Overview
ISO 23658:2020 specifies a bead peel test method for evaluating the adhesion properties of construction sealants. It applies to one‑component and multi‑component sealants with a minimum elongation at break of 25% (per ISO 8339, Method A or B). The standard is primarily intended for elastic sealants but can also be used for plastic sealants (requiring experienced technicians). ISO 23658:2020 covers sample preparation, conditioning, optional ageing simulation, manual peel procedure and evaluation of failure patterns.
Key topics and requirements
- Scope: Adhesion assessment of sealant beads on various substrates including the influence of cleaners, activators and primers. Not a replacement for cohesion tests in ISO 11600.
- Sealant selection: Applies to products meeting the minimum elongation requirement (ISO 8339).
- Bead application methods:
- Without mold - for non‑sagging sealants; apply semicircular beads (typical height 5–8 mm; minimum bead length ~80 mm).
- With mold - for self‑leveling products using non‑adhesive spacers or foam tape.
- Conditioning and ageing: Curing as agreed between parties; artificial ageing cycles may be applied to simulate field exposure (examples given in Annex A).
- Peel test procedure: Manual peeling at a peeling angle of 130°–160°; iterative cutting and peeling to expose progressive adhesion behaviour; maintain stress intervals (~3–5 s) to reveal adhesion loss.
- Evaluation and reporting:
- Failure patterns recorded and graded in accordance with ISO 10365 (reported to nearest 10%).
- Test report must include sealant identification, substrates/coatings, surface pre‑treatment, bead application method, curing and ageing conditions, results, deviations and technician/date.
Applications
- Product development: Compare formulation adhesion with/without primers, cleaners or activators.
- Quality assurance & process monitoring: Routine adhesion checks during production and batch verification.
- Material compatibility assessment: Verify sealant performance on intended substrates (metal, glass, painted/coated surfaces).
- Durability testing: Assess adhesion retention after thermal, water immersion or other accelerated ageing steps.
Who uses this standard
- Sealant manufacturers and R&D teams
- Independent testing laboratories and QA departments
- Building envelope specifiers, façade engineers and contractors
- Regulatory and certification bodies evaluating jointing products
Related standards
- ISO 8339 - tensile properties (extension to break)
- ISO 10365 - designation of main failure patterns (evaluation)
- ISO 11600 - classification and requirements for sealants (not replaced by this method)
- ISO 554, ISO 9142 - referenced for conditioning and ageing guidance
Keywords: ISO 23658:2020, bead peel test, adhesion testing, construction sealants, elastic sealants, primers, ageing, quality assurance.