Research Of UV-Curing Optical Fiber Coatings

As an important component of fiber system, optical fiber coatings play an important role in protecting optical fiber and stabilizing signal transmission. With the expansion of optical fiber application, optical fiber coatings are required of moderate viscosity, fast curing rate, high refractive index, excellent mechanical strength and other properties. Simultaneously, the glass transition temperature of the optical fiber inner coating should be less than-60℃to get low stress at low temperature while the glass transition temperature of the optical fiber outer coating should be higher than 80℃for excellent strength at high temperature. Currently the structure property relation of UV-curing coating, especially the property at high or low temperature, has barely been studied before and the commercial coating products could not well meet the requirement, hindering the development of high-performance optical fiber coating.In present dissertation, excellent UV-curing optical fiber coatings with high or low glass transition temperature were prepared by copolymer molecular designing, oligomer synthesis, and monomer and photoinitiator selection. For developing optical fiber inner coatings, firstly, four polyurethane acrylate (PUA) oligomers of different molecular weight were synthesized with isophorone diisocyanate (IPDI), polypropylene glycol (PPG, Mn is 2000, 4000, 6000, 8000g/mol respectively) and hydroxy ethyl acrylate (HEA). The reaction process was followed by FTIR, and the viscosity and refractive index of the oligomers were measured, and the glass transition temperatures of the cured oligomers were characted by DSC, which are-54．2℃,-60．6℃,-62．0℃and-62．6℃, respectively. Secondly, the influence of the above oligomers and seven soft monomers on coating viscosity, curing rate, refractive index, mechanical strength and glass transition temperature was studied. Finally, the effect of six photoinitiators and two coinitiators on curing rate was investigated.Results showed that optical fiber inner coatings with excellent properties and low glass transition temperature (less than-60℃) were developed with PUA6000 or PUA8000 or their mixture oligomer, with IDA and EO₄NPA as monomers, and Darocur 1173,BP,EDAB as photoinitiators.For developing optical optical fiber outer coatings, based on complextechnology, different properties of oligomers and monomers wereemployed to adjust performance of copolymer and two high glass transitiontemperature oligomers-epoxy acrylate (EA) and polyurethane acrylate(PUA), were selected to investigate its mass ratio on coating properties. In addition, the effect of ten rigid monomers on coating viscosity, cure rate, refractive index, mechanical strength and glass transition temperature was also studied.Results showed that optical fiber outer coatings with excellent properties and high glass transition temperature (more than 80℃) were developed by using EA and PUA as oligomers, NVP, IBOA and DPGDA as monomers, and Darocur 1173,BP,EDAB as photoinitiators.