Overview
EN ISO 1856:2018 - Flexible cellular polymeric materials: Determination of compression set specifies test methods to measure the permanent deformation (compression set) of flexible cellular materials. Endorsed by CEN and identical to ISO 1856:2018, it applies specifically to latex and polyurethane foams with thickness greater than 2 mm. The standard defines three methods (A, B and C) for determining compression set and gives requirements for test pieces, apparatus, conditioning, procedure, calculation and reporting.
Key topics and technical requirements
- Scope: Compression set measurement for flexible cellular polymeric materials (latex and polyurethane foams > 2 mm).
- Test methods:
- Method A - Compression at 70 °C: compress to (50 ± 4)% or (75 ± 4)% (90% by agreement), place in oven at (70 ± 1) °C for (22 ± 0.2) h, then allow recovery (30 ± 5) min at conditioning temperature.
- Method B - Compression at standard conditioning temperature: same procedure but maintain compression for (72 ± 0.2) h at conditioning temperature.
- Method C - Custom conditions: time, temperature and compression level agreed between parties.
- Apparatus: Two flat parallel plates with adjustable spacers/clamps; photographic glass slides (1–1.5 mm thick) for thin-material assemblies.
- Test pieces: Typically (50 ± 1) mm × (50 ± 1) mm × (25 ± 1) mm. For thin materials (min 2 mm thickness), assemblies must sum to at least 25 mm; use a minimum of two plies and interleave glass slides as required.
- Number of specimens: Five test pieces (or five assemblies for thin materials).
- Conditioning: Not less than 72 h after manufacture unless 16 h/48 h results are demonstrably within ±10% of 72 h. Condition for at least 16 h at either (23 ± 2) °C / (50 ± 5)% RH or (27 ± 2) °C / (65 ± 5)% RH.
- Calculation: Compression set (%) = ((d0 − dr) / d0) × 100, where d0 = original thickness, dr = recovered thickness.
- Reporting: Include reference to ISO 1856:2018, material description, conditioning, method used, all individual results, median value, test conditions, and deviations.
Applications and who uses this standard
EN ISO 1856:2018 is used by:
- Materials and foam manufacturers for product specification and quality control.
- Independent testing laboratories performing compression-set testing.
- Product designers and specifiers assessing foam performance for cushioning, bedding, seating, insulation and similar applications.
- Procurement and compliance teams requiring standardized test evidence for contracts and regulatory dossiers.
Practical value: provides a repeatable, internationally accepted procedure to quantify permanent deformation after compression - a key property for performance, durability and comfort of flexible foam products.
Related standards
- ISO 1923 - Determination of linear dimensions (used for thickness measurement)
- ISO 23529 - General procedures for preparing and conditioning test pieces for physical test methods
Keywords: EN ISO 1856:2018, ISO 1856, compression set, flexible cellular polymeric materials, latex foam, polyurethane foam, compression test, conditioning, test report.
