Synthesis And Modification Of UV-curable Phosphorus-containing Epoxy Acrylat

Ultraviolet(UV)curing is considered to be the most effective way to quickly convet solvent-free liquid oligomers into solid polymers with specific physicolchemical and mechanical properties at room temperature.Epoxy acrylate(EA)is one of the most important and widely used reactive oligomers in UV curing systems.Its cured film has high mechanical strength,excellent solvent resistance,chemical resistance,and good adhesion and other characteristics.However,EA has the disadvantages of high viscosity and easy to burn,which limits its application in some specific fields.In order to meet the requirements of EA for low viscosity and flame retardancy in specific fields such as optical fiber and electronic devices,the synthesis of phosphorus-containing(meth)acrylate(BMEP)monomer and the preparation of UV-curing phosphorus-containing epoxy acrylate(PEA)oligomer were studied.First,di[2-(methacryloyloxy)ethyl]phosphate(BMEP)was synthesized using phosphorus oxychloride(POCl3)and 2-hydroxyethyl methacrylate(HEMA)as raw materials.Its molecular chain contains unsaturated double bonds and phosphate functional groups,that is,phosphorus-containing(meth)acrylate monomers,which can have the advantages of both(meth)acrylate monomers and phosphate ester monomers.The effects of reaction temperature,monomer ratio and other factors on BMEP monomer synthesis were studied.The content of BMEP was determined by potentiometric titration,and the structure of BMEP monomer was analyzed by FTIR and 1H NMR.The results show that:at 25～30 ℃,n(POCl3):n(HEMA)is 1:1.9,BMEP monomer with 91.4%purity and 67.1%yield can be obtained.Then,based on the ring-opening esterification reaction of BMEP and bisphenol F epoxy resin,phosphorus-containing epoxy acrylate(PEA)oligomer was prepared.In addition,through the ring-opening esterification reaction of methacrylic acid(MAA)and bisphenol F epoxy resin,ordinary epoxy acrylate(EA)oligomers were prepared.The prepared two kinds of oligomers were evenly mixed with reactive diluent and photo initiator at a certain ratio and cured by UV radiation.Finally,the properties of the two oligomers and cured films were studied through FTIR,viscosity,thermogravimetric and other tests.The results showed that:PEA and EA oligomers were successfully prepared;the viscosity of BMEP monomer was 45.4 mPa·s,the viscosity of PEA oligomer was 3474.0 mPa·s,the viscosity of EA oligomer was 22050.0 mPa·s,the viscosity of the polymer is only 15.8%of the viscosity of the EA oligomer,and the viscosity of the PEA oligomer drops significantly.The effects of the TPGDA and TMPTA diluents on the properties of cured films in UV curing systems were compared.The results show that the cured film prepared with 20wt%TPGDA as the diluent has the best comprehensive performance.The gel rate of PEA and EA films reached 96.1%and 95.3%respectively.The hardness of PEA curing film decreased slightly compared with that of EA curing film,and the adhesion force reached 1 level.The acid resistance and salt tolerance of PEA and EA curing films were good,while the alkali resistance of PEA cured films was poor.The tensile strength and elongation at break of PEA cured film are better than that of EA cured film;the limit oxygen index(LOI)value of PEA cured film is 23.89%,the LOI value of EA cured film is 21.19%,PEA cured film has certain Flame retardant;PEA and EA cured films have different thermal degradation processes.Compared with EA cured films,PEA cured films begin to degrade at lower temperatures,but are thermally stable at higher temperatures.In addition,in order to overcome the shortcomings of PEA cured film brittleness and poor flexibility,the experiment further used polyether urethane acrylate(PUA)to chemically modify PEA,aiming to improve the flexibility of PEA cured film.First,using polytetrahydrofuran ether glycol(PTMG),isophorone diisocyanate(IPDI)and 2-hydroxyethyl methacrylate(HEMA)as raw materials,a partially sealed containing(meth)acrylic unsaturated double bond was prepared.The PUA prepolymer at the end and the terminal-NCO of the PUA prepolymer reacted with the side-OH of the PEA oligomer to prepare a polyurethane acrylate modified phosphoruscontaining epoxy acrylate(PUA-PEA)oligomer.The prepared oligomer,reactive diluent and photoinitiator were uniformly mixed in a certain proportion and UV-cured.Finally,the properties of PUA-PEA oligomer and cured film were studied by FTIR,1H NMR,viscosity,thermogravimetry and other tests.The results show that the viscosity of PUA modified PEA system synthesized with PTMG1000 is moderate,and the introduction of an appropriate amount of PUA has a certain inhibitory effect on the secondary hydrogen bonds formed by the side chain hydroxyl groups of PEA;With the increase of PUA prepolymer content,the tensile strength of the cured film of the PUA-PEA system showed a significant downward trend,while the elongation at break showed a significant upward trend;the flexibility decreased from 15mm to 1mm,the flexibility of the cured film Better;pencil hardness of cured film decreases.The flexibility decreases from 15mm to 1 mm,the flexibility of the cured film is obviously improved;the pencil hardness of the cured film is reduced;the adhesion is around 1 level;SEM analysis shows that the PEA cured film belongs to typical brittle fracture,and with the increase of PUA content,the PUA-PEA cured film shows obvious toughness fracture characteristics;Thermal performance analysis shows that with the introduction of PUA segment before 348.0℃,the heat resistance of PUA-PEA cured film is better than that of PEA cured film,and after the introduction of PUA segment after 348.0℃,the heat resistance of PUA-PEA cured film is inferior to the heat resistance of PEA cured film.PEA and PUA-PEA cured films have a high degree of crosslinking.All cured films have good acid and salt resistance,and PUA-PEA cured films have better alkali resistance than PEA cured films.