PA66 nylon
Selecting PA66 by grade, supplied form, moisture condition and service environment.
Tags: materials, polymers, nylon
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Identity and purchasing scope
BASF Ultramid A3K PA66 at 23°C gives typical tensile modulus 3,000 MPa dry / 1,100 MPa conditioned, and yield stress 85 / 50 MPa at 50 mm/min, by ISO 527-1/-2. Its ISO 179/1eA notched Charpy rises from 5 to 20 kJ/m². Confirm the required conditioning before comparing or specifying a production part. BASF A3K dry and conditioned results
PA66, or nylon 66, is a polyamide supplied both as molding compounds and as stock shapes for machining. A polymer-family name is insufficient to specify a finished component. For example, Ensinger identifies TECAMID 66 natural as an unfilled PA66 stock-shape material; its stock-shape data describe that product rather than every nylon or every molding compound. Record the manufacturer, complete grade, reinforcement or other modification, color, supplied form and applicable product specification. Ensinger: TECAMID 66 natural
Dry and conditioned properties
BASF's Ultramid A3K product information, printed 09/2026, identifies an easy-flowing PA66 injection-molding grade. Its uncolored-material table gives the following typical values at 23 °C in columns labeled “dry” and “cond.” These are characterization values, not universal design allowables. The table does not establish a complete conditioning procedure merely by using that abbreviation. Obtain the applicable protocol before comparing a laboratory result or another supplier's “conditioned” value. BASF: A3K product information
| A3K property and method | Dry | Cond. |
|---|---|---|
| Tensile modulus, ISO 527-1/-2 | 3,000 MPa | 1,100 MPa |
| Yield stress, ISO 527-1/-2, 50 mm/min | 85 MPa | 50 MPa |
| Yield strain, same tensile conditions | 4.5% | 20% |
| Notched Charpy impact strength, ISO 179/1eA, 23 °C | 5 kJ/m² | 20 kJ/m² |
Source: BASF A3K product information, 09/2026.
Worked comparison: 1,100 / 3,000 = 0.367, so the listed conditioned modulus is about 37% of the dry value. This comparison illustrates why stiffness and impact behavior must be considered together; it does not predict a component's deflection, fatigue life or equilibrium moisture content.
Moisture uptake and dimensional control
Ensinger explains that polyamides absorb moisture and change dimensions, and that thick stock can develop a moisture gradient between its surface and interior. Consequently, recording room humidity alone does not prove that a thick part has reached a uniform moisture condition. Ensinger: machinable-plastics FAQ
For a close-fitting bore or sliding component, define when dimensions are accepted: after machining, after a specified conditioning procedure, or under a defined service condition. Include the measurement temperature, elapsed conditioning time and packaging history in the inspection instruction. Test the assembled fit across the intended humidity cycle rather than compensating with an assumed universal swelling percentage.
Water-absorption figures also require their specimen and method. MCAM's 13 February 2024 sheet for Nylatron 101 FG / Ertalon 66 SA FG PA66 stock shapes lists 24-hour uptake at 23 °C as 0.60% under ISO 62 and 0.30% under ASTM D570. Its footnotes specify a 50 mm diameter × 3 mm disc for ISO and a 1/8-inch-thick, 2-inch-diameter or square specimen for ASTM. These separate results do not predict uptake for an arbitrary part. MCAM: named PA66 FG stock-shape data
Processing and machining
Drying resin before molding and conditioning a finished part serve different purposes. BASF's separate A3K processing sheet, also printed 09/2026, recommends a processing moisture content of 0.03–0.06%. It warns that drying duration depends on starting moisture, temperature and dryer dew point, and that excessive drying can increase melt viscosity. Store the grade as instructed, prevent condensation when cold packages enter a warm shop, and keep opened material protected from moisture. These instructions belong to A3K granules, not a general drying schedule for assembled PA66 parts. BASF: A3K processing data
That processing sheet also separates molding shrinkage parallel and normal to flow, listing 1.50% and 1.80% under ISO 294-4. A mold designer should preserve those test conditions and verify the production geometry; neither figure is a machining allowance or a moisture-expansion coefficient. BASF: A3K processing data
For machining stock, Ensinger describes distortion associated with residual stress and asymmetric material removal. Its guidance supports planning intermediate stress relief where appropriate and allowing workpieces to cool before final dimensional assessment. Select any annealing procedure for the actual grade and section rather than applying a generic nylon heat cycle. Ensinger: machining and dimensional-stability FAQ
Temperature, load and chemical exposure
A melting point does not establish a loaded service limit. MCAM's FG sheet bases its long-term air-temperature criterion on approximately 50% tensile-strength loss after at least 20,000 hours, measured at 23 °C, and makes service temperature dependent on load and duration. This does not qualify hot-fluid immersion. MCAM: temperature-rating footnotes
For a bearing, gear or structural spacer, request creep, wear or fatigue evidence appropriate to the contact pressure, speed, mating material, lubrication and temperature. A room-temperature tensile number alone cannot qualify those duties. Likewise, use a thermal-expansion value only over its stated temperature interval and combine thermal and moisture changes in the fit assessment.
DOMO's polyamide chemical-resistance guide explains that strong acids can attack polyamide chains through hydrolysis. Its compatibility tables specify room-temperature conditions, including 23 °C, rather than qualifying every hot exposure. Treat a chart as a screening aid: identify the exact chemical, concentration, temperature, duration, stress and cleaning sequence, then obtain grade-specific evidence or test representative parts. A favorable entry for one liquid cannot establish suitability for a mixture or repeated cleaning cycle. The cited guide does not display a clear publication date; its URL directory is not a revision date. DOMO: engineering-plastics chemical resistance
Minimum specification and qualification record
A useful PA66 purchase and validation record includes:
- Complete grade, supplier, form and modification; approved substitution criteria.
- Property source revision, test method and dry or conditioned state.
- Molding or machining route, relevant section size and conditioning procedure.
- Drawing tolerances with acceptance temperature and moisture condition.
- Sustained load, contact motion, thermal excursions and fluid exposure.
- Representative part tests with explicit acceptance limits and inspection timing.
Retain the distinction between supplier typical data, contractual material requirements and measured finished-part performance. Food-contact, electrical or other regulated suitability requires the exact product documentation and intended-use conditions; the PA66 family name supplies no such approval.