Overview
ISO 20875:2018 specifies standardized test methods for assessing the mechanical integrity of footwear outsoles by measuring split tear strength and delamination resistance. The standard defines specimen preparation, apparatus, test speeds and procedures, result expression and reporting requirements so manufacturers and testing laboratories can obtain repeatable, comparable data on outsole tear propagation and adhesive layer performance.
Key Topics and Requirements
- Scope: Method for determining split tear strength and delamination resistance of outsoles (ISO 20875:2018).
- Specimen dimensions & sampling: Test strips at least 75 mm long and 25 mm ± 0.2 mm wide; sampling and preparation in accordance with ISO 17709.
- Conditioning: Test pieces conditioned in standard atmospheres per ISO 18454 for a minimum of 24 hours before testing.
- Apparatus:
- Tensile-testing machine compliant with ISO 7500-1 (grade B accuracy) with low inertia and autographic force recording.
- Splitting jig and knife for initial cut/split preparation.
- Test parameters: Constant traverse rate of 100 mm/min ± 10 mm/min for both delamination and split tear tests.
- Delamination test: For multilayer outsoles, separate layers about 10 mm using a heated knife, clamp folded tongues in grips, record force vs. deformation while propagating the delamination.
- Split tear test: Pre-split one end ~30 mm using the splitting jig, fold tongues into grips and record force while propagating the tear.
- Expression of results:
- Delamination resistance D (N/mm) = average force F divided by specimen width d; results are the average of three values.
- Split tear strength ST (N/mm) = median force F divided by width d; results are the median of three values.
- Test report must include: measured results, sample identification (style, colour, material), reference to ISO 20875:2018, date, any deviations, and test atmospheric conditions.
Applications and Users
- Footwear manufacturers use ISO 20875 to validate outsole materials, adhesives and construction methods for durability and quality control.
- Independent testing laboratories implement the method for compliance testing, supplier verification and product certification.
- R&D teams and material suppliers apply results to compare rubber, EVA, TPU and bonded multilayer outsoles or to optimize adhesive systems.
- Quality assurance and procurement professionals rely on standardized N/mm metrics to set product specifications and supplier acceptance criteria.
Related Standards
- ISO 7500-1 - Calibration and verification of tensile-testing machines (force-measuring system)
- ISO 17709 - Sampling location, preparation and conditioning duration for footwear
- ISO 18454 - Standard atmospheres for conditioning and testing of footwear
- ISO 20344 - Test methods for footwear (bibliography reference)
Keywords: ISO 20875:2018, footwear outsoles, split tear strength, delamination resistance, test method, tensile-testing machine, outsole testing, N/mm.
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