Overview
ISO 7231:2023 - "Polymeric materials, cellular, flexible - Determination of air flow value at constant pressure‑drop" specifies standardized test methods to measure the air flow value (volume flow rate at a constant pressure differential) of flexible cellular polymeric materials (flexible foams). The standard defines two main approaches:
- Method A - for conventional flexible cellular polymeric materials (types unsuitable for sealing purposes).
- Method B - applicable to all flexible cellular polymeric materials, especially those with low air permeability, with two sub‑methods: B1 (manual measurement) and B2 (automatic measurement).
The principle: impose a specified constant pressure differential across a standard foam specimen and measure the air flow rate required to maintain that differential.
Key topics and technical requirements
- Principle: Air flow that maintains a constant pressure differential across a foam specimen is recorded as the air flow value.
- Apparatus:
- Low-pressure-drop flow meters (accuracy up to ±2 %).
- Manometer (0 Pa to 250 Pa range, ±2 % accuracy; inclined manometer recommended).
- Air supply / suction (compressor, blower or vacuum pump).
- Test chambers and mounting with support open area ≥ 70 %.
- Test piece dimensions: nominal parallelepiped (51.0 ± 0.3) mm × (51.0 ± 0.3) mm × (25.0 ± 0.3) mm; three specimens tested.
- Test conditions: standard laboratory conditions - either (23 ± 2) °C & (50 ± 5) % RH or (27 ± 2) °C & (65 ± 5) % RH.
- Test procedure highlights (Method A):
- Place specimen, ensure air seal, maintain pressure differential of (125 ± 1) Pa on the manometer.
- Read flow in dm3/s; for accuracy use adjacent flow meters and sum readings after 10 s.
- Reporting requirements include reference to ISO 7231:2023, method used, material identification, individual and mean air flow values (dm3/s), specimen thickness/orientation/skin presence, test conditions, deviations and date.
- Note: Both skinned and unskinned specimens can be tested but results are not directly comparable.
Practical applications and users
ISO 7231:2023 is used to:
- Characterize air permeability of flexible cellular polymeric materials and evaluate effects of formulation or process changes on cellular structure.
- Support quality control and batch comparison in foam manufacturing.
- Provide material data for product designers and procurement specifications where air flow/permeability matters (e.g., cushioning, filtration backing, acoustic foams).
- Validate R&D changes, production troubleshooting, and supplier qualification.
Typical users:
- Materials scientists, R&D engineers and product developers.
- Foam and polymeric materials manufacturers.
- Accredited testing laboratories and quality control teams.
- Procurement, compliance and specification engineers.
Related standards
ISO 7231:2023 complements other ISO documents and industry test methods for polymeric foams and material characterization. For implementation and conformity, consult national standards bodies or ISO resources for cross‑references and complementary test standards.
Keywords: ISO 7231:2023, air flow value, flexible cellular polymeric materials, foam testing, method A, method B, B1, B2, pressure differential, flow‑meter, manometer, permeability, quality control.