ISO 2439:2008

Overview

ISO 2439:2008 - Flexible cellular polymeric materials - Determination of hardness (indentation technique) specifies standardized test methods for measuring the indentation hardness and related load‑bearing properties of open‑cell foams. The standard defines four indentation hardness methods (A–D) and one method (E) to determine the compressive deflection coefficient and hysteresis loss rate. It is applicable to latex foam, urethane foam and PVC foam (open‑cell type) and may be used on standard test pieces or finished articles. Results apply only to the specified test conditions and are not generally suitable for direct design use.

Key topics and technical requirements

• Test methods:
  • Method A: 40% / 30 s indentation hardness index (laboratory measurement).
  • Method B: 25%–40%–65% / 30 s indentation hardness characteristics (curve shape).
  • Method C: 40% indentation hardness check (quick QC test).
  • Method D: 25% / 20 s low indentation hardness index (inspection test).
  • Method E: Compressive deflection coefficient (Sf) and hysteresis loss rate (Af).
• Apparatus & parameters:
  • Indentor: flat circular platen, nominal 200 mm diameter with specified edge radius.
  • Test machine motion: uniform vertical speed of (100 ± 20) mm/min.
  • Force measurement: Class 1 accuracy (ISO 7500‑1) or ±1 N precision; thickness under load to ±0.25 mm.
  • Typical test piece: 380 mm square, (50 ± 2) mm thickness; plied sheets allowed to approximate thickness.
  • Conditioning: specified atmospheres (e.g., 23 ± 2 °C/50 ± 5% RH) and minimum conditioning times before testing.
• Procedure highlights:
  • Preliminary indentations and specified hold times for each method.
  • Autographic recording or tell‑tale needle required for some methods (C, E).
  • Annex A provides typical force‑indentation graphs; Annex B addresses precision of Method E.

Applications

• Characterizing load‑bearing behavior of flexible cellular materials.
• Quality control and production inspection of foam products.
• Comparative material testing for research and development.
• Useful in industries such as bedding, upholstery, automotive interiors, footwear and packaging where foam performance and durability are assessed.

Who should use this standard

• Test laboratories performing physical property testing of foams.
• Quality engineers and R&D teams in foam manufacturing and product development.
• Procurement/specification authors who need standardized hardness data for material selection.

Related standards

• ISO 1382 (Rubber - Vocabulary) - terminology.
• ISO 7500‑1 - verification/calibration of force‑measuring systems.
• ISO 23529 - sample preparation and conditioning procedures.

Keywords: ISO 2439:2008, indentation hardness, flexible cellular polymeric materials, latex foam, urethane foam, PVC foam, compressive deflection coefficient, hysteresis loss, hardness index, indentation technique, foam testing, quality control.