Overview
ISO 3386-1:1986 - "Polymeric materials, cellular flexible - Determination of stress‑strain characteristic in compression - Part 1: Low‑density materials" defines a standardized laboratory method to measure the compression stress–strain characteristic and calculate a compression stress value for flexible cellular polymeric materials with density up to 250 kg/m³. The standard quantifies load‑bearing behavior (not long‑term creep performance) using a controlled compression test and prescribes how to report results reproducibly.
Key topics and requirements
- Scope: Low‑density flexible cellular polymeric materials (≤ 250 kg/m³). Part 2 covers high‑density materials.
- Test machine: Uniform vertical motion at 100 ± 20 mm/min; force measurement precision ±2% and thickness measurement precision ±0.2 mm. Autographic recording preferred.
- Test pieces: Right parallelepiped or cylinder, minimum width/diameter : thickness ratio 2:1; preferred thickness 50 ± 1 mm, minimum 10 mm; area ≥ 2 500 mm².
- Support and compression plates: Smooth, flat support surface (may be vented with ~6 mm holes at ~20 mm pitch); compression plate must overlap test piece and be parallel to support surface.
- Conditioning: Do not test sooner than 72 h after manufacture. Immediately before testing condition ≥ 16 h at either:
- Temperate: 23 ± 2 °C, 50 ± 5% RH, or
- Tropical: 27 ± 2 °C, 65 ± 5% RH.
- Procedure: Compress at specified rate until 70% compression or specified strain, decompress to original thickness; repeat three times and record forces on the fourth loading cycle. If multiple strain points are required, measure in increasing strain order without repeating pre‑load between readings.
- Calculations: Compression stress–strain characteristic: stress (kPa) = Fxx / A. Compression stress value at 40%: F40 / A (force in newtons divided by area in mm² - convert units as required).
- Replication and reporting: Test at least three specimens; allow 16 h recovery between repeat tests on same specimen. Report conditioning, specimen dimensions, number of plies (if relevant), individual and median results.
Applications and users
ISO 3386-1 is used by:
- Manufacturers of flexible cellular polymeric materials (rubber and plastics foams) for product specification and quality control
- Independent testing laboratories and R&D teams validating compressive load‑bearing properties
- Product designers and procurement engineers specifying foam for furniture, automotive seating, packaging, footwear, acoustic and cushioning applications
- Standards committees and regulatory bodies referencing reproducible compression test data
Related standards
- ISO 3386-2 - Compression testing for high‑density materials (>250 kg/m³)
- ISO 2439 - Hardness (indentation) for flexible cellular materials
- ISO 1923 - Determination of linear dimensions for cellular materials
Keywords: ISO 3386‑1:1986, polymeric materials, cellular flexible, compression test, stress–strain characteristic, low‑density foam, compression stress value.
