Nylon is made from petroleum. Specifically, it starts as crude oil that gets refined into chemical building blocks, which are then linked together through a reaction that produces long, strong polymer chains. The process was first developed at DuPont in 1935, and today about 7 million tonnes of nylon fiber are produced globally each year.
The Raw Materials
Nylon begins its life as benzene, a compound extracted from crude oil during the refining process. That benzene goes through several chemical transformations to become the building blocks, called monomers, that will eventually link up into nylon. The exact monomers depend on the type of nylon being made, but the starting point is always petroleum (with a few newer exceptions covered below).
For the most common variety, nylon 6,6, benzene is first converted into cyclohexane, then oxidized into a mixture of intermediate chemicals, which are further processed using a metal catalyst and nitric acid to produce adipic acid. This is one of nylon’s two key ingredients. The other, hexamethylenediamine, is also derived from petroleum through a separate chain of reactions. About 2.6 million tonnes of adipic acid alone are produced from petroleum each year, and the process releases significant greenhouse gases.
How Monomers Become Nylon
Nylon is formed through a type of reaction called condensation polymerization. Two different monomer molecules join together, and each time they link up, they release a small molecule of water as a byproduct. This happens over and over, building a long chain.
In nylon 6,6, adipic acid reacts with hexamethylenediamine. Each of these molecules contains six carbon atoms, which is where the “6,6” name comes from. Every time one acid molecule bonds with one diamine molecule, a water molecule breaks off, and the chain grows by one unit. The ends of the growing chain still have reactive groups, so the process keeps repeating until the chains reach thousands of units long.
The other major type, nylon 6, works slightly differently. Instead of two separate monomers reacting together, a single monomer called caprolactam opens up its ring-shaped structure and links with other caprolactam molecules in a chain. The result is chemically similar but not identical to nylon 6,6.
Why Nylon Is So Strong
What gives nylon its toughness is the way its molecular chains interact with each other. Along each chain, there are repeating units called amide groups that contain nitrogen, hydrogen, oxygen, and carbon atoms. The hydrogen on one chain is attracted to the oxygen on an adjacent chain, forming what chemists call hydrogen bonds. These bonds act like tiny bridges holding neighboring chains tightly together.
Nylon 6,6 is stronger and has a higher melting point than nylon 6 because of how these hydrogen bonds line up. The nylon 6,6 molecule is symmetrical, which means every available bonding site can pair up with a neighbor. In nylon 6, the molecule is asymmetrical, so only about half of the possible bonding sites actually form hydrogen bonds. This difference in bonding density directly translates to differences in strength, stiffness, and heat resistance.
These hydrogen bonds also encourage the chains to pack into organized, crystalline regions. Nylon is semi-crystalline, meaning parts of it are highly ordered (providing rigidity and strength) while other parts remain loosely arranged (providing flexibility). The balance between these regions determines how the final material behaves.
From Polymer to Fiber
Once the polymerization reaction is complete, the result is a solid material, often formed into small pellets or chips. Turning those pellets into the fibers used in clothing, carpets, and rope requires a process called melt spinning.
The pellets are melted down and forced through a device called a spinneret, which is essentially a plate with tiny holes in it. The molten nylon pushes vertically downward through these holes, emerging as thin filaments. A stream of cool air blows across the filaments to solidify them. The filaments are then gathered together and twisted into thread, treated with a lubricant, and wound onto bobbins. Later, the thread can be drawn (stretched) to align the molecular chains and increase strength, then dyed to the desired color.
Nylon 6 vs. Nylon 6,6
These two types account for the vast majority of nylon production, and the choice between them depends on the application.
- Nylon 6 is made from a single monomer (caprolactam), is slightly more flexible, and is easier to dye. It is commonly used in textiles, packaging films, and industrial yarns.
- Nylon 6,6 is made from two monomers (adipic acid and hexamethylenediamine), has a higher melting point, and is mechanically stronger. It shows up in automotive parts, electrical components, and heavy-duty fabrics.
Nylon 6,6’s denser molecular structure and full hydrogen bonding make it better suited for applications where heat and chemical exposure are concerns. Nylon 6’s simpler production and greater flexibility make it the more versatile textile fiber.
Plant-Based and Recycled Alternatives
Because conventional nylon depends on petroleum and benzene (a known carcinogen), there is growing interest in making nylon from renewable sources. One approach uses sebacic acid, a ten-carbon molecule derived from castor plant oil, to replace the petroleum-based acid component. Combined with other bio-derived monomers, this yields bio-based nylons like PA 5,10 that perform similarly to traditional versions.
Nylon 6 is also particularly well suited to chemical recycling. The polymer chains can be broken back down into caprolactam, which is then re-polymerized into new nylon that is chemically identical to virgin material. Several methods exist for this, including breaking the chains with alkaline solutions, acid solutions, or alcohol-based solvents. Alkaline hydrolysis is currently the most energy-efficient option because the reaction and purification steps integrate cleanly. At production scales of around 12,000 tonnes of recovered caprolactam per year, these recycling processes become profitable within five years.