Overview
ISO 17694:2016 - Footwear - Test methods for uppers and lining - Flex resistance specifies a laboratory test method to determine the flex resistance of footwear uppers and linings irrespective of material. The method assesses a material’s tendency to crack, crease, flake or develop salt spue under repeated bending (flexing) to help judge suitability for end use. The procedure simulates the inward folding of a shoe vamp and can be performed in dry, wet or sub-zero conditions.
Key technical topics and requirements
- Test principle: Rectangular specimens are folded and clamped in a flexing machine (flexometer) so that inward and vertical folds are repeatedly flexed through a defined angle. Damage is visually assessed at set cycle intervals.
- Apparatus and parameters:
- Flexing angle: 22°30' ± 0°30';
- Oscillation speed: 100 ± 5 cycles/min;
- Distance between clamps (horizontal position): 25 ± 1 mm;
- Specimen press knife size typically 70 × 45 mm; specimen length must be 70 ± 1 mm.
- Conditioning and environments:
- Tests may be conducted dry, wet (using deionised water and vacuum impregnation) or cold (e.g., around –5 °C; lower temperatures may be used).
- Conditioning follows referenced atmospheres (see Related Standards).
- Sampling and orientation:
- Specimens are cut along and across the material’s backbone/warp directions; for uppers specimens should be taken from the forepart at the point of greatest flexing.
- Test direction: uppers tested face up, linings face down.
- Inspection stages:
- Recommended inspection cycle points include 1 000, 2 000, 5 000, 10 000, 25 000, 50 000 and 100 000 cycles (applicability varies by dry/wet/cold).
- Assessment criteria:
- Record creasing, visible or fine cracks (with magnifier), loss of adhesion, greying, powdering/flaking, broken yarns (textiles), and salt spue grading (light/marked/heavy).
Practical applications and users
- Who uses it: footwear manufacturers, material suppliers, independent testing laboratories, R&D and QA teams, product developers and certification bodies.
- Typical uses:
- Compare flex durability of leathers, coated fabrics, textiles and lining materials.
- Support material selection and design decisions for durability and end-use performance.
- Quality control and batch verification to detect manufacturing or coating failures.
- Failure analysis (cracking, adhesion loss, salt spue) to drive corrective actions.
Related standards
- ISO 5402-1:2011 - Determination of flex resistance (flexometer method)
- ISO 17709 - Sampling location and conditioning of footwear test pieces
- ISO 18454 - Standard atmospheres for conditioning and testing
- ISO 3696 - Water for analytical laboratory use
Keywords: ISO 17694:2016, flex resistance, footwear testing, uppers and lining, flexometer, durability testing, salt spue, material selection, quality control.
