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Polyester or cotton thread? For most garments, polyester thread is the better choice – it is stronger, hardly shrinks and keeps its colour. Cotton thread is preferable for items made from natural fabrics that are ironed at high temperatures, dyed after sewing or must be made entirely from natural fibres.
Polyester or cotton thread – the main differences
| Criterion | Polyester thread | Cotton thread |
|---|---|---|
| Tensile strength | high | lower at the same thickness |
| Elasticity | moderate, follows the fabric | minimal |
| Shrinkage in washing | practically none | possible if not pre-treated |
| Ironing | tolerates medium temperature | tolerates high temperature |
| Dyeing in the finished garment | does not take up reactive dyes for cotton | dyes together with the fabric |
| Colour and UV fastness | very good | good, more prone to fading |
| Look | from matte (spun) to shiny (filament) | matte, natural |
| Lint in the machine | little | more |
When to choose polyester thread
Polyester is the standard in the garment industry because it solves most practical problems:
- jersey and stretch fabrics – the thread stretches with the fabric and does not break during wear;
- workwear and sportswear – withstands frequent washing, abrasion and sweat;
- synthetic and blended fabrics – the thread and the fabric behave the same way in washing;
- high-speed series sewing – core-spun polyester withstands needle heat;
- outdoor products – better resistance to sunlight and moisture.
The most widespread options are spun polyester for general sewing and core-spun (a polyester core with a wrap) for jeans and loaded seams. Browse the sewing threads in the catalogue.
When cotton thread is the better choice
Cotton has its strengths and in some cases is the only right solution:
- garment dyeing – cotton thread takes up the dye together with the fabric, while polyester stays in its original colour;
- linen and heavy cotton that are ironed at high temperatures – a synthetic thread may deform;
- products with 100% natural composition – in eco and organic collections;
- quilted bedspreads and duvets – traditionally sewn with cotton, because the thread and fabric age in the same way;
- a matte, classic look of the seam on shirts and suits.
Mercerised cotton thread is stronger and has a slight sheen compared with standard cotton thread. You will find more options among the cotton threads.
What about blended solutions?
Core-spun thread with a polyester core and a cotton wrap combines the strength of polyester with the look and ironing behaviour of cotton. It is a frequently used compromise for jeans and shirts. Bear in mind, however, that when a finished garment is dyed, the core will not take up the colour – the effect depends on the density of the wrap, so always do a test.
The effect of thread on the composition label
When declaring composition under Regulation (EU) No 1007/2011 on textile fibre names, the fibres of the product are described, and sewing threads usually do not change the declaration – a polyester thread in a cotton shirt as a rule does not prevent the “100% cotton” label. For decorative threads that are a significant visible part of the product, check the requirements specifically. In eco collections, brands often choose cotton thread because of their own requirements rather than because of the label.
Common mistakes when choosing
- Cotton thread on jersey – the seam breaks when stretched.
- Polyester thread on a garment that will be dyed – the seams stay white or in a different tone.
- Different fibres in the needle and the looper without a test – different shrinkage causes seam puckering.
- A cotton thread that is too fine for a loaded seam – cotton requires a greater thickness for the same strength.
Compatibility with machines and speed
On industrial machines running at thousands of stitches per minute, the needle heats up from friction. Polyester tolerates this well, especially in the core-spun version, and cotton thread also copes without problems because it does not melt. Cotton’s weak point is lint – it builds up around the hook and loopers and requires more frequent cleaning. Filament polyester, on the other hand, is slippery and on older machines sometimes requires fine tension adjustment. If the line sews with both types of thread, train operators to check the tension at every changeover.
How the two threads react to washing and time
With repeated washing at 60 °C and tumble drying, polyester thread keeps its strength and colour almost unchanged. Cotton thread gradually thins and fades at the same rate as the cotton fabric – in vintage-style jeans and workwear this is even sought after as an effect. For products that must look new for years, such as uniforms and hotel textiles, polyester is the safer choice.
Practical advice for production
If the collection includes different fabrics, standardise the main colours in polyester and use cotton only for the styles where it has a real advantage. This reduces stock and the risk of mistakes on the line. With a new fabric, always do a test: seam, washing at 40 or 60 °C, ironing and checking for puckering.
Wholesale threads from Polkom
Polkom offers polyester and cotton threads in a wide colour range for garment factories and brands across Europe. In the threads category you will find the main groups, and our team will help you choose between polyester or cotton threads for the specific style. Send us the fabric and your requirements via the contact page and ask for a sample.
