Overview
ISO 4637:1979 specifies the direct tension method for determining rubber-to-fabric adhesion of rubber-coated fabrics. The method is intended for materials that are substantially uniform in thickness and flat (or sufficiently flexible to remain flat under slight compression). It is particularly useful for materials with very thin rubber coatings that are difficult to evaluate by stripping or peeling tests. Note that results from this direct tension method do not necessarily correlate with stripping or peeling test results.
Key topics and technical requirements
- Scope and limitation: Suitable only for flat, uniform samples; best for very thin rubber layers.
- Test principle: Metal cylinders bonded to opposing faces of a small test piece; tensile load applied along the cylinder axis until separation.
- Specimen size & conditioning:
- Test piece: square, approx. 32 mm lateral dimension.
- Condition specimens for at least 24 h in a standard laboratory atmosphere per ISO 2231; maintain same conditions for comparable tests.
- Apparatus & consumables:
- Tensile testing machine with self-aligning jaws; jaw separation rate 50 ± 5 mm/min; force measurement accuracy ±2%.
- Two metal cylinders (preferably aluminium): 25 ± 0.5 mm diameter, ~50 mm long, flat endsurface with Ra ≤ 0.80 µm (ISO/R 468).
- Ethyl cyanoacrylate adhesive: viscosity 75–100 mPas at 25 °C; minimum bond strength to the metal ~14 MPa (direct tension).
- 600-grit abrasive paper, forceps, jig for cylinder alignment, 1 kg weight for axial load during cure.
- Preparation & procedure:
- Degrease cylinders (trichloroethylene), abrade and clean; degrease test piece (1% ammonium hydroxide in acetone), handle with forceps only.
- Bond cylinders using specified adhesive with controlled application, align in jig, apply weight, allow 16–24 h cure in standard atmosphere.
- Test in tensile machine; record maximum force at failure and inspect failure mode.
- Results & reporting:
- Report force at failure (kilonewtons) as the median of five acceptable tests.
- Record mode of failure as C (cohesive in rubber) or RF (rubber/fabric adhesive failure).
- Include sample details, test method reference (ISO 4637), lab conditions, and date.
Applications and users
- Used by R&D labs, quality control, and manufacturers of rubber-coated fabrics, technical textiles and coated materials to evaluate bond strength where peeling tests are impractical.
- Valuable for procurement/specification, failure analysis, and material development when assessing adhesion of thin rubber layers.
Related standards
- ISO 2231 - standard laboratory atmospheres for conditioning and testing
- ISO/R 468 - surface roughness measurement
- ISO/R 36 - referenced stripping test for comparison (adhesion strength of vulcanized rubbers to textiles)
Keywords: ISO 4637, rubber-to-fabric adhesion, rubber-coated fabrics, direct tension method, adhesion testing, coated fabrics tests.
Open preview (PDF)Rubber-coated fabrics — Determination of rubber-to-fabric adhesion — Direct tension method
