Study On The Photopolymerization Process Of Acrylate And The Application In UV Curing Protective Coating Of PCB

In the photopolymerization,the reaction rate is very fast,and the production of free radicals is not affected by temperature.Photopolymerization rate and conversion can be controlled by light intensity.At room temperature,the photopolymerization completed in just a few minutes or even tens of seconds,however the thermal polymerization need to react under a certain temperature conditions for more than three hours and the conversion is hard to be controled.In this study,we investigated the effects of polymerization process on the polymerization process of acrylate monomers,and proposed a method to synthetise UV curing coating that used to protect PCB.The study content mainly includes two aspects:Firstly,we studied the effects of process conditions including monomer types,pendant length,light intensity and photoinitiator on the photopolymerization of acrylate,such as the photopolymerization rates,final conversions,polymer molecular weight and molecular weight distribution.The results show that under the setting polymerization conditions,the final conversion of acrylate was about 85% after polymerizing 250 s and the final conversion of methacrylate was about 15% after polymerizing 450 s.With the increasing of the photoinitiator concentration increased from 0.2% to 1%,the polymerization rate and final conversion of monomer increased,and after increasing the photoinitiator concentration to 1%,both of them were basically unchanged,Mn values were maintained in 31000.Compared with the thermal polymerization,the molecular weight of the photopolymerization was small.Under the same conditions,the Mn and PDI values of photopolymerization were 2.66 and 44340,the Mn and PDI values of thermopolymerization were 101620 and 3.43.We synthesized the acrylic prepolymer by photopolymerization.The protective coating of PCB was prepared by adding crosslinking monomer,photoinitiator and auxiliary agent to the prepolymer.The effects of monomer(including functional monomer),complex photoinitiator and crosslinking monomer on the curing time,pencil hardness,adhesion,water resistance,salt spray resistance and other properties of the coating were investigated.The structure and performance were tested and characterized by FT-IR and simultaneous thermal analyzer(TGA-DSC).