Composition cork - Gasket material - Test methods
1Key Takeaways
This document specifies test methods to determine the characteristics of agglomerated composition cork and rubbercork to be used as gaskets in the mechanical industry. The following characteristics are considered: — thickness, — apparent density, — tensile strength, — compressibility and recovery, — flexibility, …
2Expert Interpretation
A comprehensive interpretation of the seven test methods for composite cork and rubber cork gasket materials in the ISO 4708:2017 international standard, including the technical points and implementation specifications for thickness determination, apparent density, tensile strength, compression recovery rate, boiling water resistance, flexibility and fluid resistance tests.
Interpretation of the core content of the standard
ISO 4708:2017 is an international testing standard for composite cork and rubber cork gasket materials used in the machinery industry. Compared with the previous version, the fourth edition mainly deleted the sealing performance test items and strengthened the detection methods of the basic material properties.
Comparison of key test methods
| Test items | Specimen size (mm) | Test conditions | Result expression |
|---|---|---|---|
| Compression recovery rate | 50×50 | 23±5℃/50±5%RH | Percentage change |
| Flexibility (Method A) | 150×15 | Hand bending at room temperature | Minimum crack-free diameter |
| IRM 903 oil resistance | 50×50 | 72h Room Temperature Immersion | Thickness Change (%) |
Technology Evolution Analysis
The 2017 edition of the standard clearly distinguishes for the first time between composite cork (Clause 3.1) and rubber cork (Clause 3.2): the former uses adhesives to bond cork particles, while the latter uses rubber as the base material. This distinction reflects the need for improved standards systems driven by advancements in materials science.
Typical Application Case
When a certain automobile engine gasket manufacturer used clause 7.7.2 of this standard for testing, it was found that after immersion in 100°C ASTM IRM 901 oil for 70 hours, the thickness expansion rate of rubber cork was 15-20% lower than that of traditional composite cork. This provides a quantitative basis for material selection in high-temperature oil seal scenarios.
Implementation Recommendations
- Pretreatment Requirements: All specimens must be conditioned at 23±5℃/50±5%RH for 48 hours (Clause 6.3)
- Dispute Resolution: For the flexibility test, it is recommended to perform both Method A (room temperature) and Method B (aging at 100℃ for 70 hours) simultaneously.
- Safety Warning: 7.7.3 Fuel testing should be conducted in an explosion-proof fume hood because it involves ASTM Fuel A (iso-octane).
Test Report Elements
In accordance with the requirements of Chapter 8, a complete report should include: product type traceability information, sampling plan description (ISO 2859-1 is recommended), original data records for each test item, and any deviation from the standard (such as compression testing of specimens with non-standard thickness).