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Principle and characteristics of photoinitiator

Release time: 2020-12-14

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Principle and characteristics of photoinitiator

  The initiator molecule has a certain light absorption ability in the ultraviolet region (250~400 nm) or visible region (400~800 nm). After directly or indirectly absorbing light energy, the initiator molecule transitions from the ground state to the excited singlet state. Leap to the excited triplet state; after the excited singlet or triplet state undergoes single or bimolecular chemistry, active fragments that can initiate monomer polymerization are generated. These active fragments can be free radicals, cations, anions, etc. According to different initiation mechanisms, photoinitiators can be divided into free radical polymerization photoinitiators and cationic photoinitiators, among which free radical polymerization photoinitiators are more commonly used.

  The ideal photoinitiator should have the following advantages:

  (1) Cheap and easy to synthesize;

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

  (3) Good stability, convenient for long-term storage;

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

  (5) Since most photoinitiator molecules absorb light energy and then transition to an excited singlet state, and jump to an excited triplet state through intersystems, therefore, the intersystem jump efficiency of the initiator is higher;

  (6) Higher initiation efficiency.