Overview
EN ISO 22088-6:2009 (ISO 22088-6:2006) specifies the slow strain rate method for assessing the susceptibility of plastics to environmental stress cracking (ESC). The procedure exposes tensile specimens to a defined chemical environment while a low, constant strain rate is applied. The test is primarily a ranking method to compare ESC susceptibility between materials or between environments and is not intended to supply design data.
Key topics and technical requirements
- Test principle: slowly increase strain on a tensile specimen while immersed in a test medium and monitor stress–strain behaviour to detect craze initiation and departure from the inert (air) response.
- Departure criterion: departure is defined objectively - when the derivative (tangent modulus) of the stress–strain curve in the test medium falls to 75% of that in air.
- Specimens: typically use Type 1BA tensile specimens per ISO 527-2; specimens may be moulded or machined.
- Apparatus:
- Tensile testing machine capable of a constant displacement rate with repeatability (crosshead speed) to ±2%.
- Load cell accuracy to about ±1%; displacement transducer accuracy to about ±0.4%.
- Grips with ripple contact to prevent slippage.
- Inert test chamber to contain specimen and test fluid without influencing results.
- Data-logging of load and displacement at intervals not exceeding 10 minutes.
- Conditioning and test conditions:
- Typical specimen conditioning at (23 ± 2) °C and (50 ± 10) % RH for at least 24 h.
- Default test temperature often (23 ± 2) °C unless otherwise agreed.
- Test medium should reflect service conditions or be prepared from reagent-grade chemicals.
- Results: focus on departure strain/stress as a repeatable ranking parameter; time-to-failure is variable and not generally used for ranking.
Applications
- Comparative evaluation of ESC susceptibility for material selection.
- Screening new polymer formulations or additives for chemical compatibility.
- Rapid compatibility checks of plastics with service fluids.
- Failure investigation and R&D where ESC ranking accelerates decision-making.
Who should use this standard
- Plastics engineers and material scientists evaluating chemical resistance.
- Test laboratories performing ESC susceptibility screening.
- Manufacturers of polymer products (containers, pipes, fittings, consumer goods) needing compatibility data.
- R&D teams and quality control groups conducting comparative ranking tests.
Related standards
- ISO 22088-1 - General guidance on ESC testing.
- ISO 527-2 - Tensile specimen dimensions and test conditions.
- Other parts of ISO 22088 (Parts 2–5) cover alternative ESC methods (constant-load, bent-strip, impression, constant-deformation).
Keywords: environmental stress cracking, ESC, EN ISO 22088-6, slow strain rate method, plastics testing, tensile specimen, ESC susceptibility, ranking test, ISO 527-2.