RFQ Today
Certifications: EN 10204 3.1 / 3.2 material test certificates (metallic components), material certificate of conformance (polymer products), and complete export documentation packages.
Nylon 66
(PA66)
A world-class technical reference for EPC contractors, mechanical and piping engineers, procurement heads, and TPI inspection agencies specifying Nylon 66 (Polyamide 66) components — covering polymer chemistry and properties, the critical moisture absorption behaviour unique to nylon, product forms (locknut inserts, washers, tubing, machined components), governing standards, and the QC and documentation discipline required for EPC and industrial project supply.
Key Properties
& Selection Logic
Nylon 66 (Polyamide 66, PA66) is one of the two most widely used engineering thermoplastics in the nylon family, distinguished from Nylon 6 by its polymer synthesis route and offering a favourable balance of mechanical strength, wear resistance, chemical resistance, and elevated-temperature performance for mechanical fastener, tubing, and general engineering component applications.
1.1 — What “Nylon 66” Means
“Nylon 66” (also written PA66, Polyamide 66, or Nylon 6,6) refers to a specific polyamide polymer synthesised from two six-carbon monomers — hexamethylenediamine and adipic acid — condensed through a polymerisation reaction that forms the characteristic amide linkages giving the nylon family its name. The “66” designation reflects the six-carbon chain length of each of the two monomers used in synthesis, distinguishing it from Nylon 6 (PA6), which is synthesised from a single six-carbon monomer (caprolactam) through a different polymerisation route. While PA6 and PA66 share broadly similar general engineering characteristics, PA66 typically offers somewhat higher melting point, higher stiffness, and better elevated-temperature performance, while PA6 offers slightly better impact resistance and easier processing — the specific grade selection between the two is driven by the particular combination of mechanical and thermal requirements for the intended application.
1.2 — Key Engineering Properties
Mechanical Strength and Stiffness
Nylon 66 offers substantially higher tensile strength, stiffness, and impact resistance than most other common engineering thermoplastics — tensile strength typically 75–85 MPa (dry, unfilled) and flexural modulus around 2800–3200 MPa, providing structural rigidity suitable for load-bearing mechanical components, spacers, bushings, and fastener elements without the brittleness of some other engineering polymers.
Wear Resistance and Low Friction
Good inherent wear resistance and a relatively low coefficient of friction against metal surfaces make Nylon 66 well suited to bushing, bearing, and sliding wear applications without requiring supplementary lubrication in many light-to-moderate-load applications — though not matching PTFE’s exceptionally low friction (per RR Hydraulic’s PTFE reference) for the most demanding low-friction requirements.
Chemical Resistance
Good resistance to hydrocarbons, fuels, oils, greases, and many organic solvents — Nylon 66 is widely used in automotive fuel system and lubricant-contact components for this reason. However, nylon is attacked by strong acids and, to varying degrees depending on concentration and temperature, by strong alkalis — chemical compatibility must be verified against the specific process fluid, unlike PTFE’s near-universal chemical inertness.
Electrical Insulation
Good dielectric properties make Nylon 66 a standard material choice for electrical insulating components, cable ties, and applications requiring a non-conductive mechanical element in proximity to electrical systems.
1.3 — Glass-Filled and Reinforced Grades
| Grade | Tensile Strength (Dry, MPa) | Flexural Modulus (MPa) | Heat Deflection Temp (°C) | Typical Application |
|---|---|---|---|---|
| Unfilled (natural) PA66 | 75–85 | 2800–3200 | 75–90 | General-purpose components, nyloc inserts, cable ties, light bushings |
| 15% Glass-filled PA66 | 105–120 | 5500–6500 | 210–230 | Moderate structural load, improved dimensional stability |
| 30% Glass-filled PA66 | 150–180 | 8500–10000 | 240–250 | High-strength structural components, gears, load-bearing brackets |
Glass fibre reinforcement substantially increases strength, stiffness, and heat deflection temperature, but reduces impact resistance and elongation, and increases the material’s abrasiveness against mating metal surfaces in sliding-contact applications — select the reinforcement level based on the specific balance of strength/stiffness vs. toughness/wear-compatibility required.
Washers &
Standards Compliance
Nylon 66 is manufactured into several distinct product forms relevant to EPC and industrial procurement, each governed by a specific dimensional and material standard. Full detail on related fastener standards is available across our standards reference library.
Submit product form, standard, size, and quantity to sales@rrhydraulics.com for a certified offer.
2.1 — Nylon Insert Locknuts (Nyloc)
The most widely recognised Nylon 66 application in fastener supply — a hexagon nut with a moulded or pressed-in Nylon 66 insert ring in the upper section of the internal thread, which is undersized relative to the mating bolt’s major thread diameter. As the bolt is threaded through, it forms/cuts its own mating thread into the nylon insert, creating a prevailing-torque locking action that resists vibration-induced loosening without relying on friction from bolt preload alone — providing effective mechanical locking even at partial preload or on joints subject to vibration where a plain nut might otherwise back off over time. Governed by DIN 985 (metric) and ISO 10511 (the international harmonised standard), with the nut body itself manufactured in steel or stainless steel per the applicable property class, and only the insert ring being Nylon 66.
2.2 — Nylon Tubing (Pneumatic and General Fluid Conveyance)
Nylon 66 (and related nylon 11/12 grades in some flexible tubing formulations) extruded tube is widely used for pneumatic control line, instrument air, and general low-pressure fluid conveyance tubing — governed by DIN 73378 (nylon tubing for automotive and general engineering pneumatic applications) or SAE J844 (thermoplastic air brake and pneumatic tubing) depending on the specific application and regional standard reference. Nylon tubing offers good pressure rating relative to its wall thickness, good chemical resistance to hydraulic and pneumatic system fluids (oils, greases), and reasonable flexibility for routing through machinery and equipment, though with less flexibility than polyurethane tubing alternatives.
2.3 — Washers, Spacers, and Bushings
Nylon 66 flat washers, spacers, and plain bearing bushings for applications requiring electrical insulation between mating components, corrosion isolation (preventing galvanic contact between dissimilar metals), or simple, low-cost wear surfaces in light-duty sliding or rotating applications — machined or injection-moulded to the required dimensions, typically referencing the equivalent metal washer dimensional standard (ISO 7089/7090, DIN 125) for outside diameter and bore compatibility with standard fastener sizes.
2.4 — Governing Standards
DIN 985 / ISO 10511
Governs nylon insert hexagon locknuts — nut body dimensions per the applicable metric hexagon nut standard, with the nylon insert ring dimensions and prevailing torque performance requirements specific to these standards.
DIN 73378 / SAE J844
Governs nylon tubing dimensions, pressure rating, and material requirements for pneumatic and general fluid conveyance applications — the primary dimensional reference standards for nylon tube procurement.
ASTM D4066 — Nylon Injection/Extrusion Material
The primary US material specification for nylon (polyamide) injection moulding and extrusion materials, classifying grades by composition, reinforcement, and key mechanical/thermal properties — the base polymer material specification underlying finished Nylon 66 component manufacture.
ISO 1874 — Polyamide Moulding and Extrusion Materials
The international equivalent classification standard to ASTM D4066, governing polyamide (including PA66) resin material designation and property classification for injection moulding and extrusion applications.
Property Variation
& Design Implications
Nylon 66’s single most distinctive — and most frequently overlooked — engineering characteristic is its hygroscopic (moisture-absorbing) nature: the polymer absorbs ambient moisture from the air over time, and this absorbed moisture significantly and predictably changes the material’s dimensions and mechanical properties.
3.1 — Why Nylon Absorbs Moisture
The amide linkages that define the polyamide (nylon) polymer structure contain polar carbonyl (C=O) and amine (N-H) groups that readily form hydrogen bonds with water molecules — this is the fundamental chemical reason nylon absorbs atmospheric moisture over time, at a rate and to an equilibrium level dependent on ambient relative humidity and temperature. Nylon 66 typically absorbs approximately 1.0–1.5% moisture by weight at 50% relative humidity equilibrium, and up to 2.5–3.5% at full water saturation (complete immersion or 100% RH equilibrium) — this is not a defect or contamination but an inherent, well-characterised, and predictable property of the polymer chemistry that every specifying engineer must account for.
3.2 — Dimensional and Property Effects of Moisture Absorption
| Property | Dry-as-Moulded (DAM) | 50% RH Conditioned | Practical Implication |
|---|---|---|---|
| Tensile strength | ~80–85 MPa | ~55–60 MPa | Design allowable stress should use conditioned data for long-service components |
| Flexural modulus (stiffness) | ~2900–3200 MPa | ~1000–1300 MPa | Deflection under load increases substantially once moisture-equilibrated |
| Impact strength (Izod) | Lower | Higher — moisture acts as a plasticiser, improving toughness | DAM components can be more brittle immediately after manufacture/before equilibrium |
| Dimensional change | Baseline | Typically +0.5–1.0% linear growth at 50% RH equilibrium; up to +2–3% at full saturation | Precision-fit components must account for equilibrium dimensional growth in tolerance design |
3.3 — Design Implications and Best Practice
- Specify design properties at the correct moisture condition: Use moisture-conditioned (typically 50% RH equilibrium) mechanical property data for any component that will spend meaningful service time in a normal ambient environment, rather than DAM data which will overstate stiffness and understate expected deflection
- Account for dimensional growth in precision fits: For close-tolerance nylon components (bushings, precision spacers), calculate the expected dimensional change from DAM to equilibrium moisture content and incorporate this into the tolerance/clearance design — a bushing bore that fits correctly immediately after moulding may bind or seize once the part absorbs moisture and swells in service
- Consider conditioning before critical assembly: For applications where precise, predictable dimensions are critical immediately upon installation, pre-conditioning nylon components to moisture equilibrium (or a specific target moisture content) before final assembly avoids in-service dimensional drift after installation
- Recognise moisture absorption rate depends on part thickness: Thin sections (tubing walls, thin washers) reach moisture equilibrium far faster (days to weeks) than thick sections (large bushings, thick moulded components, which can take months to years) — the practical significance of the DAM-to-equilibrium property shift is more immediately relevant for thin-section parts
- Evaluate glass-filled grades for reduced moisture sensitivity: Glass fibre reinforcement, while not eliminating moisture absorption, reduces its relative dimensional and property impact compared to unfilled nylon, since the glass fibre itself does not absorb moisture and constrains the polymer matrix’s swelling — consider glass-filled grades where dimensional stability across humidity variation is a specific design priority
Industry Applications
& Documentation
RR Hydraulic maintains full traceability and material verification for Nylon 66 component supply, from resin lot through dimensional and mechanical testing to final dispatch documentation.
4.1 — Inspection & QC Protocol
4.2 — Documentation Requirements
| Certificate | Content | EPC Requirement | When Mandatory |
|---|---|---|---|
| Material certificate of conformance | PA66 resin grade, filler content, ASTM D4066/ISO 1874 designation | Mandatory — all EPC supply | All Nylon 66 component supply |
| Dimensional inspection report | Applicable governing product standard tables | Mandatory | All product supply |
| Prevailing torque test report | DIN 985 / ISO 10511 methodology | Mandatory — nyloc insert locknuts | All nylon insert locknut supply |
| Burst pressure test report | DIN 73378 / SAE J844 | Mandatory — pressure-rated tubing | All pneumatic/fluid conveyance tubing supply |
| Moisture condition declaration | DAM vs. conditioned property basis | Conditional — where mechanical property data is provided | Critical or precision-fit applications |
4.3 — Applications by Industry
Vibration-Resistant Fastener Locking
Nylon insert locknuts per DIN 985/ISO 10511 for structural, machinery, and equipment bolted joints subject to vibration where mechanical locking (rather than friction-dependent locking alone) is required to prevent loosening over the joint’s service life — the volume-dominant Nylon 66 application across general industrial and mechanical assembly, limited to service temperatures within the nylon insert’s thermal capability.
Pneumatic and Hydraulic Tubing
Nylon 66 tubing for pneumatic control lines, instrument air distribution, and hydraulic power unit low-pressure circuits — offering good chemical compatibility with hydraulic and pneumatic system fluids, reasonable pressure rating, and cost-effective performance compared to metal tubing alternatives for lower-pressure applications.
Electrical Insulating and Isolation Components
Nylon 66 washers, spacers, and bushings for electrical insulation between components, galvanic isolation between dissimilar metals, and general low-cost wear-surface applications in light-duty mechanical assembly — a straightforward, cost-effective solution wherever a non-conductive, moderately wear-resistant mechanical element is required.
4.4 — Export Packaging Specification
- Nylon 66 components packed in standard cartons with attention to avoiding excessive compressive load on moulded parts during stacking, which could cause permanent deformation particularly in the moisture-conditioned (softer) state
- Where a specific moisture condition (DAM) is critical to the application’s initial fit or performance, components sealed in moisture-barrier packaging (foil-lined bags or sealed containers) to delay moisture equilibration until installation
- Cartons labelled with product type, material grade (unfilled/glass-filled percentage), and applicable dimensional standard, cross-referenced to the accompanying material certificate
- Documentation in a waterproof pocket: material certificate of conformance, dimensional inspection report, prevailing torque test report (nyloc inserts) or burst pressure report (tubing) as applicable, and packing list with product/material/size breakdown per item
- Standard export cartons for international shipment, with country of origin and HS tariff code documentation matched to the nylon product category
Submit your product form, standard, size, and quantity to RR Hydraulic for a complete, certified commercial offer.