Study On UV-curable Polyurethane Acrylate Optical Fiber Coatings

Optical fiber communication is inseparable from the protection of optical fiber coatings.High-quality optical fiber coatings must have the characteristics of moderate viscosity,high refractive index,fast curing rate,low water absorption,good mechanical properties,good flexibility,and low glass transition temperature?Tg?.At present,there are few systematic studies on the application of low Tg polyurethane acrylate?PUA?coatings to optical fiber coatings,which is not conducive to the development of high-performance optical fibers.In this project,a low Tg PUA prepolymer was synthesized,its synthesis process was optimized,and an optical fiber coating with excellent performance was formulated with it.Using 2,4-tolylene diisocyanate?TDI?,polypropylene glycol?PPG?,and 2-hydroxyethyl acrylate?HEA?as raw materials,PUA prepolymers were synthesized by chain extension and end-blocking using bulk polymerization,and the synthesis process conditions were optimized:the catalyst dibutyltin dilaurate?DBTDL?mass fraction was 0.1%and the polymerization inhibitor 4-methoxyphenol?MEHQ?mass fraction 0.05%,the reaction temperature in the first step is 50?,and the reaction temperature in the second step is 65?.Fourier transform infrared spectroscopy?FT-IR?and nuclear magnetic resonance proton spectroscopy?¹H-NMR?were used to characterize the structure of the prepolymer,and the structure of the synthesized prepolymer was determined to be in accordance with expectations.The number-average molecular weight of PUA-2000 analyzed by gel permeation chromatography was 2856.The performance analysis of PUA prepolymers shows that:as the relative molecular weight of PPG increases,the viscosity of PUA prepolymers gradually increases,and the curing rate and refractive index gradually decrease,the glass transition temperature of the cured film is gradually reduced,and the flexibility is gradually improved.The effects of 6 reactive polymer thinners with lower Tg of homopolymer,5 photoinitiators and 3 co-initiators on coating properties were investigated.2-[2-[2-[2-?4-nonylphenoxy?ethoxy]ethoxy]ethoxy]ethyl prop-2-enoate[?EO?₄NPA]and isodecyl acrylate?IDA?mass ratio of 2:3 is used as reactive diluent,benzophenone?BP?and 2-hydroxy-2-methylpropiophenone?1173?mass ratio of 1:1 is used as photoinitiator,ethyl 4-dimethylaminobenzoate EDAB is used as a co-initiator.At this time,the obtained coating has excellent comprehensive performance,and the Tg of the cured film is lower than-50°C.Since oxygen has an effect of inhibiting polymerization,which is not conducive to actual production,the anti-oxygen method has been studied.The experiment found that adding thiol to the coating system can effectively inhibit the inhibition of oxygen.When the thiol functionality is increased from 1 to 3,the curing time of the coating is significantly shortened.Using too much addition of 3-functional thiol will cause the coating to be unstable and easy to gel.The optimal addition amount is 0.5%of the total mass of the prepolymer and reactive diluent.The Tg of the self-made optical fiber coating is-50?,which is10?lower than the commercially available coatings,and the other properties are not much different,which meets the use conditions of optical fiber coatings.