Organically modified silicate coatings for optical fibers

Three kinds of UV-curable organically modified silicates have been prepared to be used as protective coatings for optical fibers. The synthesis involves the reaction of the thiol group of 3-mercaptopropyltrimethoxysilane with a C =C bond in one of the acrylic groups of three commercially available aliphatic triacrylates. The methoxysilyl groups of the synthesized diacrylate methoxysilanes were subjected to hydrolysis and condensation to form Si—O—Si units. Transparent, viscous, solvent-free resins were obtained that hardened in seconds when exposed to UV radiation. The coating derived from the reaction with glycerol propoxy triacrylate (GPTA) proved to adhere the best of the three to both plastic and glass substrates. It was then tested as a protective coating for silica fibers. Reliability tests were carried out including bending strength and fatigue tests at pH 7 and 10. The results show improved water resistance of the coated fiber in neutral conditions.