Overview
EN ISO 1798:2008 (ISO 1798:2008) specifies a standardized laboratory method for measuring tensile strength and elongation at break of flexible cellular polymeric materials (foams) by extending a test piece at a constant rate until rupture. Published by ISO and endorsed by CEN, this fourth-edition method replaces the 1999 version and adds a second test-piece type for comparative testing.
Key topics and technical requirements
- Scope: Determines maximum tensile stress (tensile strength) and percentage elongation at rupture for flexible cellular polymeric materials.
- Test speed: Power-actuated grips travel at 500 mm/min ± 50 mm/min.
- Test pieces:
- Thickness: 10–15 mm.
- Two cutter types: Type 1 (central width 13 mm; gauge length 25–50 mm typically) and Type 1A (central width 10 mm; gauge length 40 mm).
- Orientation: cut so longitudinal axis is perpendicular to any predominant cell orientation (or report orientation).
- Number: test enough pieces to obtain five valid breaks within the gauge length.
- Conditioning:
- Prepare and condition per ISO 23529.
- Typical conditioning atmospheres: 23 °C ±2 °C/50 % ±5 % RH or 27 °C ±2 °C/65 % ±5 % RH for at least 16 h (with special provisions for time after manufacture).
- Apparatus & calibration:
- Force-measuring system accuracy per ISO 7500-1 (class 0.5 or 1).
- Extensometer (mechanical or optical) if used must meet ISO 9513 accuracy for gauge length.
- Calculations & reporting:
- Tensile strength = maximum force ÷ initial cross-sectional area (based on average thickness and cutter width).
- Elongation at break = (Lbreak − L0) / L0 × 100%.
- Test report must reference the standard and include material type, test-piece type, conditioning details, thickness, median tensile strength and median elongation at break, and any deviations.
Practical applications and users
- Manufacturers of polyurethane and other flexible foams use EN ISO 1798:2008 for product development and specification compliance.
- Quality control laboratories routinely measure tensile properties to verify batch consistency and production changes.
- Independent test labs provide certified material data to OEMs, suppliers, and regulatory bodies.
- Design engineers and product specifiers use these tensile/elongation data when selecting foam for seating, bedding, packaging, insulation, and vibration-damping applications.
- Useful for comparative studies (Type 1 vs Type 1A) and for establishing material acceptance criteria.
Related standards
- ISO 23529 - preparation and conditioning of rubber/foam test pieces
- ISO 7500-1 - verification of force-measuring systems in tensile machines
- ISO 9513 - calibration of extensometers
- ISO 1923 - measurement of linear dimensions for cellular plastics and rubbers
Keywords: EN ISO 1798:2008, tensile strength, elongation at break, flexible cellular polymeric materials, foam testing, polyurethane foam, test piece conditioning, tensile-testing machine.
