Manufacturer · Fashion & Home Accessories
UV-resistant threads are synthetic threads that retain their strength and colour with prolonged exposure to sunlight. Most often this is polyester with UV stabilisers and lightfast dyes, and for the harshest outdoor conditions, PTFE (Teflon) thread. They are used for dashboards, the tops of seats, convertible roofs, awnings and boat upholstery.
What the sun does to thread
Ultraviolet rays break the molecular chains in synthetic and natural fibres. The process is gradual and invisible at first. First the colour fades, then the surface of the thread becomes dull and rough, and finally it loses much of its strength and breaks under normal load. The typical picture is a seat or awning where the material looks fine but the seams are falling apart – the thread is thinner than the fabric and takes in light from all sides, so it degrades faster.
A car's glass blocks part of the UV radiation, but not all of it. In addition, behind the glass the dashboard temperature easily exceeds 70–80 °C, and heat accelerates ageing. That is why even visible interior seams need a thread with good light fastness.
Which threads are UV-resistant
Polyester
By nature, polyester withstands sunlight significantly better than polyamide and cotton. For most visible seams in the cabin, a good-quality polyester thread with a lightfast dye is sufficient.
UV-stabilised polyester
UV absorbers and stabilisers are added during the production of the filament or in the coating. Such threads are used for convertible roofs, awnings, tents, boats and garden furniture – wherever the product sits directly in the sun.
PTFE (Teflon) thread
Fluoropolymer thread is practically not degraded by UV rays and chemicals. It is the most expensive option and is used for products that must survive outdoors for many years without replacing the seams – marine awnings, canopies and boat covers.
Polyamide (nylon)
Bonded polyamide is very strong, but with prolonged sun exposure it loses strength faster than polyester. It is excellent for hidden and interior seams, but it is not the first choice for places in direct light.
Comparison of UV-resistant threads
| Thread type | UV resistance | Where it is used |
|---|---|---|
| Cotton | low | not recommended for interiors and outdoor products |
| Polyamide (bonded) | moderate | inner seams of seats, doors, armrests |
| Polyester | good | visible seams in the cabin, steering wheels, seats |
| UV-stabilised polyester | very good | dashboards, convertibles, awnings, boats |
| PTFE | exceptional | marine and permanently outdoor products |
Where in a car UV-resistant thread is needed
- Dashboard – the surface most exposed to the sun, and with the highest temperature.
- Upper door panels and the parcel shelf – they receive direct light through the side and rear windows.
- Tops of backrests and headrests – especially with a panoramic roof.
- Convertible roofs and tonneau covers – they are directly outdoors.
- Steering wheel – receives light through the windscreen every day.
For these areas, choose a thread from the range of threads for the automotive industry, specifying that the seam will be in direct light.
Colour fastness: a separate parameter
Strength and colour do not always go together. A thread may have kept its strength but faded from red to pink. Colour fastness to light is tested by standardised methods (for example the ISO 105 series) and rated on a scale. Dark and neutral colours usually perform better than saturated reds, oranges and yellows, which are favourites for contrast stitching. If you use a bright colour in a convertible, choose UV-stabilised polyester and ask for a sample to compare.
How to tell whether a seam has been damaged by the sun
When inspecting an old seat, awning or convertible roof, look for a few signs. The thread is visibly lighter than the same thread in hidden areas, its surface is dull and fuzzy, and when lightly scratched with a fingernail the fibres fall apart. Another sure sign is when the seam breaks in several places at once while the material around it is intact. In that case there is no point repairing just one spot – the seams in the whole exposed area must be replaced with UV-resistant thread, otherwise the neighbouring sections will soon break too.
How to extend the life of seams
- Use UV-resistant thread only where it is needed, and a more economical bonded polyamide for hidden seams.
- Do not use too fine a thread for outdoor products. A thicker thread has more material and retains its function longer.
- Cover the car or boat when not in use. The cover protects both the material and the seams.
- Clean with products recommended for the material. Aggressive solvents can damage the thread coating.
- Order thread from a single batch for the whole product, so there is no difference in shade that becomes visible after ageing.
UV-resistant threads and clothing
The same principles apply outside the car. For outdoor workwear, beach umbrellas, backpacks and tents, polyester thread is also a better choice than cotton. For ordinary seams in clothing, see sewing threads, and for the full range, all threads.
UV-resistant threads from Polkom
Polkom is a manufacturer and wholesaler of sewing accessories based in Sofia with over 30 years of experience. We supply polyester and UV-stabilised threads for automotive upholstery, convertibles and outdoor products, match colours to a sample and send samples for testing. Minimum quantities depend on the article. Send an inquiry via our contact page and describe where the seam will be working.
