Nylon 6 (PA6)
One monomer, one ring-opening step, and an amide group every six carbons. Those amides hydrogen bond to each other, which is where the strength comes from — and they hydrogen bond to water just as readily, which is the complication.
Molecular Structure
What is Nylon 6 (PA6)?
Nylon 6 is made by hydrolytic ring-opening of caprolactam. Unlike Nylon 66, which requires two monomers and a salt-forming step, PA6 needs only one monomer that opens and links head to tail, which makes the process simpler and gives the polymer a lower melting point at 220 °C.
The amide group on every seventh atom is what carries the properties. Amides hydrogen bond strongly to neighbouring chains, producing crystalline domains that give nylon its stiffness, toughness, wear resistance and resistance to hydrocarbons — the reason it displaced metal in so many small mechanical parts.
The same amides bond to water. PA6 takes up around 2.7% moisture at 50% relative humidity and up to 9 or 10% at saturation, and that water acts as a plasticiser: modulus falls, impact strength rises, and dimensions change measurably. Data sheets therefore quote properties both dry-as-moulded and conditioned, and any dimensional design work has to specify which state it refers to.
Nylon 6 must be dried below 0.10% moisture before processing, and the same polymer must usually be conditioned back up to equilibrium moisture afterwards. Those two requirements pull in opposite directions and are frequently confused. Water in the melt hydrolyses the chain permanently; water in the finished part is a designed-for property.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
A six-carbon segment terminated by an amide, repeating head to tail. The amide groups hydrogen bond to their neighbours on adjacent chains, and that hydrogen bonding network is the direct source of nylon's crystallinity, strength and moisture sensitivity alike.
Repeat unit — amide linkage every six carbon atoms
Structural Identity
- PolymerPolyamide 6
- Repeat unit(C₆H₁₁NO)ₙ
- Repeat unit mass113.16 g/mol
- Built fromCaprolactam — a single monomer
- PolymerisationHydrolytic ring opening
- LinkageAmide, head to tail
- Crystal packingAntiparallel chains for full H-bonding
- Molecular weight measureRelative viscosity
- Key vulnerabilityMoisture, in the melt and in service
- CAS Number25038-54-4
- Specified byRV, extractables, moisture, filler
Product Specifications
Chelora supplies Nylon 6 (PA6) in standard and custom grades. Contact us for specification sheets tailored to your process.
| Polymer | Polyamide 6 |
|---|---|
| CAS Number | 25038-54-4 |
| Repeat unit | (C₆H₁₁NO)ₙ |
| Made from | Caprolactam |
| Relative viscosity | 2.4 – 3.4 in 96% sulphuric acid, grade dependent |
| Melting point (DSC) | 220 – 225 °C |
| Density | 1.13 – 1.15 g/cm³ unfilled |
| Tensile strength, dry as moulded | 70 – 85 MPa unfilled |
| Tensile strength, conditioned | 40 – 55 MPa unfilled |
| Notched Izod, conditioned | 50 – 120 J/m unfilled |
| Heat deflection temperature | 60 – 75 °C at 1.8 MPa unfilled; 190 – 210 °C at 30% GF |
| Extractables (max) | ≤ 1.5 wt%; ≤ 0.5% for film and food-contact grades |
| Moisture as supplied (max) | ≤ 0.10 wt% |
| Drying condition | 4 – 6 h at 80 °C under vacuum or dry air |
| Amine end groups | 35 – 55 meq/kg, grade dependent |
| Ash (max) | ≤ 0.10 wt% unfilled |
| Glass fibre grades | 15, 30 and 50% available |
| Food contact | FDA 21 CFR and EU 10/2011 declarations available |
| Transport classification | Not regulated as dangerous goods |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Nylon 6 (PA6).
Textile Filament
The largest global outlet. Partially and fully drawn yarn for apparel, hosiery, swimwear and technical fabric, where PA6 gives better dyeability and a softer handle than PA66.
BCF Carpet Fibre
Bulked continuous filament for residential and contract carpet, usually solution dyed for colourfastness and stain resistance.
Glass-Filled Engineering
30% and 50% glass-filled compounds for automotive components, electrical housings, power tool bodies and structural brackets replacing die-cast metal.
Industrial Yarn
High-tenacity yarn for tyre carcass cord, conveyor belting, ropes, webbing and airbag fabric, where fatigue resistance under repeated flexing governs.
BOPA Barrier Film
Biaxially oriented PA6 film for vacuum and modified-atmosphere food packaging — oxygen barrier, puncture resistance and thermoformability in one layer.
Cast & Machined Stock
Monomer-cast nylon for large gears, rollers, wear pads, sheaves and bushings, produced directly from caprolactam at sizes injection moulding cannot reach.
Why source Nylon 6 (PA6) through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market or off-spec prime passed as prime.
Grade Flexibility
Fibre, film, engineering and glass-filled grades supplied. We match on relative viscosity, extractables and end group balance, because those govern spinning and polymerisation behaviour rather than the headline mechanicals.
Full Documentation
Technical data sheet, CoA including relative viscosity and extractables, SDS, REACH compliance, and food-contact declarations for film and packaging grades.
Logistics Support
Experienced in moisture-sensitive polymer logistics — foil-lined and vacuum-sealed 25 kg bags and jumbo bags, containerised delivery with desiccant, for Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Keep packaging sealed until the moment of use. PA6 picks up moisture from ambient air quickly, and an opened bag left overnight in a humid plant will be off-specification for processing by morning.
- Dry to below 0.10% moisture before processing — typically four to six hours at 80 °C under vacuum or in a dry-air dryer. Water in the melt hydrolyses the amide backbone and lowers relative viscosity permanently.
- Do not confuse drying with conditioning. Drying is a pre-processing requirement; conditioning is deliberately reintroducing moisture into the finished part to bring it to equilibrium properties and dimensions. Both are normal, and each is wrong at the other stage.
- Specify whether design data is dry-as-moulded or conditioned. Modulus and dimensions differ substantially between the two states, and mixing them is a recurring cause of parts that fit at the moulder and not in the field.
- Control melt temperature and residence time. PA6 degrades above roughly 280 °C, and degraded material discolours and loses toughness.
- Use stainless or nitrided surfaces in the melt path. Nylon is mildly corrosive to standard tool steels at processing temperature, and glass-filled grades are abrasive on top of that.
- Expect mould deposit from extractables — residual caprolactam and oligomer migrate to the tool surface and require regular cleaning, more so on low-cost grades with higher extractables.
- Contain pellets rigorously, ground and bond conveying, and control fines, which cause gels in film and specks in moulded parts.
- Treat molten polymer as a serious thermal burn hazard at 240–270 °C, and provide extraction at the die where caprolactam vapour is generated.
Hazard Summary
Classification: polyamide 6 in pellet form is not classified as hazardous under CLP. It is inert and used in food packaging film and food-contact articles. The hazards are process-related.
Hydrolysis in the melt: moisture above about 0.10% cleaves the amide backbone at processing temperature, dropping relative viscosity irreversibly. The moulding or fibre looks acceptable and fails on strength or spins with breaks. Drying is a quality control and, like PET, it fails silently.
Moisture changes properties in service: absorbed water plasticises PA6, lowering modulus and raising impact strength, and swells the part dimensionally. A close-tolerance component designed and measured dry will not hold its dimensions in a humid environment. This is normal and predictable but must be designed for.
Caprolactam vapour and extractables: residual caprolactam monomer and low oligomers migrate out during processing, producing fume at the die and deposit on mould surfaces. Caprolactam is a respiratory and eye irritant, so local extraction at the die is required rather than optional.
Thermal degradation: above roughly 280 °C polyamide 6 degrades, discolouring and releasing ammonia and other decomposition products. Long residence time in a hot barrel produces the same result.
Thermal burns: molten polyamide at 240–270 °C adheres to skin and retains heat. Purging and die work need forearm and face protection.
Abrasion and corrosion of tooling: nylon is mildly corrosive to standard tool steel at melt temperature, and glass-filled grades are highly abrasive. Screw, barrel and tool material selection should reflect the grade being run.
PPE minimum: safety glasses and gloves for pellet handling; heat-resistant gloves, arm protection and face shield for work on molten material, with respiratory protection for any purge event.
Consult the full SDS and the grade technical data sheet for drying and processing conditions, and confirm food-contact status for packaging applications.
Frequently Asked Questions
Technical and commercial questions about Nylon 6 (PA6) sourcing and specifications.
What is Nylon 6 used for?
Textile filament is the largest global outlet — apparel, hosiery, swimwear and technical fabric — followed by bulked continuous filament for carpet. In engineering plastics, glass-filled PA6 replaces metal in automotive components, electrical housings and power tool bodies. High-tenacity industrial yarn goes into tyre cord, conveyor belting, ropes and airbag fabric. Biaxially oriented PA6 film serves vacuum and modified-atmosphere food packaging, and monomer-cast nylon makes large gears and wear parts.
What is the difference between PA6 and PA66?
Chemically, how the amides are arranged. PA6 is built from one monomer that links head to tail, so its amide groups all point the same way along the chain and only align fully when neighbouring chains run antiparallel. PA66 is built from two monomers of even chain length, so its amides align regardless of chain direction and every potential hydrogen bond forms. The practical consequences: PA66 melts around 40 °C higher, is stiffer and holds properties to higher temperature. PA6 processes more easily thanks to the lower melting point and wider window, gives a better surface finish, has somewhat better impact and fatigue resistance, dyes more readily, and absorbs more moisture. Neither is generally better — they are chosen against the specific requirement.
Why does moisture matter so much for Nylon 6?
Because it matters twice, in opposite directions, and the two are easily confused. Before processing, moisture is a defect: water in the melt hydrolyses the amide backbone, cutting molecular weight permanently, so resin must be dried below 0.10%. After processing, moisture is a property: PA6 absorbs around 2.7% water at normal humidity, and that water plasticises the polymer, lowering stiffness, raising toughness and swelling the part. Finished components are often deliberately conditioned to equilibrium so that they reach their in-service properties and dimensions before assembly. Drying the finished part or moulding undried resin are both mistakes, and each is the correct action at the other stage.
What is relative viscosity and why is it used instead of melt flow?
Relative viscosity is the ratio of the viscosity of a dilute nylon solution — usually in 96% sulphuric acid or in formic acid — to that of the solvent alone, and it tracks molecular weight. It is used instead of melt flow index for the same reason intrinsic viscosity is used on PET: nylon hydrolyses and can also continue polymerising in the melt, so a melt-based measurement is not stable enough to characterise the resin reliably. Higher relative viscosity means longer chains, higher melt strength and better mechanical performance, at the cost of harder processing. Fibre grades and film grades occupy different ranges, and the solvent used must always be quoted with the number since the scales are not interchangeable.
What are extractables and why do they matter?
Extractables are residual caprolactam monomer and short oligomers that never entered the polymer chain, typically 0.5 to 1.5% by weight. They matter for three reasons. They migrate to the tool surface during moulding and build up as mould deposit, requiring more frequent cleaning. They volatilise at the die, producing fume that needs extraction. And in food-contact film they are a migration concern, which is why packaging and film grades are specified at 0.5% or below and are washed and dried more thoroughly during manufacture. A cheap grade with high extractables can cost more in downtime than it saves on price.
What documentation does Chelora provide?
Every shipment includes the grade technical data sheet, a Certificate of Analysis covering relative viscosity with the solvent stated, melting point, extractables, moisture content, amine end groups and ash; a Safety Data Sheet to GHS and REACH format; REACH polymer compliance confirmation; food-contact declarations under FDA 21 CFR and EU Regulation 10/2011 for film and packaging grades; an origin certificate; and destination-market certificates where required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Nylon 6 (PA6) grade, volume, logistics, documentation, and lead times. We respond within one business day.
