The present invention discloses a fiber surface treatment composition, characterized in that the composition is comprised of a silane coupling agent, a polymer and a water repellent agent, wherein the polymer is a copolymer of a polyurethane/acrylic acid polymer, wherein the acrylic polymer is selected from the group consisting of polyacrylic acid, polyacrylates or acrylic acid-acrylic acid ester copolymers. The invention also discloses an insulating fiber having the composition on its surface, the preparation method for it, and an insulating yarn and an insulated cord. The insulated fibers, yarns and ropes of the invention have the advantages of moisture resistance, washing resistance, ultraviolet aging resistance and the like. Particularly, the insulated ropes can be applied to the charging work of transmission lines, especially the UHV transmission lines.

The present invention discloses a fiber surface treatment composition, characterized in that the composition is comprised of a silane coupling agent, a polymer and a water repellent agent, wherein the polymer is a copolymer of a polyurethane/acrylic acid polymer, wherein the acrylic polymer is selected from the group consisting of polyacrylic acid, polyacrylates or acrylic acid-acrylic acid ester copolymers. The invention also discloses an insulating fiber having the composition on its surface, the preparation method for it, and an insulating yarn and an insulated cord. The insulated fibers, yarns and ropes of the invention have the advantages of moisture resistance, washing resistance, ultraviolet aging resistance and the like. Particularly, the insulated ropes can be applied to the charging work of transmission lines, especially the UHV transmission lines.