What are the characteristics of photoinitiators? Photoinitiator TPO manufacturers for you to explain

Photoinitiator TPO manufacturers believe that curing technology is a new energy saving and environmental protection technology. Ultraviolet light (UV) is called "green technology" because it fully conforms to the "5E" characteristics. Photoinitiator is one of the most important parts of photocuring adhesive and plays a decisive role in curing speed. After UV irradiation, the photoinitiator absorbs the energy of light and splits into two active free radicals, which leads to the chain polymerization of photosensitive resin and active diluent, so that the adhesive is cross-linked and cured. Its characteristics are fast, environmental protection, energy saving.
Photoinitiator TPO manufacturers believe that the ideal photoinitiator should have the following advantages:

(1) Low price and simple synthesis;

(2) The photoinitiator and its photolysis products should be non-toxic and tasteless;

(3) good stability, easy to preserve for a long time;

(4) The absorption spectrum of the photoinitiator should match the emission band of the radiation source and have a high molar extinction coefficient;

(5) Since most photoinitiators jump to excited singlet state after absorbing light energy, and then jump to excited triplet state through intersystem, the intersystem jump efficiency of photoinitiators is high.

(6) High initiation efficiency.

Photoinitiator TPO manufacturers believe that TPO is a free radical (I) photoinitiator with absorption in the long wavelength range. Due to its wide absorption range, its effective absorption peak is 350-400nm, which has been absorbed to about 420nm. Its absorption peak is longer than that of conventional initiator, and it can produce benzoyl and phosphoacyl radicals, both of which can initiate polymerization. Therefore, the light curing speed is fast, but also has the photobleaching effect, which is suitable for the deep curing of thick film and coating yellowing. It has low volatility and is suitable for water base.

Photoinitiator TPO manufacturers believe that TPO is mostly used in white system, can be used in UV-curable coatings, printing inks, UV-curable adhesives, fiber coatings, photoresist, photopolymerization printing materials, photocurable resins, composite materials, dental fillers, etc. The product should be used according to the actual experimental results, the recommended dosage is 0.5-4.0% W/W, on white or high titanium pigment surface can be completely cured. The coating has no yellowing, low post-polymerization effect and no residue. It can also be used for transparent coating, especially for products with low odor requirements. When used alone in unsaturated polyester system containing styrene, it has higher initiation efficiency. For acrylic systems, especially colored systems, it is usually necessary to use in combination with amines or acrylamide and other photoinitiators to achieve complete curing of the system.

Photoinitiator TPO manufacturers believe that radical polymerization usually includes initiation, chain growth, chain transfer and chain termination. The difference between photoinitiated radical polymerization and traditional thermo-initiated radical polymerization lies in the difference of initiation mechanism. The latter uses thermal initiator decomposition to obtain the active radical while the former uses photoinitiator photolysis reaction to obtain the active radical.

Photoinitiator TPO manufacturers believe that light causes the initiator to change from the ground state to the excited state, and then decompose the free radicals. The radical binds to the carbon-carbon double bond of the monomer, and on this basis, chain growth occurs, resulting in the polymerization of the carbon-carbon double bond. It is also accompanied by free radical transfer and termination in the growing chain.

Photoinitiator TPO manufacturers believe that free radical curing system is a widely used system in photocuring coatings, which has the advantages of fast curing speed and low raw material cost, but there are some problems such as large shrinkage and oxygen resistance, which need to be overcome in the formulation design. In contrast, cationic polymerization uses a post-curing process with small shrinkage and no oxygen inhibition problem, which is now widely used in the 3D printing industry.