Overview
EN ISO 17232:2025 - Leather - Physical and mechanical tests - Determination of heat resistance of patent leather (ISO 17232:2025) is a CEN-adopted ISO draft that specifies two standardized methods to assess the heat resistance of patent (varnished) leather. Both methods are applicable to patent leathers for all end uses and are intended for routine quality control, product development and compliance testing.
Key topics and technical requirements
- Two test methods
- Method A - Lastometer method
- Uses a modified lastometer with a plunger terminating in a steel ball (Ø 21.0 ± 0.1 mm).
- Test piece clamped to leave a central free circular area (Ø 25.0 ± 0.1 mm).
- Specimen is distended by 7.5 mm ± 0.05 mm, heated and inspected.
- Standard heating: 100 ± 5 °C for 180 ± 5 s; extended condition: 125 ± 5 °C for 300 ± 5 s.
- Method B - Zwik method
- Uses the “Zwik” apparatus with a half-cylinder mandrel (radius 15.0 ± 0.1 mm, length 25.5 ± 0.1 mm) and defined clamp geometry.
- Test piece is stretched over the mandrel to a linear extension of 21 ± 1 %.
- Six test pieces are prepared (three with long edge parallel to backbone, three perpendicular).
- Specimen preparation and conditioning
- Selection and cutting of specimens in accordance with ISO 2418.
- Conditioning per ISO 2419; tests are carried out shortly after conditioning.
- Apparatus & measurements
- Hot air blower capable of required temperatures; temperature measurement to 1 °C; timing to 1 s.
- Specific cutting and perforation tools (press knife, sewing needle specifications) described.
- Test reporting
- Reports must reference ISO 17232:2025 and the method used, record damage before and after heating, state test temperature/time, conditioning atmosphere, specimen identification and any deviations.
Applications and users
- Who uses it
- Leather manufacturers and finishers, footwear and fashion brands, upholstery and accessory producers, independent test laboratories, and conformity assessment bodies.
- Practical uses
- Quality control of patent leather finishes to ensure resistance to heat-induced cracking, crazing or coating failure.
- Supporting material selection for products exposed to elevated surface temperatures (e.g., footwear near heat sources, vehicle interiors, display samples).
- Comparative testing during formulation or process changes to varnish systems and backing materials.
Related standards
- ISO 2418 - Specimen position and preparation
- ISO 2419 - Specimen conditioning (physical and mechanical tests)
- ISO 15115 / EN 15987 - Leather vocabulary and terminology
Keywords: ISO 17232:2025, patent leather heat resistance, lastometer, Zwik apparatus, leather testing, heat resistance test, CEN leather standards.
