Overview
ISO 7389:2002 specifies a standardized laboratory method to determine the elastic recovery of sealants used in building construction jointing products. The test quantifies how well a sealant returns toward its original dimension after being held at a specified elongation, providing an objective measure of sealant elasticity after sustained extension.
Key Topics and Requirements
- Scope: Applies to jointing products (sealants); measures elastic recovery after maintained extension.
- Test principle: Extend the sealant, hold the extension for 24 hours, release and measure dimensional recovery after 1 hour.
- Specimens and substrates: Test specimens are prepared on substrates defined in ISO 13640 (mortar, anodized aluminium or glass). Spacers and anti-adherent film are used to create and cure the sealant bead.
- Conditioning: Two conditioning routes:
- Method A - 28 days at (23 ± 2) °C and (50 ± 5) % RH.
- Method B - Method A followed by three cycles of heat (70 ± 2 °C) and water immersion (23 ± 2 °C), then 24 h at standard conditions.
- Elongation values: Typical elongations are 25 %, 60 % and 100 % (for a 12 mm initial width, corresponding to 15.0, 19.2 and 24.0 mm).
- Apparatus and measurement: Extension machine (5.5 ± 0.7 mm/min), ventilated oven, water container, vernier caliper (0.1 mm accuracy). Test environment: (23 ± 2) °C, (50 ± 5) % RH.
- Calculation: Elastic recovery R (%) is calculated as R = (We − Wr) / (We − Wi) × 100, where Wi = initial width, We = width under elongation, Wr = width after recovery. Results rounded to nearest 1%; report arithmetic mean of three specimens.
- Test report content: Laboratory ID and date, reference to ISO 7389, sealant type and batch, substrate and primer used, conditioning method, elongation %, individual and mean recoveries, and any deviations.
Applications and Who Uses It
- Sealant manufacturers: For product development, quality control and specification compliance.
- Independent test laboratories: Routine performance testing for clients and certification bodies.
- Architects and specifiers: To compare elastic performance of sealants when writing performance-based specifications for building joints.
- Contractors and facade engineers: To select sealants suitable for dynamic joints subject to movement and to validate product claims.
- Regulatory and certification bodies: To verify conformity with product standards and claims related to elasticity and durability.
Related Standards
- ISO 6927 - Sealants vocabulary and terms referenced by ISO 7389.
- ISO 13640 - Specifications for test substrates used to prepare specimens.
Keywords: ISO 7389, elastic recovery, sealants, jointing products, sealant testing, building construction, conditioning, extension test, test specimens.
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