ISO 23475-2:2025

Overview - ISO 23475-2:2025 (Adhesion test for steel tyre cord)

ISO 23475-2:2025 defines a standardized adhesion test method for steel cords used in tyre reinforcement. The method measures the force required to pull steel cords linearly out of a vulcanized rubber block (a pull‑out test) and evaluates the rubber coverage on the cord surface. The standard is intended for laboratory and quality‑control testing of steel tyre cords to ensure reliable bonding between cord and rubber.

Key topics and technical requirements

• Principle: Steel cords are vulcanized into a rubber block and pulled out; the maximum pull‑out force is recorded. A circular hole in the block holder ensures homogeneous stress distribution.
• Sample preparation: Four different cord samples are recommended, each fused into three specimens (e.g., 1‑1, 1‑2, 1‑3). Reference material (RM) can be used for internal monitoring.
• Rubber compound handling: Storage rules are specified (laboratory: 18 °C ±5 °C, 40–55 % RH, 1‑month shelf life; refrigerator: 5 °C ±5 °C, 3‑month shelf life). Target rubber thickness for the block is 7.5 mm ±0.5 mm.
• Apparatus: Includes lab rubber mixing mill (rollers ≈160 mm diameter), thickness gauge (0.1 mm resolution), vulcanization press (plate min 400×400 mm, temperature tolerance ±1 °C, max 200 °C, min pressure 3.5 MPa), tensile test machine, vulcanization moulds (embedded widths 12.5 mm and 25 mm), and a block holder.
• Vulcanization and conditioning: Preheat moulds, assemble rubber block with cords, vulcanize, then condition the block at room temperature (typically >16 h and <72 h unless agreed otherwise).
• Measurement & reporting:
  • Typical pull speed: 100 mm/min (or as agreed with customer).
  • Record maximum pull‑out force to the nearest 1 N; report average of three specimens per sample.
  • Evaluate rubber coverage with a percentage scale (0–100 %) and report average coverage to the nearest 1 %.
• Annexes: Informative annexes detail mould, top‑plate and block‑holder design and tolerances.

Applications and users

ISO 23475-2 is used by:

• Tyre cord manufacturers and suppliers for product qualification and batch verification
• Automotive tyre manufacturers (OEMs) for incoming material inspection and supplier audits
• Independent testing laboratories and R&D teams for comparative adhesion testing and process development
• Quality assurance and certification bodies assessing cord–rubber bonding performance

Practical benefits include consistent, reproducible adhesion data for supplier acceptance, process control, and materials development.

Related standards

• ISO 23475 series (other parts covering steel tyre cord testing)
• ISO 17832 (normative reference for terms and definitions on non‑parallel steel wire and cords)

Keywords: ISO 23475-2:2025, steel tyre cord adhesion test, pull‑out test, tyre reinforcement, vulcanization mould, rubber compound, tensile test, cord–rubber bonding.