Rubber Products - ASTM D2000-18 Industry Standard

ASTM D2000-18 "Standard Classification System for Rubber Products Used in Automobiles" is a widely adopted material specification in the automotive industry. Its core content establishes a classification system centered on the heat resistance and liquid resistance of vulcanized rubber, and achieves precise description of material properties through standardized test codes. The following is a detailed analysis of its key content:

I. Basic Logic of the Classification System

  1. Classification Dimensions
    Type: Based on heat aging resistance, classified according to the requirements that after aging at a specific temperature for 70 hours, the material’s tensile strength change ≤±30%, elongation change ≤-50%, and hardness change ≤15 Shore A. The specific temperature ranges are as follows:
    • Type A: Test temperature (℃): 70; Typical materials: NR/SBR
    • Type B: Test temperature (℃): 100; Typical materials: CR
    • Type C: Test temperature (℃): 125; Typical materials: EPDM
    • Type D: Test temperature (℃): 150; Typical materials: ACM
    • Type E: Test temperature (℃): 175; Typical materials: FKM
    • Type F: Test temperature (℃): 200; Typical materials: FFKM
    Class: Based on oil swelling resistance, classified by the volume expansion rate after immersion in ASTM Oil No. 3 (or equivalent IRM 903 oil) for 70 hours:
    • Class B: Maximum swelling rate (%): 140; Application scenario: Non-oil-resistant environments
    • Class E: Maximum swelling rate (%): 80; Application scenario: Contact with engine lubricating oil
    • Class H: Maximum swelling rate (%): 30; Application scenario: Fuel systems
    • Class K: Maximum swelling rate (%): 10; Application scenario: Highly corrosive chemicals

II. Core Technical Requirements

  1. Basic Physical Properties
    • Hardness: Tested with a Shore durometer, with a tolerance range of ±5 (e.g., "5" in the marking represents 50±5 Shore A).
    • Tensile strength: The minimum value is indicated by the last two digits in the marking (e.g., "10" represents 10 MPa), which must meet the classification requirements in Table 6.
    • Compression set: For high-temperature applications (e.g., Type D), it must pass ASTM D395 test at 200℃ for 22 hours, with a deformation rate ≤30%.
  2. Environmental Adaptability Tests
    • Heat aging resistance: The test temperature is selected according to the Type grade (e.g., 150℃ for Type D), and the tensile strength change after testing must be ≤±30%.
    • Oil swelling resistance: After immersion in IRM 903 oil, Class E materials must have a volume expansion rate ≤80% and a hardness change ≤15 Shore A.
    • Low-temperature performance: The flexibility of the material at low temperatures is verified by test code F17 (-17℃), such as the TR test in ASTM D1329, which requires a 50% elongation rebound rate ≥10%.
  3. Additional Functional Tests
    • Ozone resistance: The suffix "C" (e.g., C24) indicates testing in 50pphm ozone concentration for 24 hours, requiring no cracks.
    • Fuel resistance: The suffix "EF" (e.g., EF10) corresponds to fuel immersion testing, which requires immersion in ASTM Fuel C for 70 hours with a swelling rate ≤10%.

III. Application Scenarios and Selection Examples

  1. Engine Seals
    • Working conditions: Long-term contact with 150℃ engine oil, requiring oil swelling resistance.
    • Selection:
      • Type D (150℃ heat resistance) + Class E (swelling ≤80%).
      • Test code: M2D514A14EO14 (M: SI unit system; Grade 2; Shore hardness 50±5; tensile strength 14 MPa; heat resistance + oil resistance tests).
  2. Transmission Bushings
    • Working conditions: -40℃ cold start, requiring resistance to transmission oil erosion.
    • Selection:
      • Type B (100℃ heat resistance) + Class H (swelling ≤30%).
      • Test code: M2BH610F17 (-17℃ low-temperature test; Shore hardness 60±5).