Overview
ISO 11752:2000 specifies a standardized method to determine the hardness or compressibility of flexible cellular polymeric materials, specifically moulded and extruded sponge or expanded cellular rubber products. The test measures compression and/or the deformation force on finished parts with a thickness of not less than 3 mm. The procedure supports consistent evaluation for quality control, material comparison and design validation.
Key points:
- Applies to flexible cellular polymeric profiles ≥ 3 mm thick
- Measures compression (mm) and/or test force (N)
- Results are reported as median values
Key Topics
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Principle: Compression produced by a defined force applied perpendicular to the test-piece axis, or the force required to deform the specimen to a defined size, is measured.
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Apparatus: Compression-testing equipment complying with ISO 5893 (grade A) with an indentor covering the entire specimen area and uniform traverse rate between 0.2 mm/s and 0.8 mm/s. Measurement limits in the standard include 0.1 mm for compression and 2% for test force.
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Test pieces: Unless otherwise agreed, test pieces are 50 mm long (representative cross-sections for extruded sections or finished parts). At least three test pieces should be tested.
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Conditioning: Test pieces shall be conditioned, undeflected and undistorted, for at least 16 hours in one of the atmospheres defined in ISO 471: either (23 ± 2) °C / (50 ± 5) % RH or (27 ± 2) °C / (65 ± 5) % RH. Testing should not be carried out less than 72 hours after manufacture unless earlier testing meets the specified stability criterion (mean result within ±10% of the 72 h result).
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Procedure: Measure initial height per ISO 1923. Define zero compression by applying an initial force of 1 N (a lower value may be agreed for very soft materials). Apply the agreed test force or compression (not exceeding 50% of specimen thickness), perform the test within 20 s after applying the initial force, and read results immediately. Do not repeat a test on the same piece within 24 hours.
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Expression of results: Record compression to 0.1 mm and force to 0.1 N; report the median of results.
Applications
This test method is practical for:
- Quality control of sponge and expanded cellular rubber components
- Verifying product performance under compressive loading
- Supporting material selection and design decisions
- Ensuring compliance with contractual and regulatory requirements
Related Standards
- ISO 5893:1993 - Tensile, flexural and compression test equipment (constant rate of traverse)
- ISO 471:1995 - Temperatures, humidities and times for conditioning and testing
- ISO 1923:1981 - Determination of linear dimensions
For compliance, include the standardized test report elements from ISO 11752:2000 (reference, material description, number and length of test pieces, conditioning details, test force/compression, indentor speed, median result, deviations and date of test).