ISO 26842-2:2020

Overview

ISO 26842-2:2020 sets out test methods and selection guidelines for adhesives used in indoor wood products that must resist delamination in severe environments (extreme temperature and humidity changes). The standard defines exposure cycles, specimen preparation and assessment criteria so manufacturers and suppliers can verify adhesive/wood combinations for high-durability indoor or semi-outdoor applications.

Key topics and technical requirements

• Scope & purpose: Evaluate adhesive/wood combinations for resistance to delamination under severe environmental cycles; not intended for qualification of structural components.
• Specimen preparation: Parallel two‑ply laminates, nominally 300 × 300 × 7.5 mm, prepared and measured in accordance with ISO 6238, ISO 9424 and ISO 16999. Minimum 10 specimens per grade/condition.
• Conditioning: Pre-test conditioning at (23 ± 2) °C and (50 ± 5) % RH for at least 7 days (or as agreed).
• Delamination-resistance grades:
  • Grade 3 - high-durability indoor use (e.g., chair legs, musical instruments)
  • Grade 4 - semi-outdoor use (e.g., window frames, flooring near windows)
• Four test types (representing service/transport meteorological conditions):
  • Test A (cyclic hot/cold) - A1: −30 °C (16 h) / 80 °C (8 h); A2: −20 °C (16 h) / 50 °C (8 h)
  • Test B (cyclic humid/dry) - B1: 50 °C, 90 % RH (2 days) / 50 °C, 20 % RH (5 days)
  • Test C (hot & humid) - C1: 50 °C, 90 % RH
  • Test D (hot & dry) - D1: 50 °C, 20 % RH
• Test schedules: e.g., Grade 3: A2 (10 cycles), B1 (1 cycle), C1 (7 days), D1 (7 days). Grade 4 uses more severe durations (e.g., A1 10 cycles, C1/D1 14 days).
• Assessment & acceptance: Measure delamination within 1 hour after exposure using ~10× magnification; record delamination lengths to nearest 1 mm. Acceptance criterion: total delamination ≤ 10 % of bond-line length across specimens. Exclude wood checks/knots from delamination measurement.
• Apparatus notes: Climate chambers (conditioning, dry-heat, cold, humidity) with air circulation ~2.25 ± 0.25 m/s.

Applications & users

This standard is practical for:

• Adhesive manufacturers validating product performance for indoor wood uses
• Wood product manufacturers selecting adhesives for furniture, flooring, window frames and other items exposed to varying microclimates
• Test laboratories performing delamination-resistance testing and reporting compliance
• R&D teams optimizing formulations for delamination resistance in severe environments

Note: When testing actual finished products, results can vary because assembly and manufacturing controls differ-ISO 26842-2:2020 cautions about comparability.

Related standards

• ISO 6238 - wood-to-wood adhesive bond shear strength by compressive loading
• ISO 9424 - dimensions of wood-based panel test pieces
• ISO 16999 - sampling and cutting of test pieces

Keywords: ISO 26842-2:2020, delamination resistance, adhesives for wood, test methods, climate chamber, cyclic hot/cold, humidity cycles, indoor wood products.