Overview
ISO/TR 7620:2005 - Rubber materials - Chemical resistance is a Technical Report that defines a practical classification system and guidance for reporting, testing and evaluating the chemical resistance of rubber materials. Based on manufacturers’ and users’ experience, it covers behaviour of rubber in contact with aggressive gases and fluids (acids, alkalis, aqueous solutions, oils, solvents) and collates data for about 400 chemicals and roughly 25 rubber types. The report is informative-intended to assist material selection and assessment rather than to mandate a single test procedure.
Key topics
- Classification system (classes 1–4): Resistance graded by effects on volume (swelling) and hardness change, with complementary descriptions for other property changes (see Table 1 in the report).
- Class 1: volume change <10%, hardness change ≤10 IRHD - no significant effect
- Class 2: volume 10–30%, hardness ≤20 IRHD - minor effect
- Class 3: volume 30–60%, hardness ≤30 IRHD - moderate effect
- Class 4: volume >60% or hardness >30 IRHD - severe effect
- Physical vs chemical changes: Differentiates swelling/absorption, extraction of additives, hydrolysis, oxidation, and specific surface attacks (e.g., chlorine, ozone). Gas permeability is noted as outside the report’s scope.
- Rubber polymers covered: Lists common elastomers (NR, SBR, NBR, EPDM, IIR/CIIR/BIIR, CR, FKM, HNBR, silicone MQ/FMQ, various urethanes, etc.) and notes that thermoplastic rubbers are excluded due to insufficient data.
- Service-condition factors: Emphasizes temperature, concentration, contact time, pressure, product dimensions and dynamic vs static service impact on acceptable property changes.
- Testing guidance and references: Recommends confirming table selections by testing actual compounds under representative service conditions; refers to ISO test chemicals and standards (e.g., ISO 1817 reference oils) and includes annexes on compounding effects and source references.
Applications and users
Who benefits:
- Material engineers and polymer formulators selecting elastomers for seals, gaskets, hoses, linings, rollers and other rubber components
- Design and product engineers specifying compatibility for fluids, fuels, oils and chemicals
- Quality, procurement and testing laboratories validating compound performance
- Manufacturers of rubber goods and end-users in chemical processing, automotive, oil & gas, food/water contact and industrial equipment
Practical use:
- Pre‑selection of candidate rubbers by compatibility class
- Defining test conditions and acceptance criteria for qualification testing
- Assessing risks from mixed or commercial-grade chemicals and compounding variations
Related standards
- ISO 1817 (reference oils for swelling tests) is cited in the report; ISO/TR 7620 cross-references other ISO test methods and chemical listings to inform evaluation and tabulation of chemical resistance.
Keywords: ISO/TR 7620:2005, chemical resistance of rubber, rubber chemical compatibility, rubber testing, swelling, hardness change, rubber selection.