Overview
ISO 9073-7:2024 - Nonwovens - Test methods - Part 7: Determination of bending length defines a laboratory method to measure the bending length of nonwoven materials and provides a formula to calculate flexural rigidity from that measurement. The procedure is specific to nonwovens and is not applicable to combination-type materials (composites or laminates) that exhibit natural twist.
Keywords: ISO 9073-7:2024, nonwovens test method, bending length, flexural rigidity, cantilever test.
Key topics and technical requirements
- Scope and definitions: Bending length is the cantilever length that bends under its own weight to an angle of 7.1°; flexural rigidity is derived from bending length and expressed in mN·cm.
- Specimen preparation: Cut specimens 25 mm × 250 mm (±1 mm) in both machine direction (MD) and cross-machine direction (CD), avoid edges/creases, condition in standard atmosphere (see ISO 139).
- Apparatus:
- Platform: (40 ± 2) mm wide, (200 ± 2) mm long, supported ≥150 mm above table; platform supports marked with lines at 41.5°.
- Steel rule: ~25 mm wide, 350 mm long, mass (250 ± 10) g, rubber underside.
- Optional motorized drive for consistent rule advance; timing accurate to ±1 s.
- Procedure summary:
- Measure mass per unit area (ISO 9073-1).
- Place specimen on platform, advance steel rule so specimen overhangs and bends under its own weight until leading edge reaches the 41.5° plane.
- After (8 ± 2) s read overhanging length; bending length = half the overhang.
- Repeat measurements (four readings per specimen) and test six specimens per direction.
- Calculations and reporting:
- Flexural rigidity G (mN·cm) computed using G = m × C × 9.81 (m = mass/area in g·m⁻², C = mean bending length in cm).
- Report mean values, coefficients of variation, number of specimens, test conditions and any deviations.
Applications and practical value
- Quality control: Routine production testing to monitor stiffness/handle of nonwoven rolls.
- Material specification & selection: Compare flexural rigidity across nonwoven grades for filters, hygiene products, geotextiles, packaging, and medical disposables.
- R&D and product development: Optimize fabric structure, basis weight and bonding to achieve desired drape and stiffness.
- Third‑party and contract testing: Provide standardized results for supplier contracts and compliance testing.
Who should use this standard
- Textile and nonwoven manufacturers, R&D engineers, QC laboratories, test houses, product designers, and procurement specialists who need repeatable, comparable measures of nonwoven stiffness and handle.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing
- ISO 186 - Sampling to determine average quality
- ISO 9073-1 - Nonwovens - Determination of mass per unit area
For implementers, follow the full ISO 9073-7:2024 text for detailed apparatus drawings, tolerances and reporting templates.