Overview
EN ISO 22088-4:2006 (ISO 22088-4:2006) specifies the ball or pin impression method to determine the resistance of plastics to environmental stress cracking (ESC) using a constant‑strain test. The method applies to finished products and to specimens prepared by moulding or machining and is intended to assess ESC behaviour of a plastic material or product when exposed to chemical environments. The standard is quick and sensitive, especially for amorphous plastics, and supersedes EN ISO 4600:1997.
Key topics and technical requirements
- Test principle: Drill and ream a hole in the specimen, insert an oversize ball or pin to impose a constant strain, then expose the assembly to a chemical medium and monitor for ESC.
- Deformation series: Tests are carried out in successive deformation steps (a deformation series typically consists of seven increasing steps) beginning with a zero‑impression step.
- Specimen types:
- Type A - finished products: evaluation chiefly by visual inspection for cracks (×5 magnification).
- Type B - moulded/machined specimens: evaluated by mechanical testing (tensile or flexural) against defined failure criteria.
- Failure criteria (Type B): mechanical thresholds such as a 5% reduction in maximum tensile or flexural force or a 20% reduction in tensile elongation at rupture compared with deformation step zero (alternative B4 criterion may be used if rupture does not occur immediately).
- Applicability:
- Well suited to amorphous plastics; pins are preferred for thin or semi‑crystalline materials (which show creep/stress relaxation).
- Intended for comparative assessment of materials/environments or product qualification.
- Test conditions & conditioning: Specimens must be conditioned and tested under controlled atmospheres and temperatures (referenced normative standards such as ISO 291).
- Result expression: Includes determination of a failure limit and calculation of a relative stress‑cracking factor (ratio of failure limit in test environment to that in a reference environment).
Applications and users
Who uses EN ISO 22088-4:2006:
- Materials and polymer engineers assessing chemical resistance
- Quality control and R&D laboratories for product qualification
- Manufacturers of plastic components and finished products (e.g., housings, fittings)
- Certification bodies and compliance testing labs
Typical applications:
- Screening plastics and formulations for susceptibility to environmental stress cracking
- Comparing chemical environments or stress levels for a given material
- Verifying finished parts and prototypes for field exposure risks
Related standards
- ISO 22088 series (general guidance and complementary methods):
- Normative references commonly used with this method: ISO 291 (conditioning), ISO 527 (tensile testing), ISO 178 (flexural testing), ISO 3290 (balls).
Keywords: EN ISO 22088-4:2006, ISO 22088-4, environmental stress cracking, ESC testing, ball or pin impression method, plastics testing, constant‑strain test.
