During the manufacturing process of a wire tie, the Nylon 6/6 or other raw material is mixed with carbon black to stabilize the material. Carbon black is a very effective stabilizer and when it is dispersed throughout the material, the wire tie is able to resist being broken down by sunlight or other forms of ultraviolet radiation.
Adding this UV stabilizer prolongs the life of nylon and other plastic materials used outdoors, but does not completely eliminate the destructive effects of this light.
UV stabilization helps a wire tie resist destruction by sunlight, but it does not inhibit its ability to absorb and release moisture. Thus constant exposure to moisture, as well as freezing and thawing, will accelerate break down of the wire tie.