Study On UV-LED Cationic Photopolymerization Kinetics And Preparation Of Organic/Inorganic Hybrid Nanocoatings

As a major innovation,photopolymerization has made great contributions to the economy and ecology in the past few decades.It shows significant advantages in thermal polymerization,including the formation of a polymer network at room temperature,almost free of volatile organic compounds（VOCs）,and good mechanical properties of cured films.In different ways,cationic photopolymerization has attracted people’s attention in recent years due to its oxygen-free polymerization inhibition,cured products with good mechanical properties,and low toxicity and irritation of monomers.However,cationic photoinitiators based on onium salts only absorb short wavelength light（λ<300 nm）and the need for more energy efficient and environmentally friendly UV-LED light sources to replace existing mercury lamps have been an challenge in Rad Tech technique.Furthermore,UV-LED cationic photocurable organic/inorganic hybrid coatings were also prepared.The thesis demonstrated that Si O₂ nanoparticles were synthesized via sol-gel in order to diminish the aggregation of Si O₂nanoparticles as well as to improve its dispersion in organic solvent or polymer matrix.The main researches and conclusions of the thesis are as follows:1.Cationic photopolymerization kinetics of cycloaliphatic diepoxide（CE）and bisphenol A diglycidyl ether（BADGE）have been investigated by real time FTIR under UV-LED light（365 nm）.As a result,with 4.0 wt.%UVI 6976 and1.0 wt.%ITX,the monomer conversion of CE has reached up to 86.1%,the maximum polymerization rate has increased to 2.6 times.Moreover,the initiation system with 8.0 wt.%UVI 6976 and 1.0 wt.%ITX,the monomer conversion of BADGE has reached up to 84.7%,the maximum polymerization rate increased to 1.3 times.The results above also show that the final conversion rate of the epoxy group using UV-LED light（365 nm）as light source system is higher than that of the UV-mercury lamp.2.Cationic photopolymerization kinetics of cycloaliphatic diepoxide（CE）and bisphenol A diglycidyl ether（BADGE）have been investigated by real time FTIR under UV-LED light（405 nm）.The results show that for the CE monomer,the initiation system with ITX and CC has exhibited higher initiation efficiency during the photopolymerization.The initiation system with 8 wt.%Irgacure261 and 0.5 wt.%ITX,the monomer conversion of CE has reached up to 89.5%from 75.4%and the maximum polymerization rate has increased to1.9 times.Moreover,when using the initiation system with 8.0 wt.%Irgacure261 and 1.0 wt.%CC,the monomer conversion of CE has reached up to 88.1%from 75.4%and the maximum polymerization rate has increased to1.7 times for the epoxy system.Besides,the initiation system with 8.0 wt.%Irgacure261 and 1.0 wt.%ITX,the monomer conversion of BADGE has reached up to 81.6%from 60.5%and the maximum polymerization rate has increased to 16 times.3.The thesis demonstrated that Si O₂ nanoparticles were prepared via sol-gel.The feed mole ratios of UV-curing system is TEOS（25）HCl（25）H₂O（25）Et OH（25）A-186=1（25）0.24（25）6.5（25）5.5-6.5（25）0.5-1.The obtained silica sol has a good storage stability in dark at room temperature for more than 180 days.Through the combination of silicone resin and Si O₂ sol,the UV-LED cationic photocurable organic/inorganic hybrid coating was prepared.The coating h as good abrasion resistance,thermal stability and corrosion resistance.