Overview
ISO 3386-2:1997 specifies a standardized laboratory method to determine the compression stress–strain characteristic of flexible cellular polymeric materials of density greater than 250 kg/m³ (high-density materials). The characteristic quantifies the load-bearing behaviour during a controlled compression test (measured during the fourth loading cycle) and supports quality control, comparative testing and material selection.
Key Topics
- Scope and purpose: Method for compression stress–strain of flexible cellular polymers >250 kg/m³. Not intended as a direct measure of long-term load sustainment.
- Test specimen geometry: Test pieces are right parallelepipeds with square load-bearing faces. Minimum face side: 40 mm, with a shape factor of unity; the width-to-thickness ratio shall be 4:1.
- Preparation: Opposing square faces should be moulded surfaces and edges cut perpendicular to expose cell structure. Thin sheets may be plied-up (identical shapes) provided a minimum of 10 cell diameters is included in the thickness of one ply.
- Conditioning: Samples must not be tested less than 72 h after manufacture and be conditioned immediately before testing for at least 16 h at either:
- 23 °C ± 2 °C and 50 % ± 5 % RH (temperate climates), or
- 27 °C ± 2 °C and 65 % ± 5 % RH (tropical climates).
- Apparatus and settings:
- Compression plate velocity: (5 ± 1) mm/min.
- Compression plate must remain parallel to the base plate and overlap the specimen in all directions; surfaces smooth but not polished.
- Thickness measurement accuracy: ±0.1 mm.
- Force measurement accuracy: ±2 %.
- Test procedure: Compress at the specified rate to the required strain, decompress to the initial thickness, repeat three more times and read the force at the specified strain during the fourth loading cycle. Three test pieces are required.
- Expression of results: Compression stress (CC) in kPa is calculated as CC = 1000 × F / A, where F is force in newtons at the specified strain and A is the area of the load-bearing face in mm².
- Repeat tests: Minimum recovery period between repeats on the same piece is 16 h.
Applications
- Routine quality control of high-density foams and expanded cellular rubbers.
- Comparative testing between batches or different formulations where consistent specimen shape factor is ensured.
- Material selection when compression load-bearing response at specified strains is a design requirement.
Related Standards
- ISO 1923 - determination of linear dimensions for cellular materials (referenced for specimen measurement).
- ISO 2439 - hardness of flexible cellular polymeric materials (indentation technique); distinguishes indentation hardness from compression stress–strain characteristics.
This summary highlights the practical value of ISO 3386-2:1997 for testing, reporting and comparing compression properties of high-density flexible cellular materials. For full procedural detail and normative requirements, consult the complete standard text.
Open preview (PDF)Flexible cellular polymeric materials — Determination of stress-strain characteristics in compression — Part 2: High-density materials
