Overview
EN ISO 22088-3:2006 - "Plastics - Determination of resistance to environmental stress cracking (ESC) - Part 3: Bent strip method" specifies a laboratory method to rank the ESC resistance of thermoplastics when subjected to a fixed flexural (bent) strain in the presence of chemical agents. Commonly referenced as the bent strip method (ISO 22088-3:2006), the test indicates ESC by monitoring a chosen indicative property of flat or sheet specimens after a defined exposure time. The method is primarily a comparative (ranking) test and is not intended for design or quantitative performance prediction.
Key Topics and Requirements
- Test principle: Specimens are clamped over circular forms to apply a nominal tensile surface strain, exposed to a test medium (liquid, gas or solids with migrating substances), then inspected or mechanically tested for ESC effects.
- Specimen types: Flat test pieces and sheets; particularly useful to assess sensitivity of localized surface regions.
- Strain control: Series of decreasing form radii produce increasing surface strains. Maximum applied strain must remain below the material’s strain at yield.
- Typical dimensions: For specimens 2–4 mm thick, recommended form radii range from about 30 mm to 500 mm (document gives equation linking radius, thickness and chord).
- Indicative properties & failure criteria: Visual surface defects (crazes/cracks) or mechanical properties (tensile, flexural, impact) - e.g., reduction thresholds such as 80 % of original stress or 50 % of impact strength are suggested criteria (see standard for full table).
- Data expression: Failure strain and ESC index (ratio of failure strain in test medium to that in reference medium, usually air) are used for comparative evaluation.
- Apparatus & conditioning: Chemical-resistant forms, light clamps, vessels for the medium, thickness micrometer, and instruments to measure the chosen indicative property. Conditioning and test temperature/medium are specified in the standard.
Applications and Users
- Useful for materials development, quality control and comparative screening of rigid thermoplastics.
- Typical users: polymer manufacturers, product designers assessing material/chemical compatibility, testing laboratories, packaging, automotive and electronics part suppliers, and adhesive formulators evaluating migrating plasticizers.
- Particularly valuable when assessing ESC caused by gases, liquids or migrating substances (e.g., adhesives or plasticizer-containing materials) contacting polymer surfaces.
Related Standards
This summary highlights practical use and scope of EN ISO 22088-3:2006, helping labs and engineers choose appropriate ESC screening methods for thermoplastic materials.
