Overview
ISO 29765:2008 specifies a standardized test method to determine the tensile strength perpendicular to faces of thermal insulating products used in buildings. The standard defines the equipment, specimen preparation, conditioning, test procedure and result reporting so manufacturers, test laboratories and specifiers can obtain comparable, reproducible tensile-strength data for insulation materials.
Key topics and technical requirements
- Scope: Applies to thermal insulating products and covers equipment and procedures for measuring tensile strength perpendicular to faces (σmt).
- Principle: A square-prism specimen is bonded between two rigid plates/blocks, loaded in a tensile testing machine and pulled at constant speed until failure. The maximum force is recorded and tensile strength calculated as F/A.
- Apparatus:
- Tensile testing machine with constant crosshead speed of (10 ± 1) mm/min and force measurement accuracy ±1%.
- Self-aligning rigid plates or blocks to avoid uneven stress distribution.
- Adhesive compatible with the product (must not reinforce or damage surface layers; avoid damaging hot adhesives or incompatible solvents).
- Specimens:
- Thickness equals original product thickness including skins/facings/coatings.
- Recommended square cross sections: 50×50, 100×100, 150×150, 200×200 or 300×300 mm (use sizes specified in the relevant product standard).
- At least 5 specimens if the product standard does not specify a number.
- Cut so base is normal to in-use tensile direction; retain facings/skins; avoid edges (preferably ≥15 mm from edges).
- Conditioning and test conditions:
- Standard conditioning: at least 6 h at (23 ± 5) °C; in dispute use (23 ± 2) °C and 50 ± 5% RH.
- For tropical conditions: 27 °C and 65% RH (must be recorded in the report).
- Calculation and results:
- Tensile strength σmt = F (kN) / A (m²). Report mean value to two significant figures.
- Discard specimens failing in the adhesive layer.
- Accuracy / precision:
- 95% repeatability ≈ 5%; 95% reproducibility ≈ 15% (per ISO 5725 principles).
Applications and who uses it
- Quality control and production testing for insulation manufacturers.
- Independent testing laboratories and certification bodies for compliance and product labeling.
- Product development / R&D to compare materials and facings.
- Architects, specifiers and building engineers who require performance data for material selection.
- Procurement and building code compliance verification.
Related standards
ISO 29765 is part of a suite of ISO test methods for thermal insulating products (examples):
Keywords: ISO 29765:2008, tensile strength perpendicular to faces, thermal insulating products, tensile testing, specimen conditioning, insulation test method, building insulation testing.
Open preview (PDF)Thermal insulating products for building applications — Determination of tensile strength perpendicular to faces