Manufacturer · Fashion & Home Accessories
Nylon or polyester thread – in upholstery the choice depends mainly on light. Nylon (polyamide) is slightly stronger and more elastic and is excellent for internal, heavily loaded seams. Polyester withstands sunlight and moisture considerably better and keeps its colour, which is why it is preferred for visible seams, convertibles, boats and outdoor furniture.
The two materials in brief
Polyamide (nylon 6 or 6.6) is a synthetic fibre with very high tenacity and abrasion resistance. In upholstery it is almost always used as a bonded multifilament thread – with a coating that binds the filaments together.
Polyester (PES, PET) is the most widely used synthetic fibre in sewing threads. It is stable to light and moisture, has low shrinkage and holds dye well. In upholstery it is also used as a bonded multifilament thread, and for outdoor products with additional UV stabilisation.
Nylon or polyester thread: a comparison of properties
| Property | Nylon (polyamide) thread | Polyester thread |
|---|---|---|
| Tensile strength at the same thickness | slightly higher | high |
| Elasticity and elongation | higher – the seam "absorbs" shocks | lower – the seam is more stable |
| Abrasion resistance | excellent | very good |
| UV resistance | moderate – loses strength in the sun | good to very good |
| Behaviour with moisture | absorbs a little water, elongates slightly | practically absorbs no water |
| Colour stability | weaker in light | better |
| Typical use | internal seams of seats and furniture | visible seams, dashboards, boats, outdoor products |
When to choose nylon thread
- Internal construction seams on car seats that are not visible and not exposed to light.
- Seams with a lot of flexing – seat side bolsters, piping, armrest corners. The elasticity helps the seam not to break under dynamic load.
- Indoor upholstered furniture – sofas, armchairs and headboards, away from windows.
- Leather and dense materials, where the thread must withstand high tension when the cover is stretched on.
When to choose polyester thread
- Visible decorative seams – the colour stays saturated for longer.
- Dashboards, door tops, the parcel shelf – the most light and heat in the interior.
- Convertibles, boats, campervans, garden furniture – direct sun and moisture.
- Products that get wet and dry repeatedly – polyester does not elongate from water and the seam does not slacken.
- Combined products where the thread must behave the same as the polyester fabric.
Common misconceptions
"Nylon is always stronger"
With new thread – yes, the difference in strength favours polyamide. But a seam is judged after years of use. If the product is in the sun, polyamide loses strength faster, and after a few seasons the polyester seam may be the stronger of the two.
"Polyester is stiff and not suitable for leather"
Bonded polyester thread sews very well on leather and vinyl. It is slightly less elastic, but with the right stitch length and tension the seam stays smooth.
"Fishing line is the same as nylon thread"
Monofilament fishing line is a single thick filament, whereas upholstery thread is multifilament and twisted. Monofilament is stiff, slippery, hard to form loops in the machine and quickly becomes brittle in the sun. It is not a substitute for upholstery thread.
Behaviour when sewing
On the machine the two bonded threads behave similarly, but there are nuances. Polyamide is slightly softer and more elastic, so it is more forgiving of slightly too high tension. Polyester is more stable and gives a straighter, more "technical drawing" decorative seam, but the tension needs to be set more precisely so that the leather does not pucker. With both materials the cone should unwind freely from a stand above the machine.
Can the two threads be combined
Yes, and in automotive upholstery this is common. The internal joining seams are sewn with bonded polyamide and the visible decorative ones with polyester. The only important thing is that within the same seam the top and bobbin threads are of the same material. If the top is polyester and the bobbin polyamide, the two threads will elongate differently under load and moisture, and the seam may pucker or loosen.
You will find selected threads in both materials for seats, steering wheels and dashboards in the threads for the automotive industry group.
Price and stock in the workshop
The price of the thread depends on the material, thickness, coating, UV stabilisation, colour and quantity, so a specific quote requires an inquiry. From a practical point of view, many workshops prefer to keep a smaller number of articles: for example, one polyester thread in two thicknesses for all visible and outdoor seams and one bonded polyamide for the hidden seams. This reduces stock, errors when changing cones and the risk of using the wrong material for an outdoor product.
How to decide quickly: three questions
- Will the seam see sunlight? If yes – polyester. If it is permanently outdoors – UV-stabilised polyester.
- Is the seam visible and does the colour matter? If yes – polyester.
- Is the seam hidden and heavily flexed? If yes – bonded polyamide.
If the answers conflict, choose polyester – it is the more versatile option for upholstery. For clothing threads see sewing threads, and for all types threads.
Upholstery threads from Polkom
Polkom is a Bulgarian manufacturer of sewing accessories, with over 30 years of experience. We offer bonded polyamide and polyester threads for automotive, furniture and marine upholstery in a wide range of colours, shade matching to a sample and fast samples for a test seam. Minimum quantities depend on the article. Send an inquiry via our contact page.
