Information on the most widely used ASTM standards within the materials testing industry
ISO 22088-3:2006 Plastics — Determination of resistance to environmental stress cracking (ESC) Part 3: Bent strip method
ISO 22088-3:2006 is an international standard specifying the bent strip method for determining the environmental stress cracking (ESC) resistance of thermoplastics when subjected to fixed flexural strain in the presence of chemical agents. It is the current replacement for the withdrawn ISO 4599:1986 standard and forms part of the ISO 22088 series on environmental stress cracking resistance testing.

Key principle:
The core principle of ISO 22088-3 is to evaluate a material's ability to resist crack formation and propagation when exposed to a chemical environment while under controlled mechanical stress (flexural strain).
Bend the rectangular plastic sample into a U shape and fix it, so that a constant strain is generated on its surface, and then expose it to a specific chemical reagent environment. The ESC resistance is evaluated by observing the appearance of surface cracks or changes in physical properties of the sample after a specified time. This method is suitable for ranking tests of sheets and rigid plastics (with moderate stress relaxation levels).
*A flat test specimen is bent over a former of known radius to create a fixed flexural strain (εₓ) on its tensile surface.
*The strained specimen is exposed to a test environment (liquid, gas, paste, or solid) for a specified duration.
*Environmental exposure combined with mechanical stress accelerates crack formation (environmental stress cracking).
*After exposure, specimens are visually inspected and tested for a chosen indicative property (e.g., tensile strength, impact resistance).
*A series of formers with decreasing radii (increasing strain) is used to determine the failure strain corresponding to a specific failure criterion.
*The test is essentially a ranking test and not intended to provide data for direct design or long-term performance prediction without additional correlation data.
Test device / equipment required:
| Equipment Component | Specifications |
|---|---|
| Formers | Chemical-resistant material (stainless steel), radii of curvature 30-500 mm (for 2-4 mm thick specimens), arc length matching specimen length, may be perforated for better wetting. Apply controlled strain to test specimens. |
| Clamps | Chemical-resistant material, lightweight to avoid additional stress, designed to secure specimens without damaging them. Fasten specimens to formers while maintaining uniform strain |
| Vessels | Clean glass containers with tight-fitting lids (or other non-reactive materials); Hold test environment and mounted specimens. |
| Test Environment | Analytical grade (or agreed technical grade) chemical media (e.g., Igepal CO-630 for polyethylene); Provide the environmental stressor. |
| Micrometer | Calibrated to 0.01 mm precision. Measure specimen thickness for strain calculation. |
| Indicative Property Test Equipment | Tensile testing machine (ISO 527), flexural tester (ISO 178), Charpy impact tester (ISO 179). Measure mechanical properties after exposure. |
| Temperature Control | Thermostatically controlled chamber (23°C ± 2°C, 40°C ± 2°C, or 55°C ± 2°C). Maintain consistent test temperature. |
Test Specimen Information:
Flat rectangular strips, typically 80-120 mm × 10-20 mm × 2-4 mm (thickness is critical for strain calculation).
When machined from sheets/articles, thickness must equal original material thickness.
Cut edges must have a clean finish, free from burrs or defects that could initiate cracks.
Testing Methods and Steps
1, Sample Preparation
Material: Sheet or flat samples, dimensions according to standard requirements (usually strip-shaped).Requirements: Surface without defects, edges smooth and burr-free, to avoid local stress concentration.
2, Bending and Fixing
Bend the sample along its length to the predetermined curvature (U-shape) and use clamps to secure both ends. The bending strain level must be calculated and set according to material characteristics, ensuring that the tensile area of the sample surface reaches the target strain value.
3, Environmental Exposure
Immerse the fixed bent sample in selected chemical reagents (liquid/gas) or contact solids containing migrating substances (such as plasticizer materials). Control environmental temperature (usually 23±2°C) and exposure time (set according to material characteristics, such as 24h, 48h, etc.).
4, Result Evaluation
Qualitative Assessment: Visually inspect the number, length, and distribution of cracks on the surface of the exposed sample (quantify to an accuracy of ±0.01mm).
Quantitative Assessment: Measure changes in physical properties (such as tensile strength decay rate ≥15MPa or critical value of elongation at break ≥200%), comparing to data from unexposed samples. Record the time of the first appearance of cracks or the degree of performance decay over a specific time as an ESC resistance indicator.
![]() |
| ISO 22088-3 Test Indicative Property Failure Criteria |
Through these steps, the crack resistance of plastic materials under specific environmental conditions can be effectively measured, thereby assisting in the selection of suitable materials for different application scenarios.
Related Standards:
| Related Standard | Description | Relationship |
|---|---|---|
| ISO 22088-1:2006 | General guidance for environmental stress cracking resistance testing | Parent standard providing overall framework |
| ISO 22088-2:2006 | Constant tensile load method | Alternative ESC test method |
| ISO 22088-4:2006 | Ball or pin impression method | Alternative ESC test method |
| ISO 22088-5:2006 | Constant tensile deformation method | Alternative ESC test method |
| ISO 22088-6:2006 | Slow strain rate method | Alternative ESC test method |
| ISO 527 | Plastics - Determination of tensile properties | Used for measuring indicative property (tensile strength) |
| ISO 178 | Plastics - Determination of flexural properties | Used for measuring indicative property (flexural strength) |
| ISO 179 | Plastics - Determination of Charpy impact resistance | Used for measuring indicative property (impact strength) |
| ISO 291 | Plastics - Standard atmospheres for conditioning and testing | Specifies conditioning parameters |
| ISO 294 | Plastics - Injection molding test specimens | For preparing molded test specimens |
| ISO 2818 | Plastics - Preparation of test specimens by machining | For preparing machined test specimens |
| ISO 4599:1986 | Bent strip method (withdrawn) | Predecessor standard replaced by ISO 22088-3:2006 |
Test Application:
Material Development: Evaluating environmental stress cracking resistance of rigid thermoplastics, particularly polyethylene (PE) and polypropylene (PP) materials used in pipes, containers, and cable insulation.
Quality Control: Verifying consistency of ESC resistance in production batches, ensuring materials meet specification requirements.
Material Selection: Comparing different materials for applications exposed to both chemicals and mechanical stress (e.g., chemical storage tanks, outdoor piping systems).
Failure Analysis: Investigating the effect of specific chemical environments on plastic components that have failed in service.
Process Optimization: Evaluating the influence of molding conditions, additives, and polymer structure on final product ESC resistance.
Related products and device
Related Standard
ISO 179: Plastics -- Determination of Charpy impact properties
ASTM D6110: Standard Test Method for Determining the Charpy Impact Resistance of Notched Specimens of Plastics.
ISO 179 specifies a method for determining the Charpy impact strength of plastics under defined conditions. A number of different types of specimen and test configurations are defined. Different test parameters are specified according to the type of material, the type of test specimen and the type of notch.
The method can be used to investigate the behaviour of specified types of specimen under the impact conditions defined and for estimating the brittleness or toughness of specimens within the limitations inherent in the test conditions. It can also be used for the determination of comparative data from similar types of material.
ISO 527-1 Plastics — Determination of tensile properties Part 1: General principles
ISO 527-2 Plastics -- tensile properties -- Part 2: moulding and extrusion
ISO 527-1 covers the test procedures for determining tensile properties of plastics and plastic composites. Tensile properties of plastics that are determined through the practices of ISO 527-1 include tensile strength, tensile modulus and other properties related to stress strain characteristics of plastic materials.
ISO 527-2 specifies the test conditions for determining the tensile properties of moulding and extrusion plastics, based upon the general principles given in ISO 527-1. The methods described in ISO 527-2 are selectively suitable for use with the following range of materials: rigid and semi-rigid thermoplastics moulding, extrusion and cast materials, including compounds filled and reinforced by, for example, short fibres, small rods, plates or granules but excluding textile fibres (see ISO 527-4 and ISO 527-5).
ASTM D882: Standard Test Method for Tensile Properties of Thin Plastic Sheeting
ASTM D882 test methods is used to measure tensile properties including ultimate tensile strength, yield strength, elongation, tensile energy to break and tensile modulus of elasticity of thin plastic sheeting and films. The samples are cut in strips that minimally have to be eight times longer than wide. No dumbbell shape is cut for materials of that thickness. Cut samples need to be free of nicks and other cutting defects since they will have an important impact on the test results variation. The samples are tested in specific conditions of pre-treatment, sample orientation, temperature, humidity, and rate of pulling. ASTM D882 can be used for testing materials thinner than 1mm in thickness.
ISO 4599 standard evaluates the crack resistance of plastic materials under specific environmental conditions through constant pre-strain tests. This performance testing is crucial for assessing the durability and reliability of plastic materials in practical applications.
ASTM D1238 Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer
ASTM D1238 test method test method covers the determination of the rate of extrusion of molten thermoplastic resins using an extrusion plastometer. it is particularly useful for quality control tests on thermoplastics. The data produced by ASTM D1238 test serves to indicate the uniformity of the flow rate of the polymer as made by an individual process. It is not to be used as an indication of uniformity of other properties without valid correlation with data from other tests.
ASTM D412 test methods cover procedures used to evaluate the tensile (tension) properties of vulcanized thermoset rubbers and thermoplastic elastomers. These methods are not applicable to ebonite and similar hard, low elongation materials.
The methods appear as follows:
Test Method A—Dumbbell and Straight Section Specimens
Test Method B—Cut Ring Specimens
Require More Customized Solutions?