
Photo initiator (PI) is a key component of photocurable coatings. It is related to whether the oligomer and diluent can quickly change from liquid to solid when the formulation system is irradiated with light, that is, cross-linking and curing. Its basic function is that the initiator molecule has a certain light absorption ability in the ultraviolet light range (250~420nm) or visible light region (400~800nm). After directly or indirectly absorbing light energy, the initiator molecule transitions from the ground state to the active excitation. The singlet state can continue to jump through the intersystem to transition to the excited triplet state. In its excited singlet state, it may also be excited in the triplet state. After undergoing single- or bi-molecular chemistry, active fragments such as free radicals and cations can be generated that can initiate monomer polymerization. Correspondingly, photoinitiators can be divided into free radical polymerization photoinitiators and cationic polymerization photoinitiators. Among them, free radical polymerization photoinitiators are the most widely used, followed by cationic photoinitiators.
The industrial application of photoinitiators can be traced back to the early 1970s, when the photoinitiators at that time were dominated by benzoin ether (benzoin ether) derivatives. At the beginning of the development of light curing technology, styrene was a commonly used light curing monomer, and the benzoin ether photoinitiator was suitable for this kind of strong quenching monomer, so it was widely used at that time, and its use has continued. By the 80s. In addition to benzoin ethers, benzophenone/amine systems and thioxanthone/amine systems were also used at the beginning. These two types of photoinitiator systems are relatively similar and belong to hydrogen abstraction type photoinitiators.
In the middle and late 1970s, benzyl ketal photoinitiators were put on the market, and their appearance greatly promoted the development of the photocurable coating industry. Typical benzyl ketals such as αy dimethyl benzyl ketal (DMB K) ) Up to now, it is still used by some people. It is characterized by strong anti-quenching property, low price, but easy to yellow.
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