F66 anti-mildew coating is suitable for coating the interior walls of clean plants, production workshops, warehouses and underground buildings in pharmaceutical, light industry, food, brewery, hospital, kitchen and biological products industries, which are vulnerable to various kinds of mold contamination.
Cationic photoinitiators are another very important type of photoinitiators, including diazonium salts, diaryliodonium salts, triarylsulfuronium salts, alkyl sulfonium salts, iron aromatic hydrocarbon salts, sulfonyloxy ketones and triaromatic Based siloxane ether. Its basic function is characterized by light activation to an excited state, the molecule undergoes a series of decomposition reactions, and finally produces super strong proton acid (also called Bronsted acid) or Lewis acid. The strength of the acid is the key to whether the cationic polymerization can be initiated and proceeded. The acidity is not strong, indicating that the paired anion has strong nucleophilicity and is easy to combine with the carbocation center to prevent chain growth, or polymerization cannot be initiated. Obtain oligomers. Both protic acid and Lewis acid are active species that initiate cationic polymerization. The monomers suitable for cationic photopolymerization mainly include epoxy compounds and vinyl ethers, followed by lactones, acetals, and cyclic ethers.
Compared with free radical photoinitiated polymerization, cationic photopolymerization has the following characteristics:
① As the active species, the protic acid or Lewis acid is chemically stable, and will not couple and disappear like free radicals. It can only be added to the monomer to initiate polymerization and maintain this ionic activity.
②The rate of free radical polymerization is fast, almost not limited by temperature. Once active free radicals are generated: polymerization can be initiated quickly; different from cationic polymerization, it is sometimes necessary to raise the temperature appropriately to accelerate the polymerization at the same time or after light activation.
③ Although free radical photopolymerization is relatively fast, if the light source is suddenly cut off during the process of photopolymerization, the polymerization rate will drop rapidly, and the polymerization conversion rate will still increase slightly, and eventually tend to be constant.
It can be considered that for free radical photopolymerization, the light stops, and the polymerization stops almost immediately; if the light source is suddenly cut off during the cationic photopolymerization process, the polymerization rate does not decrease rapidly, but continues to increase at a faster rate, hs code for hdpe wax and eventually it will also end up through the late dark reaction. A relatively complete polymerization conversion can be achieved. In other words, cationic photopolymerization is immortal polymerization. As long as the light is irradiated, the dark polymerization will proceed smoothly in the later stage.
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