What Is Nylon? The First Fully Synthetic Fibre
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Every fibre before 1935 came from a plant, an animal or a chemically modified natural polymer. Nylon was built from coal, air and water, as its marketing claimed with some licence, into a molecule that does not exist in nature, and its arrival demonstrated that useful materials could be designed rather than found, which reoriented the chemical industry permanently.
What it is chemically
Nylon is a polyamide, a long chain built by repeatedly joining two smaller molecules end to end with an amide link, which is the same type of bond that connects amino acids in proteins. That structural resemblance to silk and wool is not accidental, since the research programme was explicitly aimed at understanding and then imitating natural fibres. The most common variety, nylon 6,6, is made from two six-carbon molecules, hexamethylenediamine and adipic acid, with the numbers naming the carbon counts of each component. A closely related variety, nylon 6, is made from a single starting material that opens and joins to itself. The chains pack together in an orderly way and are held to each other by hydrogen bonds between the amide groups, which is what gives the material its strength. Crucially, the polymer is thermoplastic, meaning it melts rather than decomposing, so it can be melted and forced through fine holes in a spinneret to form filaments.
How the fibre is made strong
Extruding a filament is only half the process, and the second half is what creates the properties:
- •Melt spinning forces the molten polymer through a spinneret with many tiny holes, and the emerging filaments solidify in air
- •Cold drawing then stretches the filament to several times its original length, which is the decisive step
- •Drawing aligns the polymer chains along the fibre axis, converting a tangled arrangement into an ordered one in which the strength of the chains themselves is available lengthwise
- •That alignment increases tensile strength several-fold and reduces the stretchiness, which is why undrawn nylon is weak and drawn nylon is not
- •The number and size of the spinneret holes control the fineness of the filament and therefore the feel of the finished textile
- •Additives introduced before spinning provide dullness, ultraviolet resistance, antistatic behaviour and colour, since nylon is otherwise clear and shiny
The launch and the war
Nylon was developed at the DuPont laboratories under Wallace Carothers, who was hired to conduct fundamental research on polymers at a time when the existence of long-chain molecules was still disputed, and whose work established polymer science as a field. The first fibre was drawn in 1935. Carothers died in 1937, before the commercial launch, having suffered from severe depression. Stockings went on sale in 1940 and were an immediate sensation, since nylon was far stronger and cheaper than silk and the supply of Japanese silk was politically fraught. Within two years the entire output was diverted to military use, for parachutes, ropes, tyre cord, tents and flak jackets, and stockings vanished, which produced a black market and the nylon riots when supply resumed after the war. That episode fixed the material in popular memory as a consumer product, while its industrial importance was always larger.
What it became and what it costs
Nylon's properties made it a general-purpose engineering material rather than only a textile. It is tough, resists abrasion, has a low coefficient of friction and self-lubricating behaviour, which is why gears, bearings, bushings and cable ties are made of it, and it resists oils and many solvents. It absorbs water, which is its principal engineering weakness, since dimensions and stiffness change with humidity. Its environmental record is poor on several counts. Production of one of its precursors releases nitrous oxide, a potent greenhouse gas, though abatement equipment has reduced this substantially at modern plants. It does not biodegrade, and discarded fishing nets, which are predominantly nylon, are a major component of marine plastic and continue catching fish for years as ghost gear. Washing nylon textiles releases microfibres into wastewater. Recycling is technically feasible and is being done commercially, particularly with recovered fishing nets depolymerised back to their starting material and respun, which is one of the more genuinely circular processes in the plastics industry.
The takeaway
Nylon is a polyamide whose amide links resemble those in silk and wool, built from small molecules joined end to end, and it was the first fibre made entirely from synthetic components. Melt spinning forms the filament and cold drawing aligns the chains, which is what supplies the strength. Developed under Carothers at DuPont and launched in stockings in 1940, it was diverted entirely to war production within two years. It does not biodegrade, and abandoned nylon fishing nets are a major marine pollutant.