ISO 2302:2020

Overview

ISO 2302:2020 - "Isobutene‑isoprene rubber (IIR) - Evaluation procedure" - is the international standard that defines a complete, repeatable procedure for evaluating the vulcanization characteristics and basic physical/chemical properties of all types of isobutene‑isoprene rubber (IIR). Published in 2020 (7th edition), it specifies sampling, raw‑rubber tests, a standardized test formulation, mixing and processing methods, curemeter testing and tensile testing procedures for laboratory evaluation.

Key topics and technical requirements

• Scope and sampling
  • Sampling and laboratory sample preparation are specified in accordance with ISO 1795.
• Raw‑rubber tests
  • Mooney viscosity (ML(1+8) at 125 °C) per ISO 289‑1.
  • Volatile matter by ISO 248‑1 (hot‑mill/oven) or ISO 248‑2 (TGA).
  • Ash determination per ISO 247‑1 (combustion/TGA methods).
• Standard test formulation
  • Provides a fixed compound recipe (parts by mass): IIR 100, stearic acid 1.00, industry reference carbon black 50.00, zinc oxide 3.00, sulfur 1.75, tetramethylthiuram disulfide (TMTD) 1.00 - total 156.75.
  • Allows replacement of TMTD with an alternative curative (e.g., TBzTD) to avoid toxic releases.
• Mixing and processing
  • Mixing and vulcanization equipment/procedures follow ISO 2393.
  • Three mixing methods are specified: Method A (mill mixing), Method B (single‑stage laboratory internal mixer - preferred), and Method C (two‑stage mixing).
  • Limits on discharge temperature, batch mass tolerances and conditioning times (2–24 h) are defined.
• Vulcanization and mechanical testing
  • Vulcanization behavior measured with curemeters (oscillating‑disc or rotorless) per ISO 6502 series.
  • Tensile stress‑strain testing of vulcanizates per ISO 37.
• Quality assurance
  • Precision data, required test reporting elements and laboratory practice warnings are included.

Applications and users

ISO 2302:2020 is used for:

• Quality control and acceptance testing of IIR raw materials and compounds.
• R&D and formulation development to compare vulcanization behavior.
• Supplier verification and benchmarking of IIR grades.
• Rubber test laboratories, compounders, tire and sealing manufacturers, materials engineers and regulatory labs that evaluate IIR performance.

Practical benefits include consistent cross‑laboratory comparability, standardized compound recipes for benchmarking, and clear mixing/vulcanization procedures to reproduce cure characteristics.

Related standards

Key referenced standards (normative):

• ISO 1795 (sampling and preparative procedures)
• ISO 289‑1 (Mooney viscosity)
• ISO 248‑1 / ISO 248‑2 (volatile matter)
• ISO 247‑1 / ISO 247‑2 (ash)
• ISO 2393 (test mixes: preparation, mixing, vulcanization)
• ISO 6502‑1 / ISO 6502‑2 (curemeter methods)
• ISO 37 (tensile properties)
• ISO 23529 (conditioning of test pieces)

Note: Users should follow normal laboratory safety practices; the standard contains a safety warning and permits alternative curatives to reduce toxic releases.