Overview - ISO 1798:2008 (tensile strength & elongation at break)
ISO 1798:2008 specifies a standardized laboratory method for determining the tensile strength and elongation at break of flexible cellular polymeric materials (for example, flexible foams). The method measures strength and deformation by extending a prepared test piece at a constant rate until rupture. The fourth edition (2008) introduces a second test-piece geometry (Type 1A) and includes comparative evaluation of Type 1 vs Type 1A in Annex A.
Key topics and technical requirements
- Scope: Applies to flexible cellular polymeric materials; measures maximum tensile stress (TS) and percentage elongation at break (Eb).
- Test pieces:
- Two cutter geometries: Type 1 and Type 1A (figure-based shapes).
- Thickness: 10–15 mm; rectangular cross-section, with or without skin; no visible defects.
- Sampling orientation: cut with the longitudinal axis at right angles to predominant cell orientation where applicable.
- Conditioning:
- Prepare/condition according to ISO 23529.
- Minimum waiting times after manufacture (typical conditioning atmospheres: 23 °C/50% RH or 27 °C/65% RH).
- Apparatus & test speed:
- Tensile-testing machine with uniform jaw separation at 500 mm/min ± 50 mm/min.
- Force-measurement accuracy conforming to ISO 7500-1 (class 0.5 or 1).
- Optional mechanical or optical extensometer meeting ISO 9513 accuracy for elongation measurements.
- Procedure & calculations:
- Mark gauge length (Type 1: 25–50 mm; Type 1A: up to 40 mm), mount symmetrically, apply preload (≤0.1 kPa or ≤0.5% extension), run test to rupture.
- Calculate tensile strength (kPa) from maximum force and cross-sectional area; calculate elongation at break (%) from initial and break gauge lengths.
- Test report must cite ISO 1798, material type, test-piece type, conditioning details, sampling location, thickness, and median TS and Eb values.
Practical applications & users
- Who uses it: material laboratories, foam manufacturers, quality-control engineers, product designers, and certification bodies.
- Why use it:
- Compare materials and formulations by standardized tensile and elongation metrics.
- Validate production quality and compliance for cushioning, sealing, mattress, automotive and packaging foams.
- Support material selection, R&D and supplier acceptance testing.
Related standards
- ISO 23529 - specimen preparation and conditioning for rubber materials
- ISO 1923 - thickness/linear dimensions of cellular plastics and rubbers
- ISO 7500-1 - verification/calibration of force-measuring systems
- ISO 9513 - calibration of extensometers
Note: Users should observe normal laboratory safety practices and check Annex A for comparative data on Type 1 vs Type 1A test-piece behavior.