The absorption wavelength of diaryliodonium salts and triarylsulfonium salts is shorter. In order to match the near-ultraviolet light source, some sensitizers are usually added. The free radicals produced by the photolysis of benzoyl peroxide (BPO), anthraquinones, derivatives, a-hydroxyketone, etc. can reduce onium salts and ultimately generate cations and free radicals, respectively triggering cationic and free radical polymerization reactions, increasing photosensitivity. The sensitizer plays an indirect electron transfer role on the onium salt, extending the absorption wavelength and accelerating the curing reaction.
During free radical polymerization, the distance between monomers or oligomers changes from the van der Waals force distance before curing to the distance between covalent bonds after curing, so the volume shrinks significantly, resulting in disadvantages such as large internal stress and poor adhesion. .When epoxy compounds are ring-opening polymerized, on the one hand, the distance between epoxy monomers changes from the van der Waals force distance before curing to the distance between covalent bonds after curing. This process causes volume shrinkage; on the other hand, On the other hand, when the epoxy monomer is polymerized, the size of the structural unit formed by opening the ring on the monomer is larger than the monomer molecule. The overall result of the two is to reduce the volume shrinkage of the ring-opening polymerization reaction of the epoxy compound. Therefore, the size of the epoxy compound Hybrid polymerization consisting of cationic ring-opening polymerization and free radical polymerization of acrylate monomers can control the volume change during curing and reduce the volume shrinkage, thereby reducing internal stress and enhancing adhesion properties.