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5 clicksThe main base materials are PA6, PA66, and PA1012, with a few high-end applications using PA11 or PPA.
It comes in various modified grades including general-purpose, toughened, flame-retardant, weather-resistant, and hydrolysis-resistant types.
These are extrusion-grade specialty compounds and cannot be directly substituted with standard injection-molded nylon.
1.General-purpose at room temperature, cost-effective → Toughened PA6 (main material for automotive wiring harnesses, dominates the market); flame-retardant applications → halogen-free V0 grade.
2.Engine compartment / near motors / requires wear and pressure resistance → PA66 or PA66+GF (heat-stable grade).
3.Near high-temperature heat sources → Toughened PA66.
4.For -40°C operating conditions, do not rely on standard PA6/PA66; even with toughening, long-term reliability is inferior to PA12 or PA1012.
5.New energy battery packs, contact with coolant/electrolyte, extreme cold outdoor environments, low water absorption and dimensional stability → PA12 (use if budget allows; alternatively, use PA1012 as a cost-saving substitute).
II. Key Points for Modifying Polypropylene Tubes
Polypropylene tubes are produced by extrusion molding, and they have much higher requirements for melt strength, toughness, low-temperature impact resistance, and thermal oxidative aging than ordinary injection molded parts.
1. Polypropylene for weather resistance / outdoor use
Add antioxidants + HALS hindered amine light stabilizers; ordinary black carbon black only provides basic weather resistance and will still become brittle under long-term exposure to sunlight; outdoor conditions prioritize PA12, while the life of weather-resistant modified PA6 is limited.
2. Enhancing toughness of polypropylene
PA6/PA66 pure materials are very brittle at low temperatures, so the tubes must be reinforced; POE-g-MAH is commonly used; goal: no cracking after a -30°C drop test / bending; in cold regions, PA12 can be used directly at -40°C, but it is not recommended to forcibly reinforce PA6/PA66 to withstand -40°C; long-term reliability is poor.
3. Flame retardancy of polypropylene
Common: Red phosphorus flame retardant PA6/PA66 (color limited, can only be black)
High-end / new energy: Halogen-free phosphorus-nitrogen type V-0, can be in multiple colors, low smoke, meets automotive / electrical specifications; note that the wall of the tube is thin, and it is necessary to confirm that 0.8/1.0mm can reach V-0; do not just look at the thick sample report.
4. Resistance to hydrolysis (wet heat, dampness, coolant contact)
PA6/PA66 must add hydrolysis stabilizers; humid environments prioritize PA12, which has a low water absorption rate and a low risk of hydrolysis.
5. Color and open-ended polypropylene tubes
Open-ended polypropylene tubes have higher toughness requirements; the material cannot be too hard, otherwise the opening will rebound and crack; black is generally made with high-concentration carrier-free black masterbatch to avoid precipitation and frosting.
III. Selecting formulations based on scenarios
1.For ordinary automotive wiring harnesses (cockpit, doors, chassis): Toughened PA6 + V0 flame-retardant material + main and auxiliary antioxidants → -40 to 125℃, cost-effective.
2.For high-voltage wiring harnesses for new energy vehicles (orange tubes, motors, electronic control units, charging ports): Preferentially use PA12 or water-resistant toughened PA66, with high CTI (≥600V), V0 flame-retardant without halogen, taking into account water resistance and thermal aging. Alternatively, modified PA6/PA66 + V0 + high CTI (≥600V) + oil resistance → long-term at 125℃ or peak at 150℃.
3.For ordinary indoor electrical wiring, machine tools, household appliances, budget should prioritize toughened extruded PA6; for fire protection, select flame-retardant PA6 without halogen (UL94 V‑0).
4.For environments with high temperatures and close to heat sources (around the engine, equipment heat zones), choose toughened extruded PA66; for high temperatures and flame retardancy, select flame-retardant PA66-V0.
5.For 25-year lifespan in solar panels: Modified PA6 + GF + UV-resistant coating + V0, or PA66 thermal-stable grade.
6.For wire protection inside battery packs: PA12 (or PA1012) + V0 + water-resistant, resistant to Li electrolyte, low water absorption, extremely cold flexibility.
7.For outdoor, cold regions, chassis, in contact with engine oil/fuel, requiring repeated bending, -40℃ resistance to cracking, prioritize PA12 or PA1012 extruded grade.
8.For robot drag chains/frequent bending: PA12 toughened or PA6 high resilience toughened, fatigue life priority.
1.Replacing PA66 with PA6 blindly - PA66 is harder, more expensive, and more brittle at low temperatures. The bending radius is larger, and the bellows may not be suitable for use; it is only worth it when the temperature reaches 130℃ or higher.
2.Only asking about "PA bellows" without specifying the brand - PA6 is the original material and modified PA6 V0 at 125℃ are two different things. The "base material + modification + grade" must be locked.
3.Using PA6 for battery packs saves costs - after absorbing water, the insulation resistance drops, and the electrolyte expands when soaked. The after-sales risk is much greater than material quality differences.
4.Using flame-retardant materials with halogen to reduce costs - current vehicle manufacturers and export projects basically require no halogen and low smoke. It cannot be changed later.
5.Ignoring color identification - the orange high-pressure pipe (ISO 6722) is only a color masterbatch and does not represent the temperature resistance. The material still needs to be confirmed separately.
* The application cases shown may not fully match your target products. Please inform us of your specific requirements, and we will assist you in material selection.
