ISO 7389:2002

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.