Overview
ISO 5402-2:2015 is an international standard specifying a precise method for determining the flex resistance of leather materials and their finishes using the vamp flex method. Applicable to all leather types with a thickness under 3.0 mm, this standard enables accurate assessment of both wet and dry flex durability. Developed by the International Organization for Standardization (ISO) in collaboration with the International Union of Leather Technologists and Chemists Societies (IULTCS) and the European Committee for Standardization (CEN), ISO 5402-2 ensures consistent, repeatable leather testing worldwide.
Key Topics
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Scope and Purpose
Focuses on measuring leather’s resistance to flexing under wet and dry conditions, specifically valuable for thinner leather materials (below 3.0 mm thickness).
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Test Principle
The test piece is folded over two inverted “V” shaped clamps and subjected to harmonic reciprocating motion, causing repeated creasing and flexing. The leather is periodically inspected for damage such as cracking, creasing, delamination, or spue (wet flex only).
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Apparatus Requirements
- Two inverted “V” shaped clamps with specific dimensions and internal angles
- A machine capable of reciprocating motion at 300 ± 30 cycles per minute
- A counter to track flex cycles
- Additional equipment like a magnifier (4-6x magnification), press knife for sample preparation, and distilled/deionized water for wet tests
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Sampling and Preparation
Sampling follows ISO 2418 guidelines, with test pieces cut parallel and perpendicular to the backbone of the leather. Conditioning and wetting procedures are aligned with ISO 2419 and ISO 3696 standards respectively.
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Testing Procedure
Leather samples are flexed for prescribed cycles (up to 1,000,000 for dry tests and 100,000 for wet tests) with intermediate examinations. Damage is recorded after each inspection point. Wet samples are re-wetted every 25,000 flex cycles to simulate real usage conditions.
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Reporting
The test report must detail the leather sample identification, testing conditions (wet or dry), number of flex cycles, observed damage, conditioning atmosphere, and any deviations from the method.
Applications
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Quality Control in Leather Manufacturing
Enables manufacturers to verify the durability and flexibility of leather products, ensuring material performance meets specified criteria before market release.
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Product Development and R&D
Assists researchers and developers in assessing new leather treatments, finishes, and tanning processes to enhance flex resistance properties.
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Compliance and Certification
Provides a standardized testing methodology for industry-wide compliance; useful for certification bodies and regulatory purposes ensuring leather products meet international durability standards.
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Footwear and Upholstery Industries
Particularly relevant for components like vamps in footwear that undergo continuous flexing, enhancing product reliability and customer satisfaction.
Related Standards
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ISO 5402-1: Leather - Determination of flex resistance - Part 1: Flexometer method
An alternative testing method for leather flex resistance, suitable for different conditions or thickness ranges.
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ISO 2418: Leather - Sampling location
Guidelines for selecting representative sample locations on hides or skins for accurate testing.
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ISO 2419: Leather - Sample preparation and conditioning
Specifies procedures for preparing and conditioning leather samples, crucial for consistent testing results.
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ISO 3696: Water for analytical laboratory use - Specification and test methods
Defines water quality required for wet flex tests to ensure consistent and valid results.
By adhering to ISO 5402-2:2015, leather manufacturers, researchers, and quality assurance professionals can accurately assess the flex resistance of leather goods, ensuring durability and performance in end-use applications. This internationally recognized vamp flex method contributes to the development of longer-lasting leather products and helps maintain high standards in leather technology.
