In aircraft and automotive fuel tank applications, TPU selection is not based on “fuel resistance” alone. It must be based on a comprehensive evaluation of contact media, temperature range, service life, and safety standards. The key selection parameters are added below.
I. TPU for Aircraft Bladder Fuel Tanks
Application Characteristics
Aircraft bladder fuel tanks require materials that are extremely lightweight, fuel-resistant, low-temperature resistant, antistatic, and flame retardant, and that can minimize fuel leakage and fire risk in a crash. Polyether-based TPU is commonly used, formed into film by hot pressing or extrusion casting and then welded into shape.
Key Selection Parameters
| Parameter | Typical Requirement / Recommended Value | Description |
|---|---|---|
| TPU Type | Polyether-based | Hydrolysis resistant and low-temperature flexible, suitable for high-altitude cold environments |
| Hardness | 80A–90A | Balances flexibility and strength |
| Tensile Strength | ≥ 25 MPa | Ensures pressure resistance and tear resistance |
| Elongation at Break | ≥ 450% | Adapts to wing deformation and impact |
| Tear Strength | ≥ 60 kN/m | Prevents crack propagation |
| Brittleness Temperature | ≤ -50°C | Does not become brittle at low temperatures |
| Fuel Resistance | Tensile strength retention after immersion ≥ 50% | Complies with CTSO-C80 liner strength test |
| Fuel Permeation Rate | ≤ 1 g/m²/day | Reduces fuel loss |
| Hydrolysis Resistance | 70°C/95%RH, 7 days, strength retention ≥ 80% | Advantage of polyether type |
| Surface Resistivity | 10⁶–10⁹ Ω | Antistatic, prevents static charge accumulation |
| Flame Retardancy | Must pass aviation flame retardant tests | Improves safety |
| Density | 1.10–1.20 g/cm³ | Lightweight |
| Processing Method | Hot pressing, extrusion casting, high-frequency welding | Suitable for bladder tank forming |
| Certification Standards | CTSO-C80, FAR 25.853, etc. | Mandatory aviation requirements |
II. TPU for Automotive Fuel Systems
Application Characteristics
In automobiles, TPU is mainly used for fuel line inner layers, fuel tank caps, fuel pump seals, fuel filter housings, and fuel tank liners. It requires gasoline/diesel resistance, low permeation, heat resistance, hydrolysis resistance, and long-term stability.
Key Selection Parameters
| Parameter | Typical Requirement / Recommended Value | Description |
|---|---|---|
| TPU Type | Polyester-based or polyether-based | For pure fuel, choose polyester-based; if moisture may be present, choose polyether-based; multilayer pipes often use a polyester inner layer + polyether outer layer |
| Hardness | 85A–95A | Commonly used for fuel lines |
| Tensile Strength | ≥ 30 MPa | Withstands fuel pressure and vibration |
| Elongation at Break | ≥ 400% | Maintains flexibility |
| Tear Strength | ≥ 80 kN/m | Resists damage during pipe assembly |
| Fuel Volume Swell | ≤ 15% | After immersion in gasoline or diesel |
| Fuel Permeation Rate | < 1 g/m²/day | Meets low-emission requirements |
| Low-Temperature Flexibility | No cracking at -40°C | Used in cold regions |
| Heat Resistance | Long-term 90–120°C | Engine compartment high temperature |
| Hydrolysis Resistance | Polyether type: strength retention ≥ 80% | Prevents degradation in humid environments |
| Density | 1.10–1.25 g/cm³ | Affects weight and cost |
| Melt Flow Index | Adjusted according to extrusion/injection | Extrusion grade requires high melt strength |
| Processing Method | Extrusion, injection molding, multilayer co-extrusion | Fuel lines are often multilayer structures |
| Certification Standards | SAE J30, SAE J2260, DIN 73378 | Automotive fuel system standards |
III. Core Selection Principles
- Aircraft bladder fuel tanks: Prioritize polyether-based TPU, focusing on low-temperature flexibility, fuel resistance retention, antistatic properties, flame retardancy, and CTSO-C80 certification.
- Automotive fuel lines: Prioritize polyester-based TPU (better fuel resistance). If moisture or biodiesel is involved, choose polyether-based or a polyester/polyether composite structure.
- Multilayer structure: Automotive fuel lines often use TPU inner layer + barrier layer + TPU outer layer. The inner layer handles fuel resistance, while the outer layer handles weather and hydrolysis resistance.
- Safety indicators: Aircraft must focus on antistatic and flame retardant properties; automobiles must focus on permeation rate and low-temperature flexibility.
- Processing match: Bladder tanks use hot pressing/welding grade; fuel lines use extrusion grade; seals use injection molding grade.
One-Sentence Summary
For aircraft bladder fuel tanks, choose polyether-based TPU, focusing on low-temperature flexibility, antistatic properties, flame retardancy, and CTSO-C80. For automotive fuel systems, choose polyester-based or polyether-based TPU, focusing on fuel resistance, low permeation, heat resistance, and SAE J30. Hardness, tensile strength, tear strength, fuel resistance retention, permeation rate, and brittleness temperature are the common core selection parameters.
Post time: Sep-28-2026