Fibres · Synthetic
Nylon / Polyamide
The reinforcement fibre par excellence: extremely strong, elastic and light. In knitwear it is almost always used in small doses, to make stockings, cuffs and sock toes last without weighing the garment down.
Translated from Italian. A native knitter has not reviewed this translation yet.
History
It was born in 1935 in the DuPont laboratories at the hands of Wallace Carothers: the first fully synthetic fibre in history, presented to the public in 1938 and launched with the famous stockings of 1940, which turned it into a mass phenomenon. In Europe parallel German research led to Perlon, while in Italy polyamides became a pillar of the twentieth-century chemical and textile district. Since then the trade name has entered everyday language as a synonym for toughness.
How the yarn is made
It is neither shorn nor grown: it is built by chemical synthesis from petroleum derivatives. The monomers are polymerised and then melted, and the liquid polymer is extruded through a spinneret, producing a continuous filament that is cold-drawn to orient its molecules and greatly increase its tenacity. The yarn can remain a shiny flat filament or be textured to give it more bulk and a softer hand; today there are also recycled versions made from fishing nets and industrial waste.
Why it is prized
For a given fineness it is the toughest fibre in the wardrobe, with an elastic recovery no natural fibre can match. A small percentage in a yarn is enough to multiply abrasion resistance where wear comes first, such as sock heels and toes, without reducing stretch or adding weight. It is the classic supporting ingredient: rarely the star, almost always invaluable as reinforcement.
Dyeing
Excellent. Polyamide has amine end groups that bind acid dyes in the same way as wool, giving bright, fast shades. Precisely because of this affinity, in a wool-nylon blend the two fibres can be dyed in a single bath, which helped spread its use in sock yarns.
Care
Very easy to care for: machine washable, resistant to abrasion and tearing, and quick to dry. Wash it in lukewarm water and iron at low temperature, because too much heat makes it pucker and yellow. It tends to build up static and hold odours more than natural fibres; it does not felt and moths leave it alone.
End of life
It is not biodegradable: released into the environment it persists for a very long time and, like all synthetics, sheds microfibres in the wash. It is, however, recyclable: there are supply chains that regenerate it from waste and recovered fishing nets, turning it back into yarn of quality comparable to virgin.
How to recognise it
| Hand | Smooth, cool and slightly slippery to the touch, very light. The yarn gives under tension but snaps straight back, with a sharper elastic recovery than natural fibres. |
|---|---|
| Look | From shiny and silky in the flat filament version to matt and bulky in the textured one; the filament is extremely regular and has no natural crimp, with no halo or fuzz at all. |
| Behaviour | Very elastic and abrasion-resistant, it does not crease and keeps its shape; it is hydrophobic, so it dries quickly but gives little warmth and holds odours. It builds up static easily. |
| Burn test | Synthetic signature: in the flame it melts and shrinks away instead of burning, smelling of celery or hot plastic, and leaves a hard, shiny, greyish bead at the edge of the melt. |
| Home tests | Burn test: the fibre melts into a hard bead, it leaves no crumbly ash · Stretch test: pull and release, the yarn snaps back and does not stay deformed · Water drop: it beads on the surface and is not absorbed, a sign of a hydrophobic fibre |
| Confused with | Polyester: it also melts in the flame, but nylon smells more like celery and takes acid dyes like wool · Elastane/spandex: both are elastic, but spandex recovers from much greater extensions and does not stand up to abrasion in the same way |
| Only in a lab | Telling polyamides from other synthetics with certainty and separating their share in a blended yarn requires laboratory analysis, by selective solubility or spectroscopy (ISO 1833). |
Physical facts
| Property | Value | Source |
|---|---|---|
| elastic memory | High | research |
| sag | Low | research |
| halo | None | research |
| felting risk | None | research |
| fineness (µm) | — | research |
| moisture regain (%) | 4.5 | research |
| typical shrinkage (%) | 0–5 | estimate |
| staple length (mm) | — | research |
measured = a measurement with a reference · iso = a standard · research = a verified source · estimate = plausibility only
For the fabric engine
| friction coefficient (µ) | 0.44 | measured |
|---|---|---|
| density (g/cm³) | 1.14 | measured |
| Young's modulus (GPa) | 2.7 | measured |
| specific bending stiffness (dyn·cm²/tex²) | 0.14 | measured |
Good for
reinforcing stockings and socks · hard-wearing toes and heels · technical and sports garments · durable stretch yarns · hard-wearing accessories
Less good for
warm, airy garments on its own · knitwear that needs to breathe · projects aiming for a natural hand · use near heat sources