Overview
ISO 4658:2020 - "Acrylonitrile-butadiene rubber (NBR) - Evaluation procedure" defines standardized methods for evaluating raw NBR (acrylonitrile‑butadiene rubber). The standard covers sampling and sample preparation, physical and chemical tests on raw rubbers, a standard test formulation, and defined equipment and mixing procedures (preferred single‑stage LIM mixing) for assessing vulcanization characteristics and tensile properties.
Key Topics
- Scope and sampling
- Sample mass ≈ 1.5 kg; sampling and preparation per ISO 1795.
- Physical/chemical tests on raw NBR
- Standard test formulation (parts by mass)
- NBR 100.00, Zinc oxide 3.00, Sulfur 1.50, Stearic acid 1.00, Carbon black 40.00, TBBS 0.70 (total 146.20).
- TBBS = N‑tert‑Butyl‑2‑benzothiazole sulfenamide; insoluble‑matter checks (replace/recrystallize if > 0.75%).
- Mixing procedures
- Method A1 (preferred): single‑stage mixing with a laboratory internal mixer (LIM) - final batch temp ≤ 120 °C; LIM cooled to 60 °C between batches.
- Method A2: two‑stage mixing - LIM initial mix, final mill mixing.
- Method B: mill mixing.
- Equipment and general mixing procedures per ISO 2393. Conditioning 2–24 h after mixing (ISO 23529).
- Vulcanization and mechanical evaluation
- Precision & reporting
- Precision data provided in Annex A; test report requirements specified.
Applications
ISO 4658:2020 is used to:
- Standardize QC testing of NBR batches for manufacturing and incoming inspection.
- Support R&D and compound optimization (comparing cure behavior, scorch, crosslinking).
- Specify supplier acceptance criteria and contractual material evaluation.
- Provide reproducible inputs for product development in automotive seals, hoses, gaskets, and oil‑resistant components where NBR is used.
Who uses it: rubber technologists, laboratory analysts, compounders, OEM material engineers, testing labs, and procurement teams.
Related Standards
Keywords: ISO 4658, NBR evaluation, acrylonitrile‑butadiene rubber, Mooney viscosity, vulcanization testing, laboratory internal mixer, LIM mixing, curemeter, rubber testing standard.