Fibres · Synthetic
Polyester
The most widely used synthetic fibre in the world: practical, strong and colourfast, it holds its shape and dries quickly. In knitwear it is at its best in blends, where it lends strength and lightness to natural fibres.
Translated from Italian. A native knitter has not reviewed this translation yet.
History
It was born in the English laboratories of the Calico Printers' Association at the end of the 1930s and patented in 1941 by Whinfield and Dickson; the first major trade name was Terylene, followed in the United States by Dacron. From the post-war years onwards it conquered clothing and furnishings thanks to its low cost and easy care, until it became the most produced textile fibre on the planet. Today a growing share comes from recycled PET bottles, identified by the label rPET.
How the yarn is made
It is produced by chemical synthesis: molten PET polymer is forced through a spinneret and drawn into a continuous filament (melt spinning). The yarn can remain smooth and shiny, or be heat-textured to give it bulk, stretch and a softer hand; alternatively the filament is cut into staple and spun as if it were a natural fibre, to imitate its hand and make blending easier.
Why it is prized
It is not fine in the noble sense of the word, but it is valuable for practical qualities: it is tough, light, unaffected by moisture and stable to light and washing. In a blended yarn it brings durability and shape retention without adding weight, and keeps colours bright where natural fibres tend to fade.
Dyeing
It is dyed almost only with disperse dyes at high temperature, in an autoclave at around 130 degrees, because the fibre is compact and not very absorbent. Once fixed, however, the colour is among the fastest of all: it withstands sun, washing and rubbing with great consistency.
Care
It is one of the easiest fibres to care for: machine washable at moderate temperature, it dries quickly and does not mind creases. Wash it at low temperatures and away from direct heat, because it melts; with rubbing it can form a few pills, which however tend to come away easily.
End of life
It is not biodegradable and in the environment it breaks down into microplastics, which are released mostly in the wash. It is, however, among the most recyclable synthetics: new fibre is made from PET waste, and pure polyester can be mechanically regenerated or depolymerised to become raw material again.
How to recognise it
| Hand | Smooth and a little slippery, lukewarm or almost neutral to the touch, often slightly drier and more "plasticky" than natural fibres. Textured yarn feels softer and bulkier than smooth yarn. |
|---|---|
| Look | It tends to be shiny and uniform, with full, stable colours. It forms no halo and has no natural crimp: the look is even and lacks the irregularities of natural staple. |
| Behaviour | Very strong and stable: it hardly creases, lies flat again by itself and does not sag under its own weight. It holds little moisture against the skin and dries quickly. |
| Burn test | Synthetic signature: it shrinks away from the flame, melts and drips, burns with black smoke and a sweetish chemical smell, leaving a hard, shiny bead. |
| Home tests | Burn test: melts and drips into a hard bead, leaves no crumbly ash · Touch test: cold or neutral and slippery, without the warmth of wool · Water test: it does not swell and dries much faster than natural fibres |
| Confused with | Nylon, another synthetic that melts: smell and melting point differ, but by eye they are hard to tell apart · Acrylic, another synthetic: it burns more vigorously and leaves a different residue |
| Only in a lab | Telling polyester from other synthetics with certainty and quantifying it in a blend requires laboratory analysis (FTIR spectroscopy, ISO 1833 separation). |
Physical facts
| Property | Value | Source |
|---|---|---|
| elastic memory | Low | research |
| sag | Low | research |
| halo | None | research |
| felting risk | None | research |
| fineness (µm) | — | research |
| moisture regain (%) | 0.4 | research |
| typical shrinkage (%) | 0–3 | estimate |
| staple length (mm) | — | research |
measured = a measurement with a reference · iso = a standard · research = a verified source · estimate = plausibility only
Good for
garments that must hold their shape · blends with natural fibres · sports and technical wear · garments washed often · bright, stable colours
Less good for
next-to-skin wear on its own (poor breathability) · maximum softness and natural warmth · garments that count on biodegradability