ISO 4708:2017

Overview

ISO 4708:2017 - Composition cork - Gasket material - Test methods - specifies standardized laboratory procedures to determine the physical and performance characteristics of agglomerated composition cork and rubbercork used as gaskets in the mechanical industry. The standard sets out test methods for thickness, apparent density, tensile strength, compressibility and recovery, flexibility (two methods), resistance to boiling water, and behaviour after immersion in specified fluids (ASTM IRM 903 oil, ASTM IRM 901 oil and ASTM Fuel A).

Key topics and technical requirements

• Test scope: Designed for agglomerated composition cork and rubbercork intended for gasket applications.
• Sampling & specimen prep: Sampling follows ISO 2859‑1; specimens cut at least 100 mm from sheet edges and conditioned 48 h at 23 °C (±5 °C) and 50 % (±5 %) RH before testing.
• Specimen sizes: Typical specimen sizes are defined (e.g., compressibility 50 × 50 mm; flexibility 150 × 15 mm). Flexibility test thickness range: 3.2–4.8 mm.
• Apparatus & reagents: Mandrels (8–25 mm diameters), air‑circulation oven (100 ± 2 °C), absorbent paper and containers. Specified reagents include ASTM IRM 903, IRM 901, and ASTM Fuel A (or equivalents meeting Annex A).
• Test procedures:
  • Thickness, density, tensile strength, compressibility/recovery: Referenced procedures and detailed steps are given (ISO 7322 is used for several determinations).
  • Flexibility: Method A - manual flexing over mandrels to find minimum diameter without failure; Method B - thermal ageing (100 °C for 70 h) then flexing. A flexibility factor = (minimum mandrel diameter) / (nominal thickness).
  • Fluid immersion: Specimens immersed for specified times/temperatures; change in thickness reported as percentage: Δd = (d2 − d1) / d1 × 100% (rounded to nearest integer). Volume change for fuels is ΔV = (V2 − V1) / V1 × 100% (rounded to 0.1 %).
• Reporting: Test report must record conditions, specimen details, and numerical results per clause 8.

Applications and who uses it

ISO 4708:2017 is used by:

• Gasket and composition cork manufacturers for product development and quality control.
• Materials and quality laboratories performing routine qualification or acceptance testing.
• OEMs, mechanical designers, and procurement professionals specifying gasket materials for equipment in automotive, industrial machinery, valves and pumps.
• Certification and compliance teams assessing gasket performance in oil/fuel environments.

Practical value: delivers repeatable, comparable test data on compressibility, sealing resilience, thermal and chemical resistance - essential for selecting gasket materials suited to specific mechanical and fluid-service conditions.

Related standards

• ISO 7322 - Composition cork - Test methods (referenced for several determinations).
• ISO 633 - Cork - Vocabulary.
• ISO 2859‑1 - Sampling procedures for inspection by attributes.

Keywords: ISO 4708:2017, composition cork, rubbercork, gasket material, test methods, flexibility test, compressibility, tensile strength, ASTM IRM 903, ASTM IRM 901, ASTM Fuel A.