Are Zip Ties UV Resistant? Choosing Ties for Outdoor Use

Most zip ties are molded from nylon 6/6. It is tough, inexpensive and holds a ratchet lock well, but unprotected nylon does not like ultraviolet light.

UV radiation carries enough energy to break chemical bonds in the polymer chains. Oxygen then reacts at the broken ends, a process called photo-oxidation. The long chains that give nylon its toughness get shorter, and the material turns hard, weak and brittle. The damage starts at the surface, where the light hits, and works inward.

Heat speeds this up, so ties on dark roofs, metal racking or south- and west-facing surfaces tend to age fastest. A tie under tension also shows damage sooner, because surface cracks open up and grow when the strap is loaded.

Carbon black is a very fine form of carbon mixed into the nylon before molding. It absorbs UV radiation and releases the energy as heat instead of letting it break polymer chains, and it blocks light from reaching deeper into the strap. It is one of the most effective and economical UV stabilizers for plastics, which is why UV-resistant cable ties are almost always black.

Two cautions apply. First, not every black tie is UV-stabilized. A tie can be colored black with a pigment that adds little UV protection, or made with too little carbon black to matter. Second, UV-stabilized does not mean UV-proof. Stabilized ties still age outdoors; they just age much more slowly.

So look for ties that are explicitly described as UV-stabilized, UV resistant or weather resistant, and check the spec sheet when the application matters.

Natural white or clear ties are simply undyed nylon. They are ideal indoors, where their light color is easy to see and they blend with light surfaces, but they have no UV stabilizer. Some manufacturers make UV-stabilized ties in other colors, and those typically offer less protection than carbon-black ties.

There is no honest single number. Outdoor life depends on how intense the sunlight is, which depends on latitude, altitude and orientation, and on heat, tension, wind, moisture and the specific material grade. The same tie can last years longer in shade than on a sunny rooftop.

Supplier estimates for UV-stabilized black nylon ties commonly run to several years, and they vary widely from source to source. Natural nylon ties in full sun can show signs of degradation far sooner. We do not publish a service life for our ties, and nobody can guarantee one for your site, so plan on inspection rather than a fixed replacement date for anything important.

For installations that must last decades without maintenance, or where a specification calls for it, stainless steel ties or engineered clips are often the better fit.

UV damage is usually visible before a tie fails, if you know what to look for.

• Chalky or powdery surface that rubs off on your finger
• Faded color: black turning gray or dull, natural ties turning yellow or cloudy
• Fine surface cracks, especially on the outside of the loop and around the head
• Stiffness: the tail no longer flexes and may snap when bent
• Tails broken off or heads cracked on ties nearby

1. 1Start with the ties that get the most sun and heat, usually on south- and west-facing surfaces and on dark or metal backgrounds.
2. 2Look at each tie for chalking, fading and cracks. Do not flex ties that are holding something important to test them.
3. 3Replace any tie that shows cracking or has turned brittle. If one tie in a run has failed, assume the others of the same age and exposure are close behind.
4. 4Cut old ties carefully with flush cutters so you do not nick cable jackets, hoses or wire insulation.
5. 5Replace with black UV-stabilized ties, sized for the load, and trim tails flush.
6. 6Note the installation date so the next inspection has a reference point.

A few habits make outdoor ties last longer and fail less often.

• Use black UV-stabilized ties for anything that will see daylight, even partial or reflected sun.
• Choose a strength class above what the load needs. Outdoor ties face wind, vibration and temperature swings as well as UV.
• Tighten to snug, not to the limit. Over-tensioned ties are under constant stress, which makes surface cracks grow faster.
• Avoid running ties over sharp metal edges, and use edge protection where you cannot avoid them.
• Check the temperature range on the spec sheet. UV stabilization and heat stabilization are separate properties.
• Where the job specification or equipment manufacturer requires a particular tie, clip or rating, follow it.