Overview
ISO 8340:2005 - Building construction - Sealants - Determination of tensile properties at maintained extension - defines a standardized laboratory method to assess how sealants used in building joints behave when held at a fixed elongation. The standard specifies specimen preparation, conditioning, test temperatures, controlled extension levels and the measurement of any loss of adhesion or cohesion after a maintained extension period. This test complements other tensile tests (see Related Standards) and is used to evaluate sealant performance under sustained deformation.
Key topics and requirements
- Scope and principle: Measures tensile properties at maintained extension for sealants used in building construction joints; records loss of adhesion/cohesion when a specimen is held at a defined elongation.
- Specimen preparation: Sealant is installed between two parallel substrate pieces (mortar, anodized aluminium or glass as preferred) using spacers and an anti-adherent backing; manufacturer instructions (primers, mixing) are followed.
- Conditioning methods:
- Method A: 28 days at (23 ± 2) °C and (50 ± 5)% RH.
- Method B: Method A followed by three cycles of heat and water exposure (oven at 70 ± 2 °C and distilled water at 23 ± 2 °C), then 24 h at (23 ± 2) °C/50 ± 5% RH.
- Test procedure:
- Conduct tests at (23 ± 2) °C and (−20 ± 2) °C.
- Extend specimens at (5.5 ± 0.7) mm/min to 25%, 60% or 100% of original width (examples: 15 mm, 19.2 mm, 24 mm) or another agreed elongation.
- Maintain the extension for 24 h using separators; measure depth of any adhesion/cohesion loss to 0.5 mm accuracy.
- Equipment: Tensile test machine, refrigerated enclosure (for −20 °C conditioning), ventilated oven, distilled water container and calibrated measuring device.
- Test report: Must include lab name/date, reference to ISO 8340, sealant identification (type, colour, batch), substrate, primer, conditioning method, elongation level, measured depth of loss of adhesion/cohesion for each specimen and any deviations.
Applications and users
ISO 8340:2005 is used by:
- Sealant manufacturers for product development and internal quality control
- Independent testing laboratories for performance verification and certification
- Specifiers, architects and façade engineers to compare sealant performance under sustained movement
- Procurement and compliance teams to ensure products meet contractual or regulatory requirements
Practical applications include verifying suitability of sealants for expansion joints, curtain-wall junctions, window perimeter sealing and other construction interfaces where sustained extension may occur.
Related standards
- ISO 6927 - Sealants vocabulary (definitions)
- ISO 8339 - Determination of tensile properties (extension to break)
- ISO 13640 - Test substrates specification
Keywords: ISO 8340:2005, sealants, tensile properties, maintained extension, building construction, adhesion, cohesion, conditioning, tensile test.
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