SIST EN ISO 16177:2013 PDF

Overview

EN ISO 16177:2012 - Footwear: Resistance to crack initiation and growth - Belt flex method specifies a laboratory test method to evaluate how components or materials (mainly outsoles) resist crack initiation and crack growth caused by repeated flexing. Published by CEN/ISO, the method replicates the short rapid flexing and longer unflexed periods experienced by footwear outsoles in use by mounting specimens on a driven cotton canvas belt and cycling them over crowned rollers.

Keywords: EN ISO 16177:2012, belt flex method, footwear testing, crack initiation, crack growth, outsole durability.

Key Topics and Technical Requirements

• Scope: Test method for outsole and other flexible footwear components to assess resistance to crack initiation and propagation under repeated flexing.
• Apparatus: Flexing machine with two crowned rollers (free-wheeling roller sized by sole thickness/expected service demand; driven roller 225 ± 5 mm diameter), and a continuous cotton canvas belt (~1930 mm length, 140 ± 5 mm width) with specified mass and tensile properties.
• Operating conditions: Belt speed and drive arranged to give approximately 90 ± 8 flexing cycles per minute (driven roller ~247 ± 20 r/min).
• Adhesives & surface prep: Use of a pre‑reacted PU adhesive and single‑component PU adhesive for bonding specimens to the belt. Material‑specific primers and surface treatments are required:
  • Halogenation primer for vulcanized/thermoplastic rubber
  • EVA primer for EVA materials
  • MEK wipe for PVC and solid thermoplastic PU
• Specimen preparation: Guidelines on cutting, thinning soles > 15 mm to 15 mm, surface scouring, and ageing (moulded specimens: wait ≥ 48 h before test).
• Bonding procedure: Heat-activate adhesive areas to 80–85 °C (verified with heat‑sensitive crayon), bond specimens, and condition the assembled belt ≥16 h at 23 ± 2 °C and 50 ± 2 % RH before cycling.
• Inspection & scoring: After flexing cycles, inspect and record cracks by position, length (nearest 1 mm) and depth classes:
  • Superficial: up to 0.5 mm
  • Shallow: 0.5–1.5 mm
  • Moderate: 1.5 mm to half specimen thickness
  • Deep: greater than half specimen thickness

Applications and Users

• Footwear manufacturers for quality control and production acceptance testing of outsoles.
• Material suppliers (rubber, PU, EVA) for validating formulation durability under flex fatigue.
• Test laboratories and certification bodies performing standardized durability tests for product claims.
• R&D and product development teams using results to compare designs, select materials, or troubleshoot cracking/failure modes.
• Compliance officers ensuring products meet market or contract durability requirements.

Related Standards

• ISO 20344 (referenced for specimen marking/figures)
• Prepared under collaboration between CEN/TC 309 and ISO/TC 216 (Footwear)

EN ISO 16177:2012 remains a practical, reproducible method for assessing outsole flex fatigue resistance and supporting product development, material selection, and conformity testing in the footwear industry.