company news about Solve embrittlement and high temperature failure, and overcome the difficulties of epoxy resin curing!

  Ultraviolet light curing (UV curing) of epoxy resins involves the photochemical reaction of photosensitive substances in the system under the influence of ultraviolet light to produce active particles or radicals, thereby initiating cross-linking and polymerization of the active resins in the system. This technology does not require the use of organic solvents and has minimal environmental pollution. It also offers advantages such as fast curing speed, energy conservation, high product performance, and suitability for high-speed automated production lines and coating on heat-sensitive substrates. Currently, commonly used UV curing systems can be divided into free radical curing systems and cationic curing systems based on the different initiation systems.

  Free radical UV curing systems offer fast reaction speeds and easily adjustable properties, but they are sensitive to oxygen, exhibit large shrinkage during photocuring, exhibit poor adhesion, and struggle to fully cure three-dimensional components. Consequently, cationic UV curing has become a hot research and development area in recent years. New hybrid photocuring systems capable of both free radical and cationic photopolymerization are also an active area of ​​research and development. Furthermore, to further expand the application scope of photocuring and improve the performance of photocured products, dual-cure systems combining photocuring with other curing methods are also under continuous research and exploration.

  Cationic photocuring refers to the process in which a cationic initiator generates a proton acid or a Lewis acid under ultraviolet light irradiation, forming a positive ion active center and initiating cationic ring-opening polymerization. Compared with photo-initiated free radical polymerization, cationic curing has the following characteristics: a. It is applicable to a wide variety of monomers. In addition to monomers and prepolymers containing unsaturated double bonds, it is also applicable to a variety of monomers and prepolymers with ring tension, such as acetals, cyclic ethers, epoxides, β-lactones, sulfides and silicones. b. It is not inhibited by oxygen and can achieve rapid and complete polymerization in an air atmosphere, which is conducive to production and practical application. c. It has a post-curing effect, which can shorten the illumination time in practical applications, improve production efficiency and product quality.

  Commonly used sensitizers are free radical photoinitiators such as pyrene, anthracene, and thiazine, or thioxanthenone and xanthone, but the latter two can only be used in combination with iodonium salts. Several triarylsulfonium hexafluoroantimonates were synthesized and used as photoinitiators to investigate factors influencing the cationic photocuring rate of epoxy polymethylsiloxane (EPS) and bisphenol A epoxy resin E-44. The results showed that the structure and concentration of the photoinitiator, as well as sensitizers such as anthracene, phenol, and thiazine, all had varying degrees of influence on the photocuring rate. This method yielded photocurable compositions with fast curing speeds and excellent mechanical properties, exhibiting significant post-curing properties due to active polymerization. These compositions are expected to find applications in high-tech applications such as photocurable coatings, adhesives, sealants, electrical insulation materials, and electronic component packaging.

  In view of the respective characteristics of free radical photocuring and cationic photocuring, the free radical-cationic hybrid photocuring system can complement each other and give full play to the advantages of both, thereby broadening the scope of application of the photocuring system.

  To this end, people have developed a dual-curing system that combines light curing with other curing methods. The cross-linking polymerization of the system is completed through two independent stages with different reaction principles. One stage is through light curing reaction and the other stage is through dark reaction. Dark reaction includes thermal curing, moisture curing, oxidative curing reaction, etc.