GM 9038P is a material standard developed by General Motors, primarily focusing on performance evaluation and testing methods for thermal expansion sealants. Although the standard is not fully public, its core content can be summarized based on industry background and relevant technical documents as follows:
GM 9038P is a material standard developed by General Motors, primarily focusing on performance evaluation and testing methods for thermal expansion sealants. Although the standard is not fully public, its core content can be summarized based on industry background and relevant technical documents as follows:
-
Scope of application
- Material type: Applicable to thermal expansion sealants used in components such as automotive engines, gearboxes, and fuel systems, including dynamic or static seals, gaskets, O-rings, etc.
- Application scenarios: Sealing environments that need to withstand high temperatures, oil fluids (e.g., engine oil, hydraulic oil), fuels (e.g., gasoline, diesel), and chemical media.
-
Core performance requirements
(1) Thermal expansion characteristics- Expansion rate: Within a specific temperature range (e.g., -54°C to 121°C), the sealant must pass thermal expansion tests to ensure it expands to fill gaps at high temperatures and maintains structural stability at low temperatures. For example, a push-rod dilatometer (per ASTM E228) is used to measure the linear thermal expansion coefficient, verifying the material's expansion behavior at different temperatures.
- Cyclic stability: After simulating thermal cycling (e.g., -59°C to 182°C), the material's expansion performance must not exhibit significant degradation to avoid seal failure caused by thermal stress.
(2) Chemical media resistance performance-
Oil resistance test: Must pass liquid immersion tests per ASTM D471 standard, for example:
- IRM 903 oil (simulating engine oil): After immersion at 150°C for 70 hours, volume change ≤±10% and hardness change ≤±10 Shore A.
- ASTM Reference Fuel C (gasoline simulant): After immersion at room temperature for 70 hours, volume change ≤-15% to 0% and tensile strength loss ≤30%.
- Dry shrinkage control: No excessive shrinkage after drying treatment following immersion to prevent fluid leakage through seal gaps.
(3) Physical and mechanical properties- Hardness: Depending on the application grade (e.g., Class B), the hardness range is typically 55-65 Shore A to ensure a tight fit between the seal and the contact surface.
- Tensile strength and tear strength: Must meet specific requirements, e.g., tensile strength ≥10 MPa, to withstand mechanical stresses during installation and operation.
- Low-temperature performance: Pass the flat-bend low-temperature test (e.g., no brittleness or cracking at -59°C) and the compression set test (e.g., deformation ≤70% after 72 hours of compression at -25°C).
(4) Environmental compatibility- Environmental requirements: May restrict the use of harmful substances such as chromates, complying with environmental regulations like RoHS.
- Long-term aging: When simulating environmental factors such as ultraviolet (UV) radiation and ozone, the material's performance must remain stable to avoid cracking or hardening.