Effect of polyacrylate binding layers on adhesion of UV-cured epoxyacrylate protective coatings on optical fibers

Polymer coatings on optical fibers were made of homopolymers of methyl methacrylate, poly(butyl acrylate) and poly(nonyl acrylate), the random copolymer of methyl methacrylate with 5% of methacrylic acid and asymmetric block copolymers of the same acrylates with short polar block of poly(5-tert-butyl-peroxy-5-methyl-1-hexen-3-yne-co-maleic anhydride) (50 : 50 mol %). They were obtained by means of physisorption of the polymers from the solution on the surface of two sorts of fused silica rods and plates preliminary heated at 200 and 900°C. The contact angle method was employed to evaluate the structure of adsorbed polymer films in the conditions of poor solvent. The fraction of the silica surface capped by the polymer, and surface free energy and its polar and dispersive components were estimated. The results were correlated with the data of adhesion tests between covered silica rods and ultraviolet (UV)-cured epoxyacrylate and discussed in terms of interpenetration of chains of the preliminary adsorbed polymer and polymer matrix. The chains of binding layer (adsorbed polymer) pull-out from the matrix and pull-off from the substrate failure mechanisms were suggested to explain the adhesion data for different sorts of silica rods. The efficiency of the polymer binding layer increases in the following order: asymmetric block copolymer < copolymer < homopolymer.