Preparation And UV-curing Properties Of Oxazolidine-2-one Based UV Curable Monomers

Photo-curing technology is a green curing technology with"5E"features such as"efficient","economical","environmental friendly","energy saving"and"enabling",which has been applied in many fields.Traditional free radical photo-curing systems face serious oxygen inhibition,resulting in incomplete curing,which in turn affects the performance of the coating.Traditional physical strategies of eliminating oxygen inhibition such as inert-gas protection,film coating and other processes are complex,which is difficult to apply in industrial production.Traditional chemical strategies of eliminating oxygen inhibition such as increasing the photoinitiator and the addition of hydrogen donor can lead to the migration of toxic compounds,yellowing of cured film and reduction of mechanical properties,which limit its practical application.Therefore,the development of new high active,lower oxygen inhibition photo-curing products with high comprehensive performance has important application prospects.This paper reviews some advances in the field of photo-curing research,based on which novel oxazolidin-2-one(OX)based acrylate were designed and synthesized,the photo-curing properties and the physical properties of curing film were evaluated,their application effects in 3D printing were investigated and the polymerization mechanism was proposed.The main contents are as follows.Three novel oxazolidin-2-one based acrylate monomers were synthesized by the aza-Michael addition reaction of OX with 1,6-hexanediol diacrylate(HDDA),1,3-neopentyl glycol diacrylate(NPGDA)and trimethylolpropane triacrylate(TMPTA)catalyzed by potassium carbonate.The reaction progress was traced by FT-IR.The structures and compositions of the products were characterized by ~1H NMR,FT-IR,and ESI-HRMS.The kinetics of the photo-curing process of the OX based acrylate monomers were investigated by FT-IR.The results showed that OX acrylate containing 1 wt%ITX cured faster than tranditional acrylates with 1 wt%ITX and 3 wt%4-(dimethylamino)benzoate(EDB)as co-initiators.In addition,the product of OX with TMPTA with 1 wt%ITX can be UV cured formig film with hardness of 6 H,gel fraction of 99.4%,the shrinkage rate of 11%and the5%thermal weight loss temperature being 314.2°C.The(2-oxazolidin-3-yl)propanoate(OX-MA)was synthesizd by Michael addition reaction of OX with methyl acrylate(MA)catalyzed by potassium carbonate.The OX-MA was selected as model compound with ITX to initiate the UV polymerization.The structure of oligomers extracted from MA photopolymerization products initiated by ITX and OX-MA was investigated by ESI-HRMS.HRMS analysis showed that the oligomer was oxazolidin-2-one-based acrylate triggered polymerization of methyl acrylate,and then terminated by the chain transfer reaction.Based on this point,a plausible polymerization mechanism was proposed.The high photopolymerization activity of OX based acrylate is derived from the effective hydrogen donor capacity of the OX group in the OX based acrylate molecule,which can maintain a high concentration of free radicals in the UV-curing system.Components of the OX with TMPTA with 33 wt%CN996 resin,1 wt%ITX and 1 wt%Da-1173 can be printed into models with light colors and sharp edges by LCD 3D printers.The model has a hardness of 6 H,a gel content of 99.3%,and a 5%weightlessness temperature of 298.4°C.